From 1e207400a33792cd186e733b11b07afd5f3f1bc4 Mon Sep 17 00:00:00 2001
From: n1ckl0s <25745329+n1ckl0sk0rtge@users.noreply.github.com>
Date: Fri, 18 Mar 2022 20:28:26 +0100
Subject: [PATCH] add check for minimum key size, add negative test

---
 build/classes/java/test/PseudonymTest.class   | Bin 2526 -> 2847 bytes
 .../previous-compilation-data.bin             | Bin 907 -> 907 bytes
 .../ibm/unlinkablepseudonyms/Pseudonym.java   |   7 +++++--
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/build/classes/java/test/PseudonymTest.class b/build/classes/java/test/PseudonymTest.class
index b094634d6281aee25562a9c788214eec3d534d06..d1fd7be35069757dceed9a51307ed64c98e4f5f8 100644
GIT binary patch
delta 975
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c8PSWr&iC|U+A6vU$7z=LwE13rvrVMl0ZdnqR{#J2

delta 642
zcmXYvOH&h35QV>)WVp$2p~?iK0fQP;9vUKw-~*$GK_$L5D!xOABuGM(h$w2Z@CQJR
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diff --git a/build/tmp/compileTestJava/previous-compilation-data.bin b/build/tmp/compileTestJava/previous-compilation-data.bin
index 0e9e8330254936c198778a6885e91453d396010a..82afd1c7e6be6ba62910781ffc62320ed3acb4e6 100644
GIT binary patch
delta 70
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cTLGUCzL8fXg#=LBdFB4*)*gW-vkC%%0q>(7=l}o!

delta 70
zcmV-M0J;B*2a5-g77)&_Z%J~w1OH6E99J$=)hMwhB>@m@KytW*zo>6iReryYfpl7v
cTLGUCMwR@j&XMD}3$~<(yd+e~vkC%%0S+J@djJ3c

diff --git a/src/main/java/com/ibm/unlinkablepseudonyms/Pseudonym.java b/src/main/java/com/ibm/unlinkablepseudonyms/Pseudonym.java
index aaec1c4..a540498 100644
--- a/src/main/java/com/ibm/unlinkablepseudonyms/Pseudonym.java
+++ b/src/main/java/com/ibm/unlinkablepseudonyms/Pseudonym.java
@@ -1,7 +1,6 @@
 package com.ibm.unlinkablepseudonyms;
 
 import org.apache.commons.codec.digest.DigestUtils;
-
 import java.math.BigInteger;
 import java.security.interfaces.RSAPrivateCrtKey;
 import java.security.interfaces.RSAPublicKey;
@@ -23,7 +22,11 @@ public static byte[] convert(
             byte[] cipher,
             PRFSecretExponent currentSecretExponent,
             PRFSecretExponent targetSecretExponent,
-            RSAPrivateCrtKey privateKey) {
+            RSAPrivateCrtKey privateKey) throws Exception {
+
+        if (privateKey.getModulus().bitLength() <= 256) {
+            throw new Exception("key size to small");
+        }
 
         BigInteger phi = privateKey.getPrimeP().subtract(BigInteger.ONE).multiply(privateKey.getPrimeQ().subtract(BigInteger.ONE));
         BigInteger value = (new BigInteger(cipher)).modPow(targetSecretExponent.asBigInt(), privateKey.getModulus());