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The AEGIS Family of Authenticated Encryption Algorithmsplain textdiff with main

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diff --git a/quantum-attacks/draft-irtf-cfrg-aegis-aead.html b/quantum-attacks/draft-irtf-cfrg-aegis-aead.html new file mode 100644 index 0000000..5c5b5cc --- /dev/null +++ b/quantum-attacks/draft-irtf-cfrg-aegis-aead.html @@ -0,0 +1,3303 @@ + + + + + + +The AEGIS Family of Authenticated Encryption Algorithms + + + + + + + + + + + + + +
+ + + + + + + + + + +
Internet-DraftThe AEGIS Family of Authenticated EncrypOctober 2023
Denis & LucasExpires 22 April 2024[Page]
+
+
+
+
Workgroup:
+
Crypto Forum
+
Internet-Draft:
+
draft-irtf-cfrg-aegis-aead-latest
+
Published:
+
+ +
+
Intended Status:
+
Informational
+
Expires:
+
+
Authors:
+
+
+
F. Denis
+
Fastly Inc.
+
+
+
S. Lucas
+
Individual Contributor
+
+
+
+
+

The AEGIS Family of Authenticated Encryption Algorithms

+
+

Abstract

+

This document describes AEGIS-128L and AEGIS-256, two AES-based authenticated encryption algorithms designed for high-performance applications. +This document is a product of the Crypto Forum Research Group (CFRG). It is not an IETF product and is not a standard.

+
+
+

+Discussion Venues +

+

This note is to be removed before publishing as an RFC.

+

Source for this draft and an issue tracker can be found at + https://github.com/cfrg/draft-irtf-cfrg-aegis-aead.

+
+
+
+

+Status of This Memo +

+

+ This Internet-Draft is submitted in full conformance with the + provisions of BCP 78 and BCP 79.

+

+ Internet-Drafts are working documents of the Internet Engineering Task + Force (IETF). Note that other groups may also distribute working + documents as Internet-Drafts. The list of current Internet-Drafts is + at https://datatracker.ietf.org/drafts/current/.

+

+ Internet-Drafts are draft documents valid for a maximum of six months + and may be updated, replaced, or obsoleted by other documents at any + time. It is inappropriate to use Internet-Drafts as reference + material or to cite them other than as "work in progress."

+

+ This Internet-Draft will expire on 22 April 2024.

+
+
+ +
+
+ ▲

+Table of Contents +

+ +
+
+
+
+

+1. Introduction +

+

This document describes the AEGIS-128L and AEGIS-256 authenticated encryption with associated data (AEAD) algorithms [AEGIS], which were chosen as additional finalists for high-performance applications in the Competition for Authenticated Encryption: Security, Applicability, and Robustness (CAESAR). Whilst AEGIS-128 was selected as a winner for this use case, AEGIS-128L has a better security margin alongside improved performance and AEGIS-256 uses a 256-bit key [LIMS21]. All variants of AEGIS are constructed from the AES encryption round function [FIPS-AES]. This document specifies:

+ +

The AEGIS cipher family offers performance that significantly exceeds that of AES-GCM with hardware support for parallelizable AES block encryption [AEGIS]. Similarly, software implementations can also be faster, although to a lesser extent.

+

Unlike with AES-GCM, nonces can be safely chosen at random with no practical limit when using AEGIS-256. AEGIS-128L also allows for more messages to be safely encrypted when using random nonces.

+

With some existing AEAD schemes, such as AES-GCM, an attacker can generate a ciphertext that successfully decrypts under multiple different keys (a partitioning oracle attack) [LGR21]. This ability to craft a (ciphertext, authentication tag) pair that verifies under multiple keys significantly reduces the number of required interactions with the oracle in order to perform an exhaustive search, making it practical if the key space is small. For example, with password-based encryption, an attacker can guess a large number of passwords at a time by recursively submitting such a ciphertext to an oracle, which speeds up a password search by reducing it to a binary search.

+

In AEGIS, finding distinct (key, nonce) pairs that successfully decrypt a given (associated data, ciphertext, authentication tag) tuple is believed to have a complexity that depends on the tag size. A 128-bit tag provides 64-bit committing security, which is generally acceptable for interactive protocols. With a 256-bit tag, finding a collision becomes impractical.

+

Unlike most other AES-based AEAD constructions, leaking a state does not leak the key nor previous states.

+

Finally, an AEGIS key is not required after the setup phase, and there is no key schedule. Thus, ephemeral keys can be erased from memory before any data has been encrypted or decrypted, mitigating cold boot attacks.

+

Note that an earlier version of Hongjun Wu and Bart Preneel’s paper introducing AEGIS specified AEGIS-128L and AEGIS-256 sporting differences with regards to the computation of the authentication tag and the number of rounds in Finalize() respectively. We follow the specification of [AEGIS] that is current at the time of writing, which can be found in the References section of this document.

+
+
+
+
+

+2. Conventions and Definitions +

+

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, +“MAY”, and “OPTIONAL” in this document are to be interpreted as +described in BCP 14 [RFC2119] [RFC8174] when, and only when, they +appear in all capitals, as shown here.

+

Primitives:

+ +

AEGIS internal functions:

+ +

Input blocks are 256 bits for AEGIS-128L and 128 bits for AEGIS-256.

+

AES blocks:

+ +

AES blocks are always 128 bits in length.

+

Input and output values:

+ +
+
+
+
+

+3. The AEGIS-128L Algorithm +

+

AEGIS-128L has a 1024-bit state, made of eight 128-bit blocks {S0, ...S7}.

+

The parameters for this algorithm, whose meaning is defined in [RFC5116], Section 4 are:

+ +

Distinct associated data inputs, as described in [RFC5116], Section 3 shall be unambiguously encoded as a single input. +It is up to the application to create a structure in the associated data input if needed.

+
+
+

+3.1. Authenticated Encryption +

+
+
+Encrypt(msg, ad, key, nonce)
+
+
+

The Encrypt function encrypts a message and returns the ciphertext along with an authentication tag that verifies the authenticity of the message and associated data, if provided.

+

Security:

+
    +
  • +

    For a given key, the nonce MUST NOT be reused under any circumstances; doing so allows an attacker to recover the internal state.

    +
    • +
  • +

    The key MUST be randomly chosen from a uniform distribution.

    +
    • +
+

Inputs:

+
    +
  • +

    msg: the message to be encrypted (length MUST be less than P_MAX).

    +
    • +
  • +

    ad: the associated data to authenticate (length MUST be less than A_MAX).

    +
    • +
  • +

    key: the encryption key.

    +
    • +
  • +

    nonce: the public nonce.

    +
    • +
+

Outputs:

+
    +
  • +

    ct: the ciphertext.

    +
    • +
  • +

    tag: the authentication tag.

    +
    • +
+

Steps:

+
+
+Init(key, nonce)
+
+ct = {}
+
+ad_blocks = Split(ZeroPad(ad, 256), 256)
+for ai in ad_blocks:
+    Absorb(ai)
+
+msg_blocks = Split(ZeroPad(msg, 256), 256)
+for xi in msg_blocks:
+    ct = ct || Enc(xi)
+
+tag = Finalize(|ad|, |msg|)
+ct = Truncate(ct, |msg|)
+
+return ct and tag
+
+
+
+
+
+
+

+3.2. Authenticated Decryption +

+
+
+Decrypt(ct, tag, ad, key, nonce)
+
+
+

The Decrypt function decrypts a ciphertext, verifies that the authentication tag is correct, and returns the message on success or an error if tag verification failed.

+

Security:

+
    +
  • +

    If tag verification fails, the decrypted message and wrong message authentication tag MUST NOT be given as output. The decrypted message MUST be overwritten with zeros.

    +
    • +
  • +

    The comparison of the input tag with the expected_tag MUST be done in constant time.

    +
    • +
+

Inputs:

+
    +
  • +

    ct: the ciphertext to be decrypted (length MUST be less than C_MAX).

    +
    • +
  • +

    tag: the authentication tag.

    +
    • +
  • +

    ad: the associated data to authenticate (length MUST be less than A_MAX).

    +
    • +
  • +

    key: the encryption key.

    +
    • +
  • +

    nonce: the public nonce.

    +
    • +
+

Outputs:

+
    +
  • +

    Either the decrypted message msg or an error indicating that the authentication tag is invalid for the given inputs.

    +
    • +
+

Steps:

+
+
+Init(key, nonce)
+
+msg = {}
+
+ad_blocks = Split(ZeroPad(ad, 256), 256)
+for ai in ad_blocks:
+    Absorb(ai)
+
+ct_blocks = Split(ct, 256)
+cn = Tail(ct, |ct| mod 256)
+
+for ci in ct_blocks:
+    msg = msg || Dec(ci)
+
+if cn is not empty:
+    msg = msg || DecPartial(cn)
+
+expected_tag = Finalize(|ad|, |msg|)
+
+if CtEq(tag, expected_tag) is False:
+    erase msg
+    return "verification failed" error
+else:
+    return msg
+
+
+
+
+
+
+

+3.3. The Init Function +

+
+
+Init(key, nonce)
+
+
+

The Init function constructs the initial state {S0, ...S7} using the given key and nonce.

+

Inputs:

+
    +
  • +

    key: the encryption key.

    +
    • +
  • +

    nonce: the public nonce.

    +
    • +
+

Defines:

+
    +
  • +

    {S0, ...S7}: the initial state.

    +
    • +
+

Steps:

+
+
+S0 = key ^ nonce
+S1 = C1
+S2 = C0
+S3 = C1
+S4 = key ^ nonce
+S5 = key ^ C0
+S6 = key ^ C1
+S7 = key ^ C0
+
+Repeat(10, Update(nonce, key))
+
+
+
+
+
+
+

+3.4. The Update Function +

+
+
+Update(M0, M1)
+
+
+

The Update function is the core of the AEGIS-128L algorithm. +It updates the state {S0, ...S7} using two 128-bit values.

+

Inputs:

+
    +
  • +

    M0: the first 128-bit block to be absorbed.

    +
    • +
  • +

    M1: the second 128-bit block to be absorbed.

    +
    • +
+

Modifies:

+
    +
  • +

    {S0, ...S7}: the state.

    +
    • +
+

Steps:

+
+
+S'0 = AESRound(S7, S0 ^ M0)
+S'1 = AESRound(S0, S1)
+S'2 = AESRound(S1, S2)
+S'3 = AESRound(S2, S3)
+S'4 = AESRound(S3, S4 ^ M1)
+S'5 = AESRound(S4, S5)
+S'6 = AESRound(S5, S6)
+S'7 = AESRound(S6, S7)
+
+S0  = S'0
+S1  = S'1
+S2  = S'2
+S3  = S'3
+S4  = S'4
+S5  = S'5
+S6  = S'6
+S7  = S'7
+
+
+
+
+
+
+

+3.5. The Absorb Function +

+
+
+Absorb(ai)
+
+
+

The Absorb function absorbs a 256-bit input block ai into the state {S0, ...S7}.

+

Inputs:

+
    +
  • +

    ai: the 256-bit input block.

    +
    • +
+

Steps:

+
+
+t0, t1 = Split(ai, 128)
+Update(t0, t1)
+
+
+
+
+
+
+

+3.6. The Enc Function +

+
+
+Enc(xi)
+
+
+

The Enc function encrypts a 256-bit input block xi using the state {S0, ...S7}.

+

Inputs:

+
    +
  • +

    xi: the 256-bit input block.

    +
    • +
+

Outputs:

+
    +
  • +

    ci: the 256-bit encrypted block.

    +
    • +
+

Steps:

+
+
+z0 = S6 ^ S1 ^ (S2 & S3)
+z1 = S2 ^ S5 ^ (S6 & S7)
+
+t0, t1 = Split(xi, 128)
+out0 = t0 ^ z0
+out1 = t1 ^ z1
+
+Update(t0, t1)
+ci = out0 || out1
+
+return ci
+
+
+
+
+
+
+

+3.7. The Dec Function +

+
+
+Dec(ci)
+
+
+

The Dec function decrypts a 256-bit input block ci using the state {S0, ...S7}.

+

Inputs:

+
    +
  • +

    ci: the 256-bit encrypted block.

    +
    • +
+

Outputs:

+
    +
  • +

    xi: the 256-bit decrypted block.

    +
    • +
+

Steps:

+
+
+z0 = S6 ^ S1 ^ (S2 & S3)
+z1 = S2 ^ S5 ^ (S6 & S7)
+
+t0, t1 = Split(ci, 128)
+out0 = t0 ^ z0
+out1 = t1 ^ z1
+
+Update(out0, out1)
+xi = out0 || out1
+
+return xi
+
+
+
+
+
+
+

+3.8. The DecPartial Function +

+
+
+DecPartial(cn)
+
+
+

The DecPartial function decrypts the last ciphertext bits cn using the state {S0, ...S7} when they do not fill an entire block.

+

Inputs:

+
    +
  • +

    cn: the encrypted input.

    +
    • +
+

Outputs:

+
    +
  • +

    xn: the decryption of cn.

    +
    • +
+

Steps:

+
+
+z0 = S6 ^ S1 ^ (S2 & S3)
+z1 = S2 ^ S5 ^ (S6 & S7)
+
+t0, t1 = Split(ZeroPad(cn, 256), 128)
+out0 = t0 ^ z0
+out1 = t1 ^ z1
+
+xn = Truncate(out0 || out1, |cn|)
+
+v0, v1 = Split(ZeroPad(xn, 256), 128)
+Update(v0, v1)
+
+return xn
+
+
+
+
+
+
+

+3.9. The Finalize Function +

+
+
+Finalize(ad_len_bits, msg_len_bits)
+
+
+

The Finalize function computes a 128- or 256-bit tag that authenticates the message and associated data.

+

Inputs:

+
    +
  • +

    ad_len_bits: the length of the associated data in bits.

    +
    • +
  • +

    msg_len_bits: the length of the message in bits.

    +
    • +
+

Outputs:

+
    +
  • +

    tag: the authentication tag.

    +
    • +
+

Steps:

+
+
+t = S2 ^ (LE64(ad_len_bits) || LE64(msg_len_bits))
+
+Repeat(7, Update(t, t))
+
+if tag_length == 16: # 128 bits
+  tag = S0 ^ S1 ^ S2 ^ S3 ^ S4 ^ S5 ^ S6
+else:                # 256 bits
+  tag = (S0 ^ S1 ^ S2 ^ S3) || (S4 ^ S5 ^ S6 ^ S7)
+
+return tag
+
+
+
+
+
+
+
+
+

+4. The AEGIS-256 Algorithm +

+

AEGIS-256 has a 768-bit state, made of six 128-bit blocks {S0, ...S5}.

+

The parameters for this algorithm, whose meaning is defined in [RFC5116], Section 4 are:

+ +

Distinct associated data inputs, as described in [RFC5116], Section 3 shall be unambiguously encoded as a single input. +It is up to the application to create a structure in the associated data input if needed.

+
+
+

+4.1. Authenticated Encryption +

+
+
+Encrypt(msg, ad, key, nonce)
+
+
+

The Encrypt function encrypts a message and returns the ciphertext along with an authentication tag that verifies the authenticity of the message and associated data, if provided.

+

Security:

+
    +
  • +

    For a given key, the nonce MUST NOT be reused under any circumstances; doing so allows an attacker to recover the internal state.

    +
    • +
  • +

    The key MUST be randomly chosen from a uniform distribution.

    +
    • +
+

Inputs:

+
    +
  • +

    msg: the message to be encrypted (length MUST be less than P_MAX).

    +
    • +
  • +

    ad: the associated data to authenticate (length MUST be less than A_MAX).

    +
    • +
  • +

    key: the encryption key.

    +
    • +
  • +

    nonce: the public nonce.

    +
    • +
+

Outputs:

+
    +
  • +

    ct: the ciphertext.

    +
    • +
  • +

    tag: the authentication tag.

    +
    • +
+

Steps:

+
+
+Init(key, nonce)
+
+ct = {}
+
+ad_blocks = Split(ZeroPad(ad, 128), 128)
+for ai in ad_blocks:
+    Absorb(ai)
+
+msg_blocks = Split(ZeroPad(msg, 128), 128)
+for xi in msg_blocks:
+    ct = ct || Enc(xi)
+
+tag = Finalize(|ad|, |msg|)
+ct = Truncate(ct, |msg|)
+
+return ct and tag
+
+
+
+
+
+
+

+4.2. Authenticated Decryption +

+
+
+Decrypt(ct, tag, ad, key, nonce)
+
+
+

The Decrypt function decrypts a ciphertext, verifies that the authentication tag is correct, and returns the message on success or an error if tag verification failed.

+

Security:

+
    +
  • +

    If tag verification fails, the decrypted message and wrong message authentication tag MUST NOT be given as output. The decrypted message MUST be overwritten with zeros.

    +
    • +
  • +

    The comparison of the input tag with the expected_tag MUST be done in constant time.

    +
    • +
+

Inputs:

+
    +
  • +

    ct: the ciphertext to be decrypted (length MUST be less than C_MAX).

    +
    • +
  • +

    tag: the authentication tag.

    +
    • +
  • +

    ad: the associated data to authenticate (length MUST be less than A_MAX).

    +
    • +
  • +

    key: the encryption key.

    +
    • +
  • +

    nonce: the public nonce.

    +
    • +
+

Outputs:

+
    +
  • +

    Either the decrypted message msg or an error indicating that the authentication tag is invalid for the given inputs.

    +
    • +
+

Steps:

+
+
+Init(key, nonce)
+
+msg = {}
+
+ad_blocks = Split(ZeroPad(ad, 128), 128)
+for ai in ad_blocks:
+    Absorb(ai)
+
+ct_blocks = Split(ZeroPad(ct, 128), 128)
+cn = Tail(ct, |ct| mod 128)
+
+for ci in ct_blocks:
+    msg = msg || Dec(ci)
+
+if cn is not empty:
+    msg = msg || DecPartial(cn)
+
+expected_tag = Finalize(|ad|, |msg|)
+
+if CtEq(tag, expected_tag) is False:
+    erase msg
+    return "verification failed" error
+else:
+    return msg
+
+
+
+
+
+
+

+4.3. The Init Function +

+
+
+Init(key, nonce)
+
+
+

The Init function constructs the initial state {S0, ...S5} using the given key and nonce.

+

Inputs:

+
    +
  • +

    key: the encryption key.

    +
    • +
  • +

    nonce: the public nonce.

    +
    • +
+

Defines:

+
    +
  • +

    {S0, ...S5}: the initial state.

    +
    • +
+

Steps:

+
+
+k0, k1 = Split(key, 128)
+n0, n1 = Split(nonce, 128)
+
+S0 = k0 ^ n0
+S1 = k1 ^ n1
+S2 = C1
+S3 = C0
+S4 = k0 ^ C0
+S5 = k1 ^ C1
+
+Repeat(4,
+  Update(k0)
+  Update(k1)
+  Update(k0 ^ n0)
+  Update(k1 ^ n1)
+)
+
+
+
+
+
+
+

+4.4. The Update Function +

+
+
+Update(M)
+
+
+

The Update function is the core of the AEGIS-256 algorithm. +It updates the state {S0, ...S5} using a 128-bit value.

+

Inputs:

+
    +
  • +

    msg: the block to be absorbed.

    +
    • +
+

Modifies:

+
    +
  • +

    {S0, ...S5}: the state.

    +
    • +
+

Steps:

+
+
+S'0 = AESRound(S5, S0 ^ M)
+S'1 = AESRound(S0, S1)
+S'2 = AESRound(S1, S2)
+S'3 = AESRound(S2, S3)
+S'4 = AESRound(S3, S4)
+S'5 = AESRound(S4, S5)
+
+S0  = S'0
+S1  = S'1
+S2  = S'2
+S3  = S'3
+S4  = S'4
+S5  = S'5
+
+
+
+
+
+
+

+4.5. The Absorb Function +

+
+
+Absorb(ai)
+
+
+

The Absorb function absorbs a 128-bit input block ai into the state {S0, ...S5}.

+

Inputs:

+
    +
  • +

    ai: the input block.

    +
    • +
+

Steps:

+
+
+Update(ai)
+
+
+
+
+
+
+

+4.6. The Enc Function +

+
+
+Enc(xi)
+
+
+

The Enc function encrypts a 128-bit input block xi using the state {S0, ...S5}.

+

Inputs:

+
    +
  • +

    xi: the input block.

    +
    • +
+

Outputs:

+
    +
  • +

    ci: the encrypted input block.

    +
    • +
+

Steps:

+
+
+z = S1 ^ S4 ^ S5 ^ (S2 & S3)
+
+Update(xi)
+
+ci = xi ^ z
+
+return ci
+
+
+
+
+
+
+

+4.7. The Dec Function +

+
+
+Dec(ci)
+
+
+

The Dec function decrypts a 128-bit input block ci using the state {S0, ...S5}.

+

Inputs:

+
    +
  • +

    ci: the encrypted input block.

    +
    • +
+

Outputs:

+
    +
  • +

    xi: the decrypted block.

    +
    • +
+

Steps:

+
+
+z = S1 ^ S4 ^ S5 ^ (S2 & S3)
+
+xi = ci ^ z
+
+Update(xi)
+
+return xi
+
+
+
+
+
+
+

+4.8. The DecPartial Function +

+
+
+DecPartial(cn)
+
+
+

The DecPartial function decrypts the last ciphertext bits cn using the state {S0, ...S5} when they do not fill an entire block.

+

Inputs:

+
    +
  • +

    cn: the encrypted input.

    +
    • +
+

Outputs:

+
    +
  • +

    xn: the decryption of cn.

    +
    • +
+

Steps:

+
+
+z = S1 ^ S4 ^ S5 ^ (S2 & S3)
+
+t = ZeroPad(cn, 128)
+out = t ^ z
+
+xn = Truncate(out, |cn|)
+
+v = ZeroPad(xn, 128)
+Update(v)
+
+return xn
+
+
+
+
+
+
+

+4.9. The Finalize Function +

+
+
+Finalize(ad_len_bits, msg_len_bits)
+
+
+

The Finalize function computes a 128- or 256-bit tag that authenticates the message and associated data.

+

Inputs:

+
    +
  • +

    ad_len_bits: the length of the associated data in bits.

    +
    • +
  • +

    msg_len_bits: the length of the message in bits.

    +
    • +
+

Outputs:

+
    +
  • +

    tag: the authentication tag.

    +
    • +
+

Steps:

+
+
+t = S3 ^ (LE64(ad_len_bits) || LE64(msg_len_bits))
+
+Repeat(7, Update(t))
+
+if tag_length == 16: # 128 bits
+  tag = S0 ^ S1 ^ S2 ^ S3 ^ S4 ^ S5
+else:                # 256 bits
+  tag = (S0 ^ S1 ^ S2) || (S3 ^ S4 ^ S5)
+
+return tag
+
+
+
+
+
+
+
+
+

+5. Encoding (ct, tag) Tuples +

+

Applications MAY keep the ciphertext and the authentication tag in distinct structures or encode both as a single string.

+

In the latter case, the tag MUST immediately follow the ciphertext:

+
+
+combined_ct = ct || tag
+
+
+
+
+
+
+

+6. AEGIS as a Stream Cipher +

+

All AEGIS variants can also be used as stream ciphers.

+
+
+Stream(len, key, nonce)
+
+
+

The Stream function expands a key and an optional nonce into a variable-length, secure keystream.

+

Inputs:

+ +

Outputs:

+ +

Steps:

+
+
+stream, tag = Encrypt(ZeroPad({}, len), {}, key, nonce)
+
+return stream
+
+
+

This is equivalent to encrypting a len all-zero bytes message without associated data, and discarding the authentication tag.

+

Instead of relying on the generic Encrypt function, implementations can skip the finalization step.

+

After initialization, the Update function is called with constant parameters, allowing further optimizations.

+
+
+
+
+

+7. Security Considerations +

+

AEGIS-256 offers 256-bit message security against plaintext and state recovery, whereas AEGIS-128L offers 128-bit security.

+

An authentication tag may verify under multiple keys, nonces, or associated data, but AEGIS is assumed to be key committing in the receiver-binding game, preventing common attacks when used with low-entropy keys such as passwords. Finding distinct keys and/or nonces that successfully verify the same (ad, ct, tag) tuple is expected to require ~264 attempts with a 128-bit authentication tag and ~2128 attempts with a 256-bit tag.

+

However, it is NOT fully committing because the key doesn’t commit to the associated data. As shown in [IR23], with the ability to also alter ad, it is possible to efficiently find multiple keys that will verify the same authenticated ciphertext.

+

Under the assumption that the secret key is unknown to the attacker both AEGIS-128L and AEGIS-256 target 128-bit security against forgery attacks regardless of the tag size.

+

Both algorithms MUST be used in a nonce-respecting setting: for a given key, a nonce MUST only be used once. Failure to do so would immediately reveal the bitwise difference between two messages.

+

If tag verification fails, the decrypted message and wrong message authentication tag MUST NOT be given as output. As shown in the analysis of the (robustness of CAESAR candidates beyond their guarantees)[VV18], even a partial leak of the plaintext without verification would facilitate chosen ciphertext attacks.

+

Every key MUST be randomly chosen from a uniform distribution.

+

The nonce MAY be public or predictable. It can be a counter, the output of a permutation, or a generator with a long period.

+

With AEGIS-128L, random nonces can safely encrypt up to 248 messages using the same key with negligible (~ 2-33, to align with NIST guidelines) collision probability.

+

With AEGIS-256, random nonces can be used with no practical limits.

+

Regardless of the variant, the key and nonce are only required by the Init function; other functions only depend on the resulting state. Therefore, implementations can overwrite ephemeral keys with zeros right after the last Update call of the initialization function.

+

The security of AEGIS against timing and physical attacks is limited by the implementation of the underlying AESRound() function. Failure to implement AESRound() in a fashion safe against timing and physical attacks, such as differential power analysis, timing analysis or fault injection attacks, may lead to leakage of secret key material or state information. The exact mitigations required for timing and physical attacks also depend on the threat model in question.

+

AEGIS is considered secure against guess-and-determine attacks aimed at recovering the state from observed ciphertexts. This resilience extends to quantum adversaries in the Q1 model, wherein quantum attacks do not confer any practical advantage for decrypting previously recorded ciphertexts or achieving key recovery.

+

Security analyses of AEGIS can be found in Chapter 4 of [AEGIS], in [M14], in [ENP19], in [LIMS21], in [JLD21], in [STSI23], in [IR23], and in [BS23].

+
+
+
+
+

+8. IANA Considerations +

+

IANA has assigned the following identifiers in the AEAD Algorithms Registry:

+ + + + + + + + + + + + + + + + + + +
+Table 1: +AEGIS entries in the AEAD Algorithms Registry +
Algorithm NameID
+ AEAD_AEGIS128L + + 32 +
+ AEAD_AEGIS256 + + 33 +
+

IANA has also assigned the following TLS cipher suites in the TLS Cipher Suite Registry:

+ + + + + + + + + + + + + + + + + + +
+Table 2: +AEGIS entries in the TLS Cipher Suite Registry +
Cipher Suite NameValue
+ TLS_AEGIS_256_SHA384 + + {0x13,0x06} +
+ TLS_AEGIS_128L_SHA256 + + {0x13,0x07} +
+

A 128-bit tag length must be used with these cipher suites.

+

IANA is requested to update the references of these entries to refer to the final version of this document.

+
+
+
+
+

+9. QUIC and DTLS 1.3 Header Protection +

+
+
+

+9.1. DTLS 1.3 Record Number Encryption +

+

In DTLS 1.3, record sequence numbers are encrypted as specified in [RFC9147].

+

For AEGIS-128L and AEGIS-256, the mask is generated using the AEGIS Stream function with:

+
    +
  • +

    a 128-bit tag length

    +
    • +
  • +

    sn_key, as defined in Section 4.2.3 of [RFC9147]

    +
    • +
  • +

    ciphertext[0..16]: the first 16 bytes of the DTLS ciphertext

    +
    • +
  • +

    nonce_len: the AEGIS nonce length

    +
    • +
+

The 5-byte mask is computed as follows:

+
+
+mask = Stream(5, sn_key, ZeroPad(ciphertext[0..16], nonce_len))
+
+
+
+
+
+
+

+9.2. QUIC Header Protection +

+

In QUIC, parts of the QUIC packet headers are encrypted as specified in [RFC9001].

+

For AEGIS-128L and AEGIS-256, the mask is generated using the AEGIS Encrypt function with:

+
    +
  • +

    a 128-bit tag length

    +
    • +
  • +

    hp_key, as defined in Section 5.4 of [RFC9001]

    +
    • +
  • +

    sample: the 16 bytes QUIC ciphertext sample

    +
    • +
  • +

    nonce_len: the AEGIS nonce length

    +
    • +
+

The mask is computed as follows:

+
+
+mask = Encrypt("", "", hp_key, ZeroPad(sample, nonce_len))
+
+
+
+
+
+
+
+

+10. References +

+
+
+

+10.1. Normative References +

+
+
[FIPS-AES]
+
+NIST, "Advanced encryption standard (AES)", NIST Federal Information Processing Standards Publications 197, DOI 10.6028/NIST.FIPS.197, , <https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf>.
+
+
[RFC2119]
+
+Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
+
+
[RFC5116]
+
+McGrew, D., "An Interface and Algorithms for Authenticated Encryption", RFC 5116, DOI 10.17487/RFC5116, , <https://www.rfc-editor.org/rfc/rfc5116>.
+
+
[RFC8174]
+
+Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
+
+
+
+
+
+
+

+10.2. Informative References +

+
+
[AEGIS]
+
+Wu, H. and B. Preneel, "AEGIS: A Fast Authenticated Encryption Algorithm (v1.1)", , <https://competitions.cr.yp.to/round3/aegisv11.pdf>.
+
+
[BS23]
+
+Bonnetain, X. and A. Schrottenloher, "Single-query Quantum Hidden Shift Attacks", Cryptology ePrint Archive, Paper 2023/1306, , <https://eprint.iacr.org/2023/1306>.
+
+
[ENP19]
+
+Eichlseder, M., Nageler, M., and R. Primas, "Analyzing the Linear Keystream Biases in AEGIS", IACR Transactions on Symmetric Cryptology, 2019(4), pp. 348–368, DOI 10.13154/tosc.v2019.i4.348-368, , <https://doi.org/10.13154/tosc.v2019.i4.348-368>.
+
+
[IR23]
+
+Isobe, T. and M. Rahman, "Key Committing Security Analysis of AEGIS", Cryptology ePrint Archive, Paper 2023/1495, , <https://eprint.iacr.org/2023/1495>.
+
+
[JLD21]
+
+Jiao, L., Li, Y., and S. Du, "Guess-and-Determine Attacks on AEGIS", The Computer Journal, vol 65, 2022(8), pp. 2221–2230, DOI 10.1093/comjnl/bxab059, , <https://doi.org/10.1093/comjnl/bxab059>.
+
+
[LGR21]
+
+Len, J., Grubbs, P., and T. Ristenpart, "Partitioning Oracle Attacks", 30th USENIX Security Symposium (USENIX Security 21), pp. 195–212, , <https://www.usenix.org/conference/usenixsecurity21/presentation/len>.
+
+
[LIMS21]
+
+Liu, F., Isobe, T., Meier, W., and K. Sakamoto, "Weak Keys in Reduced AEGIS and Tiaoxin", IACR Transactions on Symmetric Cryptology, 2021(2), pp. 104–139, DOI 10.46586/tosc.v2021.i2.104-139, , <https://doi.org/10.46586/tosc.v2021.i2.104-139>.
+
+
[M14]
+
+Minaud, B., "Linear Biases in AEGIS Keystream", Selected Areas in Cryptography. SAC 2014. Lecture Notes in Computer Science, vol 8781, pp. 290–305, DOI 10.1007/978-3-319-13051-4_18, , <https://doi.org/10.1007/978-3-319-13051-4_18>.
+
+
[STSI23]
+
+Shiraya, T., Takeuchi, N., Sakamoto, K., and T. Isobe, "MILP-based security evaluation for AEGIS/Tiaoxin-346/Rocca", IET Information Security, vol 17, 2023(3), pp. 458-467, DOI 10.1049/ise2.12109, , <https://doi.org/10.1049/ise2.12109>.
+
+
[VV18]
+
+Vaudenay, S. and D. Vizár, "Can Caesar Beat Galois?", Applied Cryptography and Network Security. ACNS 2018. Lecture Notes in Computer Science, vol 10892, pp. 476–494, DOI 10.1007/978-3-319-93387-0_25, , <https://doi.org/10.1007/978-3-319-93387-0_25>.
+
+
+
+
+
+
+
+

+Appendix A. Test Vectors +

+
+
+

+A.1. AESRound Test Vector +

+
+
+in   : 000102030405060708090a0b0c0d0e0f
+
+rk   : 101112131415161718191a1b1c1d1e1f
+
+out  : 7a7b4e5638782546a8c0477a3b813f43
+
+
+
+
+
+
+

+A.2. AEGIS-128L Test Vectors +

+
+
+

+A.2.1. Update Test Vector +

+
+
+S0   : 9b7e60b24cc873ea894ecc07911049a3
+S1   : 330be08f35300faa2ebf9a7b0d274658
+S2   : 7bbd5bd2b049f7b9b515cf26fbe7756c
+S3   : c35a00f55ea86c3886ec5e928f87db18
+S4   : 9ebccafce87cab446396c4334592c91f
+S5   : 58d83e31f256371e60fc6bb257114601
+S6   : 1639b56ea322c88568a176585bc915de
+S7   : 640818ffb57dc0fbc2e72ae93457e39a
+
+M0   : 033e6975b94816879e42917650955aa0
+M1   : 033e6975b94816879e42917650955aa0
+
+After Update:
+S0   : 596ab773e4433ca0127c73f60536769d
+S1   : 790394041a3d26ab697bde865014652d
+S2   : 38cf49e4b65248acd533041b64dd0611
+S3   : 16d8e58748f437bfff1797f780337cee
+S4   : 69761320f7dd738b281cc9f335ac2f5a
+S5   : a21746bb193a569e331e1aa985d0d729
+S6   : 09d714e6fcf9177a8ed1cde7e3d259a6
+S7   : 61279ba73167f0ab76f0a11bf203bdff
+
+
+
+
+
+
+

+A.2.2. Test Vector 1 +

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    :
+
+msg   : 00000000000000000000000000000000
+
+ct    : c1c0e58bd913006feba00f4b3cc3594e
+
+tag128: abe0ece80c24868a226a35d16bdae37a
+
+tag256: 25835bfbb21632176cf03840687cb968
+        cace4617af1bd0f7d064c639a5c79ee4
+
+
+
+
+
+
+

+A.2.3. Test Vector 2 +

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    :
+
+msg   :
+
+ct    :
+
+tag128: c2b879a67def9d74e6c14f708bbcc9b4
+
+tag256: 1360dc9db8ae42455f6e5b6a9d488ea4
+        f2184c4e12120249335c4ee84bafe25d
+
+
+
+
+
+
+

+A.2.4. Test Vector 3 +

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    : 0001020304050607
+
+msg   : 000102030405060708090a0b0c0d0e0f
+        101112131415161718191a1b1c1d1e1f
+
+ct    : 79d94593d8c2119d7e8fd9b8fc77845c
+        5c077a05b2528b6ac54b563aed8efe84
+
+tag128: cc6f3372f6aa1bb82388d695c3962d9a
+
+tag256: 022cb796fe7e0ae1197525ff67e30948
+        4cfbab6528ddef89f17d74ef8ecd82b3
+
+
+
+
+
+
+

+A.2.5. Test Vector 4 +

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    : 0001020304050607
+
+msg   : 000102030405060708090a0b0c0d
+
+ct    : 79d94593d8c2119d7e8fd9b8fc77
+
+tag128: 5c04b3dba849b2701effbe32c7f0fab7
+
+tag256: 86f1b80bfb463aba711d15405d094baf
+        4a55a15dbfec81a76f35ed0b9c8b04ac
+
+
+
+
+
+
+

+A.2.6. Test Vector 5 +

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    : 000102030405060708090a0b0c0d0e0f
+        101112131415161718191a1b1c1d1e1f
+        20212223242526272829
+
+msg   : 101112131415161718191a1b1c1d1e1f
+        202122232425262728292a2b2c2d2e2f
+        3031323334353637
+
+ct    : b31052ad1cca4e291abcf2df3502e6bd
+        b1bfd6db36798be3607b1f94d34478aa
+        7ede7f7a990fec10
+
+tag128: 7542a745733014f9474417b337399507
+
+tag256: b91e2947a33da8bee89b6794e647baf0
+        fc835ff574aca3fc27c33be0db2aff98
+
+
+
+
+
+
+

+A.2.7. Test Vector 6 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10000200000000000000000000000000
+
+nonce : 10010000000000000000000000000000
+
+ad    : 0001020304050607
+
+ct    : 79d94593d8c2119d7e8fd9b8fc77
+
+tag128: 5c04b3dba849b2701effbe32c7f0fab7
+
+tag256: 86f1b80bfb463aba711d15405d094baf
+        4a55a15dbfec81a76f35ed0b9c8b04ac
+
+
+
+
+
+
+

+A.2.8. Test Vector 7 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    : 0001020304050607
+
+ct    : 79d94593d8c2119d7e8fd9b8fc78
+
+tag128: 5c04b3dba849b2701effbe32c7f0fab7
+
+tag256: 86f1b80bfb463aba711d15405d094baf
+        4a55a15dbfec81a76f35ed0b9c8b04ac
+
+
+
+
+
+
+

+A.2.9. Test Vector 8 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    : 0001020304050608
+
+ct    : 79d94593d8c2119d7e8fd9b8fc77
+
+tag128: 5c04b3dba849b2701effbe32c7f0fab7
+
+tag256: 86f1b80bfb463aba711d15405d094baf
+        4a55a15dbfec81a76f35ed0b9c8b04ac
+
+
+
+
+
+
+

+A.2.10. Test Vector 9 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10010000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+
+ad    : 0001020304050607
+
+ct    : 79d94593d8c2119d7e8fd9b8fc77
+
+tag128: 6c04b3dba849b2701effbe32c7f0fab8
+
+tag256: 86f1b80bfb463aba711d15405d094baf
+        4a55a15dbfec81a76f35ed0b9c8b04ad
+
+
+
+
+
+
+
+
+

+A.3. AEGIS-256 Test Vectors +

+
+
+

+A.3.1. Update Test Vector +

+
+
+S0   : 1fa1207ed76c86f2c4bb40e8b395b43e
+S1   : b44c375e6c1e1978db64bcd12e9e332f
+S2   : 0dab84bfa9f0226432ff630f233d4e5b
+S3   : d7ef65c9b93e8ee60c75161407b066e7
+S4   : a760bb3da073fbd92bdc24734b1f56fb
+S5   : a828a18d6a964497ac6e7e53c5f55c73
+
+M    : b165617ed04ab738afb2612c6d18a1ec
+
+After Update:
+S0   : e6bc643bae82dfa3d991b1b323839dcd
+S1   : 648578232ba0f2f0a3677f617dc052c3
+S2   : ea788e0e572044a46059212dd007a789
+S3   : 2f1498ae19b80da13fba698f088a8590
+S4   : a54c2ee95e8c2a2c3dae2ec743ae6b86
+S5   : a3240fceb68e32d5d114df1b5363ab67
+
+
+
+
+
+
+

+A.3.2. Test Vector 1 +

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    :
+
+msg   : 00000000000000000000000000000000
+
+ct    : 754fc3d8c973246dcc6d741412a4b236
+
+tag128: 3fe91994768b332ed7f570a19ec5896e
+
+tag256: 1181a1d18091082bf0266f66297d167d
+        2e68b845f61a3b0527d31fc7b7b89f13
+
+
+
+
+
+
+

+A.3.3. Test Vector 2 +

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    :
+
+msg   :
+
+ct    :
+
+tag128: e3def978a0f054afd1e761d7553afba3
+
+tag256: 6a348c930adbd654896e1666aad67de9
+        89ea75ebaa2b82fb588977b1ffec864a
+
+
+
+
+
+
+

+A.3.4. Test Vector 3 +

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 0001020304050607
+
+msg   : 000102030405060708090a0b0c0d0e0f
+        101112131415161718191a1b1c1d1e1f
+
+ct    : f373079ed84b2709faee373584585d60
+        accd191db310ef5d8b11833df9dec711
+
+tag128: 8d86f91ee606e9ff26a01b64ccbdd91d
+
+tag256: b7d28d0c3c0ebd409fd22b4416050307
+        3a547412da0854bfb9723020dab8da1a
+
+
+
+
+
+
+

+A.3.5. Test Vector 4 +

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 0001020304050607
+
+msg   : 000102030405060708090a0b0c0d
+
+ct    : f373079ed84b2709faee37358458
+
+tag128: c60b9c2d33ceb058f96e6dd03c215652
+
+tag256: 8c1cc703c81281bee3f6d9966e14948b
+        4a175b2efbdc31e61a98b4465235c2d9
+
+
+
+
+
+
+

+A.3.6. Test Vector 5 +

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 000102030405060708090a0b0c0d0e0f
+        101112131415161718191a1b1c1d1e1f
+        20212223242526272829
+
+msg   : 101112131415161718191a1b1c1d1e1f
+        202122232425262728292a2b2c2d2e2f
+        3031323334353637
+
+ct    : 57754a7d09963e7c787583a2e7b859bb
+        24fa1e04d49fd550b2511a358e3bca25
+        2a9b1b8b30cc4a67
+
+tag128: ab8a7d53fd0e98d727accca94925e128
+
+tag256: a3aca270c006094d71c20e6910b5161c
+        0826df233d08919a566ec2c05990f734
+
+
+
+
+
+
+

+A.3.7. Test Vector 6 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 0001020304050607
+
+ct    : f373079ed84b2709faee37358458
+
+tag128: c60b9c2d33ceb058f96e6dd03c215652
+
+tag256: 8c1cc703c81281bee3f6d9966e14948b
+        4a175b2efbdc31e61a98b4465235c2d9
+
+
+
+
+
+
+

+A.3.8. Test Vector 7 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 0001020304050607
+
+ct    : f373079ed84b2709faee37358459
+
+tag128: c60b9c2d33ceb058f96e6dd03c215652
+
+tag256: 8c1cc703c81281bee3f6d9966e14948b
+        4a175b2efbdc31e61a98b4465235c2d9
+
+
+
+
+
+
+

+A.3.9. Test Vector 8 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 0001020304050608
+
+ct    : f373079ed84b2709faee37358458
+
+tag128: c60b9c2d33ceb058f96e6dd03c215652
+
+tag256: 8c1cc703c81281bee3f6d9966e14948b
+        4a175b2efbdc31e61a98b4465235c2d9
+
+
+
+
+
+
+

+A.3.10. Test Vector 9 +

+

This test MUST return a “verification failed” error.

+
+
+key   : 10010000000000000000000000000000
+        00000000000000000000000000000000
+
+nonce : 10000200000000000000000000000000
+        00000000000000000000000000000000
+
+ad    : 0001020304050607
+
+ct    : f373079ed84b2709faee37358458
+
+tag128: c60b9c2d33ceb058f96e6dd03c215653
+
+tag256: 8c1cc703c81281bee3f6d9966e14948b
+        4a175b2efbdc31e61a98b4465235c2da
+
+
+
+
+
+
+
+
+
+
+

+Acknowledgments +

+

The AEGIS authenticated encryption algorithm was invented by Hongjun Wu and Bart Preneel.

+

The round function leverages the AES permutation invented by Joan Daemen and Vincent Rijmen. They also authored the Pelican MAC that partly motivated the design of the AEGIS MAC.

+

We would like to thank the following individuals for their contributions:

+ +
+
+
+
+

+Authors' Addresses +

+
+
Frank Denis
+
Fastly Inc.
+ +
+
+
Samuel Lucas
+
Individual Contributor
+ +
+
+
+ + + diff --git a/quantum-attacks/draft-irtf-cfrg-aegis-aead.txt b/quantum-attacks/draft-irtf-cfrg-aegis-aead.txt new file mode 100644 index 0000000..6af6655 --- /dev/null +++ b/quantum-attacks/draft-irtf-cfrg-aegis-aead.txt @@ -0,0 +1,1658 @@ + + + + +Crypto Forum F. Denis +Internet-Draft Fastly Inc. +Intended status: Informational S. Lucas +Expires: 22 April 2024 Individual Contributor + 20 October 2023 + + + The AEGIS Family of Authenticated Encryption Algorithms + draft-irtf-cfrg-aegis-aead-latest + +Abstract + + This document describes AEGIS-128L and AEGIS-256, two AES-based + authenticated encryption algorithms designed for high-performance + applications. This document is a product of the Crypto Forum + Research Group (CFRG). It is not an IETF product and is not a + standard. + +Discussion Venues + + This note is to be removed before publishing as an RFC. + + Source for this draft and an issue tracker can be found at + https://github.com/cfrg/draft-irtf-cfrg-aegis-aead. + +Status of This Memo + + This Internet-Draft is submitted in full conformance with the + provisions of BCP 78 and BCP 79. + + Internet-Drafts are working documents of the Internet Engineering + Task Force (IETF). Note that other groups may also distribute + working documents as Internet-Drafts. The list of current Internet- + Drafts is at https://datatracker.ietf.org/drafts/current/. + + Internet-Drafts are draft documents valid for a maximum of six months + and may be updated, replaced, or obsoleted by other documents at any + time. It is inappropriate to use Internet-Drafts as reference + material or to cite them other than as "work in progress." + + This Internet-Draft will expire on 22 April 2024. + +Copyright Notice + + Copyright (c) 2023 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents (https://trustee.ietf.org/ + license-info) in effect on the date of publication of this document. + Please review these documents carefully, as they describe your rights + and restrictions with respect to this document. + +Table of Contents + + 1. Introduction + 2. Conventions and Definitions + 3. The AEGIS-128L Algorithm + 3.1. Authenticated Encryption + 3.2. Authenticated Decryption + 3.3. The Init Function + 3.4. The Update Function + 3.5. The Absorb Function + 3.6. The Enc Function + 3.7. The Dec Function + 3.8. The DecPartial Function + 3.9. The Finalize Function + 4. The AEGIS-256 Algorithm + 4.1. Authenticated Encryption + 4.2. Authenticated Decryption + 4.3. The Init Function + 4.4. The Update Function + 4.5. The Absorb Function + 4.6. The Enc Function + 4.7. The Dec Function + 4.8. The DecPartial Function + 4.9. The Finalize Function + 5. Encoding (ct, tag) Tuples + 6. AEGIS as a Stream Cipher + 7. Security Considerations + 8. IANA Considerations + 9. QUIC and DTLS 1.3 Header Protection + 9.1. DTLS 1.3 Record Number Encryption + 9.2. QUIC Header Protection + 10. References + 10.1. Normative References + 10.2. Informative References + Appendix A. Test Vectors + A.1. AESRound Test Vector + A.2. AEGIS-128L Test Vectors + A.2.1. Update Test Vector + A.2.2. Test Vector 1 + A.2.3. Test Vector 2 + A.2.4. Test Vector 3 + A.2.5. Test Vector 4 + A.2.6. Test Vector 5 + A.2.7. Test Vector 6 + A.2.8. Test Vector 7 + A.2.9. Test Vector 8 + A.2.10. Test Vector 9 + A.3. AEGIS-256 Test Vectors + A.3.1. Update Test Vector + A.3.2. Test Vector 1 + A.3.3. Test Vector 2 + A.3.4. Test Vector 3 + A.3.5. Test Vector 4 + A.3.6. Test Vector 5 + A.3.7. Test Vector 6 + A.3.8. Test Vector 7 + A.3.9. Test Vector 8 + A.3.10. Test Vector 9 + Acknowledgments + Authors' Addresses + +1. Introduction + + This document describes the AEGIS-128L and AEGIS-256 authenticated + encryption with associated data (AEAD) algorithms [AEGIS], which were + chosen as additional finalists for high-performance applications in + the Competition for Authenticated Encryption: Security, + Applicability, and Robustness (CAESAR). Whilst AEGIS-128 was + selected as a winner for this use case, AEGIS-128L has a better + security margin alongside improved performance and AEGIS-256 uses a + 256-bit key [LIMS21]. All variants of AEGIS are constructed from the + AES encryption round function [FIPS-AES]. This document specifies: + + * AEGIS-128L, which has a 128-bit key, a 128-bit nonce, a 1024-bit + state, a 128- or 256-bit authentication tag, and processes 256-bit + input blocks. + + * AEGIS-256, which has a 256-bit key, a 256-bit nonce, a 768-bit + state, a 128- or 256-bit authentication tag, and processes 128-bit + input blocks. + + The AEGIS cipher family offers performance that significantly exceeds + that of AES-GCM with hardware support for parallelizable AES block + encryption [AEGIS]. Similarly, software implementations can also be + faster, although to a lesser extent. + + Unlike with AES-GCM, nonces can be safely chosen at random with no + practical limit when using AEGIS-256. AEGIS-128L also allows for + more messages to be safely encrypted when using random nonces. + + With some existing AEAD schemes, such as AES-GCM, an attacker can + generate a ciphertext that successfully decrypts under multiple + different keys (a partitioning oracle attack) [LGR21]. This ability + to craft a (ciphertext, authentication tag) pair that verifies under + multiple keys significantly reduces the number of required + interactions with the oracle in order to perform an exhaustive + search, making it practical if the key space is small. For example, + with password-based encryption, an attacker can guess a large number + of passwords at a time by recursively submitting such a ciphertext to + an oracle, which speeds up a password search by reducing it to a + binary search. + + In AEGIS, finding distinct (key, nonce) pairs that successfully + decrypt a given (associated data, ciphertext, authentication tag) + tuple is believed to have a complexity that depends on the tag size. + A 128-bit tag provides 64-bit committing security, which is generally + acceptable for interactive protocols. With a 256-bit tag, finding a + collision becomes impractical. + + Unlike most other AES-based AEAD constructions, leaking a state does + not leak the key nor previous states. + + Finally, an AEGIS key is not required after the setup phase, and + there is no key schedule. Thus, ephemeral keys can be erased from + memory before any data has been encrypted or decrypted, mitigating + cold boot attacks. + + Note that an earlier version of Hongjun Wu and Bart Preneel’s paper + introducing AEGIS specified AEGIS-128L and AEGIS-256 sporting + differences with regards to the computation of the authentication tag + and the number of rounds in Finalize() respectively. We follow the + specification of [AEGIS] that is current at the time of writing, + which can be found in the References section of this document. + +2. Conventions and Definitions + + The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, + “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and + “OPTIONAL” in this document are to be interpreted as described in + BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all + capitals, as shown here. + + Primitives: + + * {}: an empty bit array. + + * |x|: the length of x in bits. + + * a ^ b: the bitwise exclusive OR operation between a and b. + + * a & b: the bitwise AND operation between a and b. + + * a || b: the concatenation of a and b. + + * a mod b: the remainder of the Euclidean division between a as the + dividend and b as the divisor. + + * LE64(x): the little-endian encoding of unsigned 64-bit integer x. + + * ZeroPad(x, n): padding operation. Trailing zeros are concatenated + to x until the total length is a multiple of n bits. + + * Truncate(x, n): truncation operation. The first n bits of x are + kept. + + * Split(x, n): splitting operation. x is split into n-bit blocks, + ignoring partial blocks. + + * Tail(x, n): returns the last n bits of x. + + * AESRound(in, rk): a single round of the AES encryption round + function, which is the composition of the SubBytes, ShiftRows, + MixColums and AddRoundKey transformations, as defined in section 5 + of [FIPS-AES]. Here, in is the 128-bit AES input state, and rk is + the 128-bit round key. + + * Repeat(n, F): n sequential evaluations of the function F. + + * CtEq(a, b): compares a and b in constant-time, returning True for + an exact match, False otherwise. + + AEGIS internal functions: + + * Update(M0, M1): the state update function. + + * Init(key, nonce): the initialization function. + + * Absorb(ai): the input block absorption function. + + * Enc(xi): the input block encryption function. + + * Dec(ci): the input block decryption function. + + * DecPartial(cn): the input block decryption function for the last + ciphertext bits when they do not fill an entire block. + + * Finalize(ad_len_bits, msg_len_bits): the authentication tag + generation function. + + Input blocks are 256 bits for AEGIS-128L and 128 bits for AEGIS-256. + + AES blocks: + + * Si: the i-th AES block of the current state. + + * S'i: the i-th AES block of the next state. + + * {Si, ...Sj}: the vector of the i-th AES block of the current state + to the j-th block of the current state. + + * C0: an AES block built from the following bytes in hexadecimal + format: { 0x00, 0x01, 0x01, 0x02, 0x03, 0x05, 0x08, 0x0d, 0x15, + 0x22, 0x37, 0x59, 0x90, 0xe9, 0x79, 0x62 }. + + * C1: an AES block built from the following bytes in hexadecimal + format: { 0xdb, 0x3d, 0x18, 0x55, 0x6d, 0xc2, 0x2f, 0xf1, 0x20, + 0x11, 0x31, 0x42, 0x73, 0xb5, 0x28, 0xdd }. + + AES blocks are always 128 bits in length. + + Input and output values: + + * key: the encryption key (128 bits for AEGIS-128L, 256 bits for + AEGIS-256). + + * nonce: the public nonce (128 bits for AEGIS-128L, 256 bits for + AEGIS-256). + + * ad: the associated data. + + * msg: the plaintext. + + * ct: the ciphertext. + + * tag: the authentication tag (128 or 256 bits). + +3. The AEGIS-128L Algorithm + + AEGIS-128L has a 1024-bit state, made of eight 128-bit blocks {S0, + ...S7}. + + The parameters for this algorithm, whose meaning is defined in + [RFC5116], Section 4 are: + + * K_LEN (key length) is 16 octets (128 bits). + + * P_MAX (maximum length of the plaintext) is 2^61 octets (2^64 + bits). + + * A_MAX (maximum length of the associated data) is 2^61 octets (2^64 + bits). + + * N_MIN (minimum nonce length) = N_MAX (maximum nonce length) = 16 + octets (128 bits). + + * C_MAX (maximum ciphertext length) = P_MAX + tag length = 2^61 + 16 + or 32 octets (2^64 + 128 or 256 bits). + + Distinct associated data inputs, as described in [RFC5116], Section 3 + shall be unambiguously encoded as a single input. It is up to the + application to create a structure in the associated data input if + needed. + +3.1. Authenticated Encryption + + Encrypt(msg, ad, key, nonce) + + The Encrypt function encrypts a message and returns the ciphertext + along with an authentication tag that verifies the authenticity of + the message and associated data, if provided. + + Security: + + * For a given key, the nonce MUST NOT be reused under any + circumstances; doing so allows an attacker to recover the internal + state. + + * The key MUST be randomly chosen from a uniform distribution. + + Inputs: + + * msg: the message to be encrypted (length MUST be less than P_MAX). + + * ad: the associated data to authenticate (length MUST be less than + A_MAX). + + * key: the encryption key. + + * nonce: the public nonce. + + Outputs: + + * ct: the ciphertext. + + * tag: the authentication tag. + + Steps: + + Init(key, nonce) + + ct = {} + + ad_blocks = Split(ZeroPad(ad, 256), 256) + for ai in ad_blocks: + Absorb(ai) + + msg_blocks = Split(ZeroPad(msg, 256), 256) + for xi in msg_blocks: + ct = ct || Enc(xi) + + tag = Finalize(|ad|, |msg|) + ct = Truncate(ct, |msg|) + + return ct and tag + +3.2. Authenticated Decryption + + Decrypt(ct, tag, ad, key, nonce) + + The Decrypt function decrypts a ciphertext, verifies that the + authentication tag is correct, and returns the message on success or + an error if tag verification failed. + + Security: + + * If tag verification fails, the decrypted message and wrong message + authentication tag MUST NOT be given as output. The decrypted + message MUST be overwritten with zeros. + + * The comparison of the input tag with the expected_tag MUST be done + in constant time. + + Inputs: + + * ct: the ciphertext to be decrypted (length MUST be less than + C_MAX). + + * tag: the authentication tag. + + * ad: the associated data to authenticate (length MUST be less than + A_MAX). + + * key: the encryption key. + + * nonce: the public nonce. + + Outputs: + + * Either the decrypted message msg or an error indicating that the + authentication tag is invalid for the given inputs. + + Steps: + + Init(key, nonce) + + msg = {} + + ad_blocks = Split(ZeroPad(ad, 256), 256) + for ai in ad_blocks: + Absorb(ai) + + ct_blocks = Split(ct, 256) + cn = Tail(ct, |ct| mod 256) + + for ci in ct_blocks: + msg = msg || Dec(ci) + + if cn is not empty: + msg = msg || DecPartial(cn) + + expected_tag = Finalize(|ad|, |msg|) + + if CtEq(tag, expected_tag) is False: + erase msg + return "verification failed" error + else: + return msg + +3.3. The Init Function + + Init(key, nonce) + + The Init function constructs the initial state {S0, ...S7} using the + given key and nonce. + + Inputs: + + * key: the encryption key. + + * nonce: the public nonce. + + Defines: + + * {S0, ...S7}: the initial state. + + Steps: + + S0 = key ^ nonce + S1 = C1 + S2 = C0 + S3 = C1 + S4 = key ^ nonce + S5 = key ^ C0 + S6 = key ^ C1 + S7 = key ^ C0 + + Repeat(10, Update(nonce, key)) + +3.4. The Update Function + + Update(M0, M1) + + The Update function is the core of the AEGIS-128L algorithm. It + updates the state {S0, ...S7} using two 128-bit values. + + Inputs: + + * M0: the first 128-bit block to be absorbed. + + * M1: the second 128-bit block to be absorbed. + + Modifies: + + * {S0, ...S7}: the state. + + Steps: + + S'0 = AESRound(S7, S0 ^ M0) + S'1 = AESRound(S0, S1) + S'2 = AESRound(S1, S2) + S'3 = AESRound(S2, S3) + S'4 = AESRound(S3, S4 ^ M1) + S'5 = AESRound(S4, S5) + S'6 = AESRound(S5, S6) + S'7 = AESRound(S6, S7) + + S0 = S'0 + S1 = S'1 + S2 = S'2 + S3 = S'3 + S4 = S'4 + S5 = S'5 + S6 = S'6 + S7 = S'7 + +3.5. The Absorb Function + + Absorb(ai) + + The Absorb function absorbs a 256-bit input block ai into the state + {S0, ...S7}. + + Inputs: + + * ai: the 256-bit input block. + + Steps: + + t0, t1 = Split(ai, 128) + Update(t0, t1) + +3.6. The Enc Function + + Enc(xi) + + The Enc function encrypts a 256-bit input block xi using the state + {S0, ...S7}. + + Inputs: + + * xi: the 256-bit input block. + + Outputs: + + * ci: the 256-bit encrypted block. + + Steps: + + z0 = S6 ^ S1 ^ (S2 & S3) + z1 = S2 ^ S5 ^ (S6 & S7) + + t0, t1 = Split(xi, 128) + out0 = t0 ^ z0 + out1 = t1 ^ z1 + + Update(t0, t1) + ci = out0 || out1 + + return ci + +3.7. The Dec Function + + Dec(ci) + + The Dec function decrypts a 256-bit input block ci using the state + {S0, ...S7}. + + Inputs: + + * ci: the 256-bit encrypted block. + + Outputs: + + * xi: the 256-bit decrypted block. + + Steps: + + z0 = S6 ^ S1 ^ (S2 & S3) + z1 = S2 ^ S5 ^ (S6 & S7) + + t0, t1 = Split(ci, 128) + out0 = t0 ^ z0 + out1 = t1 ^ z1 + + Update(out0, out1) + xi = out0 || out1 + + return xi + +3.8. The DecPartial Function + + DecPartial(cn) + + The DecPartial function decrypts the last ciphertext bits cn using + the state {S0, ...S7} when they do not fill an entire block. + + Inputs: + + * cn: the encrypted input. + + Outputs: + + * xn: the decryption of cn. + + Steps: + + z0 = S6 ^ S1 ^ (S2 & S3) + z1 = S2 ^ S5 ^ (S6 & S7) + + t0, t1 = Split(ZeroPad(cn, 256), 128) + out0 = t0 ^ z0 + out1 = t1 ^ z1 + + xn = Truncate(out0 || out1, |cn|) + + v0, v1 = Split(ZeroPad(xn, 256), 128) + Update(v0, v1) + + return xn + +3.9. The Finalize Function + + Finalize(ad_len_bits, msg_len_bits) + + The Finalize function computes a 128- or 256-bit tag that + authenticates the message and associated data. + + Inputs: + + * ad_len_bits: the length of the associated data in bits. + + * msg_len_bits: the length of the message in bits. + + Outputs: + + * tag: the authentication tag. + + Steps: + + t = S2 ^ (LE64(ad_len_bits) || LE64(msg_len_bits)) + + Repeat(7, Update(t, t)) + + if tag_length == 16: # 128 bits + tag = S0 ^ S1 ^ S2 ^ S3 ^ S4 ^ S5 ^ S6 + else: # 256 bits + tag = (S0 ^ S1 ^ S2 ^ S3) || (S4 ^ S5 ^ S6 ^ S7) + + return tag + +4. The AEGIS-256 Algorithm + + AEGIS-256 has a 768-bit state, made of six 128-bit blocks {S0, + ...S5}. + + The parameters for this algorithm, whose meaning is defined in + [RFC5116], Section 4 are: + + * K_LEN (key length) is 32 octets (256 bits). + + * P_MAX (maximum length of the plaintext) is 2^61 octets (2^64 + bits). + + * A_MAX (maximum length of the associated data) is 2^61 octets (2^64 + bits). + + * N_MIN (minimum nonce length) = N_MAX (maximum nonce length) = 32 + octets (256 bits). + + * C_MAX (maximum ciphertext length) = P_MAX + tag length = 2^61 + 16 + or 32 octets (2^64 + 128 or 256 bits). + + Distinct associated data inputs, as described in [RFC5116], Section 3 + shall be unambiguously encoded as a single input. It is up to the + application to create a structure in the associated data input if + needed. + +4.1. Authenticated Encryption + + Encrypt(msg, ad, key, nonce) + + The Encrypt function encrypts a message and returns the ciphertext + along with an authentication tag that verifies the authenticity of + the message and associated data, if provided. + + Security: + + * For a given key, the nonce MUST NOT be reused under any + circumstances; doing so allows an attacker to recover the internal + state. + + * The key MUST be randomly chosen from a uniform distribution. + + Inputs: + + * msg: the message to be encrypted (length MUST be less than P_MAX). + + * ad: the associated data to authenticate (length MUST be less than + A_MAX). + + * key: the encryption key. + + * nonce: the public nonce. + + Outputs: + + * ct: the ciphertext. + + * tag: the authentication tag. + + Steps: + + Init(key, nonce) + + ct = {} + + ad_blocks = Split(ZeroPad(ad, 128), 128) + for ai in ad_blocks: + Absorb(ai) + + msg_blocks = Split(ZeroPad(msg, 128), 128) + for xi in msg_blocks: + ct = ct || Enc(xi) + + tag = Finalize(|ad|, |msg|) + ct = Truncate(ct, |msg|) + + return ct and tag + +4.2. Authenticated Decryption + + Decrypt(ct, tag, ad, key, nonce) + + The Decrypt function decrypts a ciphertext, verifies that the + authentication tag is correct, and returns the message on success or + an error if tag verification failed. + + Security: + + * If tag verification fails, the decrypted message and wrong message + authentication tag MUST NOT be given as output. The decrypted + message MUST be overwritten with zeros. + + * The comparison of the input tag with the expected_tag MUST be done + in constant time. + + Inputs: + + * ct: the ciphertext to be decrypted (length MUST be less than + C_MAX). + + * tag: the authentication tag. + + * ad: the associated data to authenticate (length MUST be less than + A_MAX). + + * key: the encryption key. + + * nonce: the public nonce. + + Outputs: + + * Either the decrypted message msg or an error indicating that the + authentication tag is invalid for the given inputs. + + Steps: + + Init(key, nonce) + + msg = {} + + ad_blocks = Split(ZeroPad(ad, 128), 128) + for ai in ad_blocks: + Absorb(ai) + + ct_blocks = Split(ZeroPad(ct, 128), 128) + cn = Tail(ct, |ct| mod 128) + + for ci in ct_blocks: + msg = msg || Dec(ci) + + if cn is not empty: + msg = msg || DecPartial(cn) + + expected_tag = Finalize(|ad|, |msg|) + + if CtEq(tag, expected_tag) is False: + erase msg + return "verification failed" error + else: + return msg + +4.3. The Init Function + + Init(key, nonce) + + The Init function constructs the initial state {S0, ...S5} using the + given key and nonce. + + Inputs: + + * key: the encryption key. + + * nonce: the public nonce. + + Defines: + + * {S0, ...S5}: the initial state. + + Steps: + + k0, k1 = Split(key, 128) + n0, n1 = Split(nonce, 128) + + S0 = k0 ^ n0 + S1 = k1 ^ n1 + S2 = C1 + S3 = C0 + S4 = k0 ^ C0 + S5 = k1 ^ C1 + + Repeat(4, + Update(k0) + Update(k1) + Update(k0 ^ n0) + Update(k1 ^ n1) + ) + +4.4. The Update Function + + Update(M) + + The Update function is the core of the AEGIS-256 algorithm. It + updates the state {S0, ...S5} using a 128-bit value. + + Inputs: + + * msg: the block to be absorbed. + + Modifies: + + * {S0, ...S5}: the state. + + Steps: + + S'0 = AESRound(S5, S0 ^ M) + S'1 = AESRound(S0, S1) + S'2 = AESRound(S1, S2) + S'3 = AESRound(S2, S3) + S'4 = AESRound(S3, S4) + S'5 = AESRound(S4, S5) + + S0 = S'0 + S1 = S'1 + S2 = S'2 + S3 = S'3 + S4 = S'4 + S5 = S'5 + +4.5. The Absorb Function + + Absorb(ai) + + The Absorb function absorbs a 128-bit input block ai into the state + {S0, ...S5}. + + Inputs: + + * ai: the input block. + + Steps: + + Update(ai) + +4.6. The Enc Function + + Enc(xi) + + The Enc function encrypts a 128-bit input block xi using the state + {S0, ...S5}. + + Inputs: + + * xi: the input block. + + Outputs: + + * ci: the encrypted input block. + + Steps: + + z = S1 ^ S4 ^ S5 ^ (S2 & S3) + + Update(xi) + + ci = xi ^ z + + return ci + +4.7. The Dec Function + + Dec(ci) + + The Dec function decrypts a 128-bit input block ci using the state + {S0, ...S5}. + + Inputs: + + * ci: the encrypted input block. + + Outputs: + + * xi: the decrypted block. + + Steps: + + z = S1 ^ S4 ^ S5 ^ (S2 & S3) + + xi = ci ^ z + + Update(xi) + + return xi + +4.8. The DecPartial Function + + DecPartial(cn) + + The DecPartial function decrypts the last ciphertext bits cn using + the state {S0, ...S5} when they do not fill an entire block. + + Inputs: + + * cn: the encrypted input. + + Outputs: + + * xn: the decryption of cn. + + Steps: + + z = S1 ^ S4 ^ S5 ^ (S2 & S3) + + t = ZeroPad(cn, 128) + out = t ^ z + + xn = Truncate(out, |cn|) + + v = ZeroPad(xn, 128) + Update(v) + + return xn + +4.9. The Finalize Function + + Finalize(ad_len_bits, msg_len_bits) + + The Finalize function computes a 128- or 256-bit tag that + authenticates the message and associated data. + + Inputs: + + * ad_len_bits: the length of the associated data in bits. + + * msg_len_bits: the length of the message in bits. + + Outputs: + + * tag: the authentication tag. + + Steps: + + t = S3 ^ (LE64(ad_len_bits) || LE64(msg_len_bits)) + + Repeat(7, Update(t)) + + if tag_length == 16: # 128 bits + tag = S0 ^ S1 ^ S2 ^ S3 ^ S4 ^ S5 + else: # 256 bits + tag = (S0 ^ S1 ^ S2) || (S3 ^ S4 ^ S5) + + return tag + +5. Encoding (ct, tag) Tuples + + Applications MAY keep the ciphertext and the authentication tag in + distinct structures or encode both as a single string. + + In the latter case, the tag MUST immediately follow the ciphertext: + + combined_ct = ct || tag + +6. AEGIS as a Stream Cipher + + All AEGIS variants can also be used as stream ciphers. + + Stream(len, key, nonce) + + The Stream function expands a key and an optional nonce into a + variable-length, secure keystream. + + Inputs: + + * len: the length of the keystream to generate. + + * key: the AEGIS key. + + * nonce: the nonce. If unspecified, it is set to N_MAX zero bytes. + + Outputs: + + * stream: the keystream. + + Steps: + + stream, tag = Encrypt(ZeroPad({}, len), {}, key, nonce) + + return stream + + This is equivalent to encrypting a len all-zero bytes message without + associated data, and discarding the authentication tag. + + Instead of relying on the generic Encrypt function, implementations + can skip the finalization step. + + After initialization, the Update function is called with constant + parameters, allowing further optimizations. + +7. Security Considerations + + AEGIS-256 offers 256-bit message security against plaintext and state + recovery, whereas AEGIS-128L offers 128-bit security. + + An authentication tag may verify under multiple keys, nonces, or + associated data, but AEGIS is assumed to be key committing in the + receiver-binding game, preventing common attacks when used with low- + entropy keys such as passwords. Finding distinct keys and/or nonces + that successfully verify the same (ad, ct, tag) tuple is expected to + require ~2^64 attempts with a 128-bit authentication tag and ~2^128 + attempts with a 256-bit tag. + + However, it is NOT fully committing because the key doesn’t commit to + the associated data. As shown in [IR23], with the ability to also + alter ad, it is possible to efficiently find multiple keys that will + verify the same authenticated ciphertext. + + Under the assumption that the secret key is unknown to the attacker + both AEGIS-128L and AEGIS-256 target 128-bit security against forgery + attacks regardless of the tag size. + + Both algorithms MUST be used in a nonce-respecting setting: for a + given key, a nonce MUST only be used once. Failure to do so would + immediately reveal the bitwise difference between two messages. + + If tag verification fails, the decrypted message and wrong message + authentication tag MUST NOT be given as output. As shown in the + analysis of the (robustness of CAESAR candidates beyond their + guarantees)[VV18], even a partial leak of the plaintext without + verification would facilitate chosen ciphertext attacks. + + Every key MUST be randomly chosen from a uniform distribution. + + The nonce MAY be public or predictable. It can be a counter, the + output of a permutation, or a generator with a long period. + + With AEGIS-128L, random nonces can safely encrypt up to 2^48 messages + using the same key with negligible (~ 2^-33, to align with NIST + guidelines) collision probability. + + With AEGIS-256, random nonces can be used with no practical limits. + + Regardless of the variant, the key and nonce are only required by the + Init function; other functions only depend on the resulting state. + Therefore, implementations can overwrite ephemeral keys with zeros + right after the last Update call of the initialization function. + + The security of AEGIS against timing and physical attacks is limited + by the implementation of the underlying AESRound() function. Failure + to implement AESRound() in a fashion safe against timing and physical + attacks, such as differential power analysis, timing analysis or + fault injection attacks, may lead to leakage of secret key material + or state information. The exact mitigations required for timing and + physical attacks also depend on the threat model in question. + + AEGIS is considered secure against guess-and-determine attacks aimed + at recovering the state from observed ciphertexts. This resilience + extends to quantum adversaries in the Q1 model, wherein quantum + attacks do not confer any practical advantage for decrypting + previously recorded ciphertexts or achieving key recovery. + + Security analyses of AEGIS can be found in Chapter 4 of [AEGIS], in + [M14], in [ENP19], in [LIMS21], in [JLD21], in [STSI23], in [IR23], + and in [BS23]. + +8. IANA Considerations + + IANA has assigned the following identifiers in the AEAD Algorithms + Registry: + + +================+====+ + | Algorithm Name | ID | + +================+====+ + | AEAD_AEGIS128L | 32 | + +----------------+----+ + | AEAD_AEGIS256 | 33 | + +----------------+----+ + + Table 1: AEGIS entries + in the AEAD Algorithms + Registry + + IANA has also assigned the following TLS cipher suites in the TLS + Cipher Suite Registry: + + +=======================+=============+ + | Cipher Suite Name | Value | + +=======================+=============+ + | TLS_AEGIS_256_SHA384 | {0x13,0x06} | + +-----------------------+-------------+ + | TLS_AEGIS_128L_SHA256 | {0x13,0x07} | + +-----------------------+-------------+ + + Table 2: AEGIS entries in the TLS + Cipher Suite Registry + + A 128-bit tag length must be used with these cipher suites. + + IANA is requested to update the references of these entries to refer + to the final version of this document. + +9. QUIC and DTLS 1.3 Header Protection + +9.1. DTLS 1.3 Record Number Encryption + + In DTLS 1.3, record sequence numbers are encrypted as specified in + [RFC9147]. + + For AEGIS-128L and AEGIS-256, the mask is generated using the AEGIS + Stream function with: + + * a 128-bit tag length + + * sn_key, as defined in Section 4.2.3 of [RFC9147] + + * ciphertext[0..16]: the first 16 bytes of the DTLS ciphertext + + * nonce_len: the AEGIS nonce length + + The 5-byte mask is computed as follows: + + mask = Stream(5, sn_key, ZeroPad(ciphertext[0..16], nonce_len)) + +9.2. QUIC Header Protection + + In QUIC, parts of the QUIC packet headers are encrypted as specified + in [RFC9001]. + + For AEGIS-128L and AEGIS-256, the mask is generated using the AEGIS + Encrypt function with: + + * a 128-bit tag length + + * hp_key, as defined in Section 5.4 of [RFC9001] + + * sample: the 16 bytes QUIC ciphertext sample + + * nonce_len: the AEGIS nonce length + + The mask is computed as follows: + + mask = Encrypt("", "", hp_key, ZeroPad(sample, nonce_len)) + +10. References + +10.1. Normative References + + [FIPS-AES] NIST, "Advanced encryption standard (AES)", NIST Federal + Information Processing Standards Publications 197, + DOI 10.6028/NIST.FIPS.197, November 2001, + . + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + . + + [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated + Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, + . + + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, . + +10.2. Informative References + + [AEGIS] Wu, H. and B. Preneel, "AEGIS: A Fast Authenticated + Encryption Algorithm (v1.1)", 15 September 2016, + . + + [BS23] Bonnetain, X. and A. Schrottenloher, "Single-query Quantum + Hidden Shift Attacks", Cryptology ePrint Archive, Paper + 2023/1306, 2023, . + + [ENP19] Eichlseder, M., Nageler, M., and R. Primas, "Analyzing the + Linear Keystream Biases in AEGIS", IACR Transactions on + Symmetric Cryptology, 2019(4), pp. 348–368, + DOI 10.13154/tosc.v2019.i4.348-368, 31 January 2020, + . + + [IR23] Isobe, T. and M. Rahman, "Key Committing Security Analysis + of AEGIS", Cryptology ePrint Archive, Paper 2023/1495, + 2023, . + + [JLD21] Jiao, L., Li, Y., and S. Du, "Guess-and-Determine Attacks + on AEGIS", The Computer Journal, vol 65, 2022(8), pp. + 2221–2230, DOI 10.1093/comjnl/bxab059, 22 May 2021, + . + + [LGR21] Len, J., Grubbs, P., and T. Ristenpart, "Partitioning + Oracle Attacks", 30th USENIX Security Symposium (USENIX + Security 21), pp. 195–212, 2021, + . + + [LIMS21] Liu, F., Isobe, T., Meier, W., and K. Sakamoto, "Weak Keys + in Reduced AEGIS and Tiaoxin", IACR Transactions on + Symmetric Cryptology, 2021(2), pp. 104–139, + DOI 10.46586/tosc.v2021.i2.104-139, 11 June 2021, + . + + [M14] Minaud, B., "Linear Biases in AEGIS Keystream", Selected + Areas in Cryptography. SAC 2014. Lecture Notes in Computer + Science, vol 8781, pp. 290–305, + DOI 10.1007/978-3-319-13051-4_18, 2014, + . + + [STSI23] Shiraya, T., Takeuchi, N., Sakamoto, K., and T. Isobe, + "MILP-based security evaluation for AEGIS/Tiaoxin-346/ + Rocca", IET Information Security, vol 17, 2023(3), pp. + 458-467, DOI 10.1049/ise2.12109, 27 January 2023, + . + + [VV18] Vaudenay, S. and D. Vizár, "Can Caesar Beat Galois?", + Applied Cryptography and Network Security. ACNS 2018. + Lecture Notes in Computer Science, vol 10892, pp. 476–494, + DOI 10.1007/978-3-319-93387-0_25, 2018, + . + +Appendix A. Test Vectors + +A.1. AESRound Test Vector + + in : 000102030405060708090a0b0c0d0e0f + + rk : 101112131415161718191a1b1c1d1e1f + + out : 7a7b4e5638782546a8c0477a3b813f43 + +A.2. AEGIS-128L Test Vectors + +A.2.1. Update Test Vector + + S0 : 9b7e60b24cc873ea894ecc07911049a3 + S1 : 330be08f35300faa2ebf9a7b0d274658 + S2 : 7bbd5bd2b049f7b9b515cf26fbe7756c + S3 : c35a00f55ea86c3886ec5e928f87db18 + S4 : 9ebccafce87cab446396c4334592c91f + S5 : 58d83e31f256371e60fc6bb257114601 + S6 : 1639b56ea322c88568a176585bc915de + S7 : 640818ffb57dc0fbc2e72ae93457e39a + + M0 : 033e6975b94816879e42917650955aa0 + M1 : 033e6975b94816879e42917650955aa0 + + After Update: + S0 : 596ab773e4433ca0127c73f60536769d + S1 : 790394041a3d26ab697bde865014652d + S2 : 38cf49e4b65248acd533041b64dd0611 + S3 : 16d8e58748f437bfff1797f780337cee + S4 : 69761320f7dd738b281cc9f335ac2f5a + S5 : a21746bb193a569e331e1aa985d0d729 + S6 : 09d714e6fcf9177a8ed1cde7e3d259a6 + S7 : 61279ba73167f0ab76f0a11bf203bdff + +A.2.2. Test Vector 1 + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : + + msg : 00000000000000000000000000000000 + + ct : c1c0e58bd913006feba00f4b3cc3594e + + tag128: abe0ece80c24868a226a35d16bdae37a + + tag256: 25835bfbb21632176cf03840687cb968 + cace4617af1bd0f7d064c639a5c79ee4 + +A.2.3. Test Vector 2 + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : + + msg : + + ct : + + tag128: c2b879a67def9d74e6c14f708bbcc9b4 + + tag256: 1360dc9db8ae42455f6e5b6a9d488ea4 + f2184c4e12120249335c4ee84bafe25d + +A.2.4. Test Vector 3 + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : 0001020304050607 + + msg : 000102030405060708090a0b0c0d0e0f + 101112131415161718191a1b1c1d1e1f + + ct : 79d94593d8c2119d7e8fd9b8fc77845c + 5c077a05b2528b6ac54b563aed8efe84 + + tag128: cc6f3372f6aa1bb82388d695c3962d9a + + tag256: 022cb796fe7e0ae1197525ff67e30948 + 4cfbab6528ddef89f17d74ef8ecd82b3 + +A.2.5. Test Vector 4 + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : 0001020304050607 + + msg : 000102030405060708090a0b0c0d + + ct : 79d94593d8c2119d7e8fd9b8fc77 + + tag128: 5c04b3dba849b2701effbe32c7f0fab7 + + tag256: 86f1b80bfb463aba711d15405d094baf + 4a55a15dbfec81a76f35ed0b9c8b04ac + +A.2.6. Test Vector 5 + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : 000102030405060708090a0b0c0d0e0f + 101112131415161718191a1b1c1d1e1f + 20212223242526272829 + + msg : 101112131415161718191a1b1c1d1e1f + 202122232425262728292a2b2c2d2e2f + 3031323334353637 + + ct : b31052ad1cca4e291abcf2df3502e6bd + b1bfd6db36798be3607b1f94d34478aa + 7ede7f7a990fec10 + + tag128: 7542a745733014f9474417b337399507 + + tag256: b91e2947a33da8bee89b6794e647baf0 + fc835ff574aca3fc27c33be0db2aff98 + +A.2.7. Test Vector 6 + + This test MUST return a “verification failed” error. + + key : 10000200000000000000000000000000 + + nonce : 10010000000000000000000000000000 + + ad : 0001020304050607 + + ct : 79d94593d8c2119d7e8fd9b8fc77 + + tag128: 5c04b3dba849b2701effbe32c7f0fab7 + + tag256: 86f1b80bfb463aba711d15405d094baf + 4a55a15dbfec81a76f35ed0b9c8b04ac + +A.2.8. Test Vector 7 + + This test MUST return a “verification failed” error. + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : 0001020304050607 + + ct : 79d94593d8c2119d7e8fd9b8fc78 + + tag128: 5c04b3dba849b2701effbe32c7f0fab7 + + tag256: 86f1b80bfb463aba711d15405d094baf + 4a55a15dbfec81a76f35ed0b9c8b04ac + +A.2.9. Test Vector 8 + + This test MUST return a “verification failed” error. + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : 0001020304050608 + + ct : 79d94593d8c2119d7e8fd9b8fc77 + + tag128: 5c04b3dba849b2701effbe32c7f0fab7 + + tag256: 86f1b80bfb463aba711d15405d094baf + 4a55a15dbfec81a76f35ed0b9c8b04ac + +A.2.10. Test Vector 9 + + This test MUST return a “verification failed” error. + + key : 10010000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + + ad : 0001020304050607 + + ct : 79d94593d8c2119d7e8fd9b8fc77 + + tag128: 6c04b3dba849b2701effbe32c7f0fab8 + + tag256: 86f1b80bfb463aba711d15405d094baf + 4a55a15dbfec81a76f35ed0b9c8b04ad + +A.3. AEGIS-256 Test Vectors + +A.3.1. Update Test Vector + + S0 : 1fa1207ed76c86f2c4bb40e8b395b43e + S1 : b44c375e6c1e1978db64bcd12e9e332f + S2 : 0dab84bfa9f0226432ff630f233d4e5b + S3 : d7ef65c9b93e8ee60c75161407b066e7 + S4 : a760bb3da073fbd92bdc24734b1f56fb + S5 : a828a18d6a964497ac6e7e53c5f55c73 + + M : b165617ed04ab738afb2612c6d18a1ec + + After Update: + S0 : e6bc643bae82dfa3d991b1b323839dcd + S1 : 648578232ba0f2f0a3677f617dc052c3 + S2 : ea788e0e572044a46059212dd007a789 + S3 : 2f1498ae19b80da13fba698f088a8590 + S4 : a54c2ee95e8c2a2c3dae2ec743ae6b86 + S5 : a3240fceb68e32d5d114df1b5363ab67 + +A.3.2. Test Vector 1 + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : + + msg : 00000000000000000000000000000000 + + ct : 754fc3d8c973246dcc6d741412a4b236 + + tag128: 3fe91994768b332ed7f570a19ec5896e + + tag256: 1181a1d18091082bf0266f66297d167d + 2e68b845f61a3b0527d31fc7b7b89f13 + +A.3.3. Test Vector 2 + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : + + msg : + + ct : + + tag128: e3def978a0f054afd1e761d7553afba3 + + tag256: 6a348c930adbd654896e1666aad67de9 + 89ea75ebaa2b82fb588977b1ffec864a + +A.3.4. Test Vector 3 + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : 0001020304050607 + + msg : 000102030405060708090a0b0c0d0e0f + 101112131415161718191a1b1c1d1e1f + + ct : f373079ed84b2709faee373584585d60 + accd191db310ef5d8b11833df9dec711 + + tag128: 8d86f91ee606e9ff26a01b64ccbdd91d + + tag256: b7d28d0c3c0ebd409fd22b4416050307 + 3a547412da0854bfb9723020dab8da1a + +A.3.5. Test Vector 4 + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : 0001020304050607 + + msg : 000102030405060708090a0b0c0d + + ct : f373079ed84b2709faee37358458 + + tag128: c60b9c2d33ceb058f96e6dd03c215652 + + tag256: 8c1cc703c81281bee3f6d9966e14948b + 4a175b2efbdc31e61a98b4465235c2d9 + +A.3.6. Test Vector 5 + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : 000102030405060708090a0b0c0d0e0f + 101112131415161718191a1b1c1d1e1f + 20212223242526272829 + + msg : 101112131415161718191a1b1c1d1e1f + 202122232425262728292a2b2c2d2e2f + 3031323334353637 + + ct : 57754a7d09963e7c787583a2e7b859bb + 24fa1e04d49fd550b2511a358e3bca25 + 2a9b1b8b30cc4a67 + + tag128: ab8a7d53fd0e98d727accca94925e128 + + tag256: a3aca270c006094d71c20e6910b5161c + 0826df233d08919a566ec2c05990f734 + +A.3.7. Test Vector 6 + + This test MUST return a “verification failed” error. + + key : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + ad : 0001020304050607 + + ct : f373079ed84b2709faee37358458 + + tag128: c60b9c2d33ceb058f96e6dd03c215652 + + tag256: 8c1cc703c81281bee3f6d9966e14948b + 4a175b2efbdc31e61a98b4465235c2d9 + +A.3.8. Test Vector 7 + + This test MUST return a “verification failed” error. + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : 0001020304050607 + + ct : f373079ed84b2709faee37358459 + + tag128: c60b9c2d33ceb058f96e6dd03c215652 + + tag256: 8c1cc703c81281bee3f6d9966e14948b + 4a175b2efbdc31e61a98b4465235c2d9 + +A.3.9. Test Vector 8 + + This test MUST return a “verification failed” error. + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : 0001020304050608 + + ct : f373079ed84b2709faee37358458 + + tag128: c60b9c2d33ceb058f96e6dd03c215652 + + tag256: 8c1cc703c81281bee3f6d9966e14948b + 4a175b2efbdc31e61a98b4465235c2d9 + +A.3.10. Test Vector 9 + + This test MUST return a “verification failed” error. + + key : 10010000000000000000000000000000 + 00000000000000000000000000000000 + + nonce : 10000200000000000000000000000000 + 00000000000000000000000000000000 + + ad : 0001020304050607 + + ct : f373079ed84b2709faee37358458 + + tag128: c60b9c2d33ceb058f96e6dd03c215653 + + tag256: 8c1cc703c81281bee3f6d9966e14948b + 4a175b2efbdc31e61a98b4465235c2da + +Acknowledgments + + The AEGIS authenticated encryption algorithm was invented by Hongjun + Wu and Bart Preneel. + + The round function leverages the AES permutation invented by Joan + Daemen and Vincent Rijmen. They also authored the Pelican MAC that + partly motivated the design of the AEGIS MAC. + + We would like to thank the following individuals for their + contributions: + + * Eric Lagergren and Daniel Bleichenbacher for catching a broken + test vector and Daniel Bleichenbacher for many helpful + suggestions. + + * John Preuß Mattsson for his review of the draft, and for + suggesting how AEGIS should be used in the context of DTLS and + QUIC. + + * Bart Mennink and Charlotte Lefevre as well as Takanori Isobe and + Mostafizar Rahman for investigating the commitment security of the + schemes specified in this document. + +Authors' Addresses + + Frank Denis + Fastly Inc. + Email: fde@00f.net + + + Samuel Lucas + Individual Contributor + Email: samuel-lucas6@pm.me diff --git a/quantum-attacks/index.html b/quantum-attacks/index.html new file mode 100644 index 0000000..ff85c0d --- /dev/null +++ b/quantum-attacks/index.html @@ -0,0 +1,46 @@ + + + + cfrg/draft-irtf-cfrg-aegis-aead quantum-attacks preview + + + + +

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