diff --git a/Cargo.lock b/Cargo.lock
index bbee89f..98ec367 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -368,9 +368,9 @@ dependencies = [
 
 [[package]]
 name = "hybrid-array"
-version = "0.2.0-rc.8"
+version = "0.2.0-rc.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "53668f5da5a41d9eaf4bf7064be46d1ebe6a4e1ceed817f387587b18f2b51047"
+checksum = "4d306b679262030ad8813a82d4915fc04efff97776e4db7f8eb5137039d56400"
 dependencies = [
  "typenum",
  "zeroize",
diff --git a/ssh-cipher/src/chacha20poly1305.rs b/ssh-cipher/src/chacha20poly1305.rs
index 751db88..2a4e8d7 100644
--- a/ssh-cipher/src/chacha20poly1305.rs
+++ b/ssh-cipher/src/chacha20poly1305.rs
@@ -46,7 +46,7 @@ impl ChaCha20Poly1305 {
 
         // TODO(tarcieri): support for using both keys
         let (k_2, _k_1) = key.split_at(KEY_SIZE);
-        let key = Key::from_slice(k_2);
+        let key = Key::try_from(k_2).map_err(|_| Error::KeySize)?;
 
         let nonce = if nonce.is_empty() {
             // For key encryption
@@ -55,7 +55,7 @@ impl ChaCha20Poly1305 {
             Nonce::try_from(nonce).map_err(|_| Error::IvSize)?
         };
 
-        let mut cipher = ChaCha20::new(key, &nonce.into());
+        let mut cipher = ChaCha20::new(&key, &nonce.into());
         let mut poly1305_key = poly1305::Key::default();
         cipher.apply_keystream(&mut poly1305_key);
 
diff --git a/ssh-key/src/signature.rs b/ssh-key/src/signature.rs
index 75a997e..4634562 100644
--- a/ssh-key/src/signature.rs
+++ b/ssh-key/src/signature.rs
@@ -534,19 +534,15 @@ impl TryFrom<&Signature> for p256::ecdsa::Signature {
 }
 #[cfg(feature = "p256")]
 fn p256_signature_from_openssh_bytes(mut signature_bytes: &[u8]) -> Result<p256::ecdsa::Signature> {
-    const FIELD_SIZE: usize = 32;
-
     let reader = &mut signature_bytes;
     let r = Mpint::decode(reader)?;
     let s = Mpint::decode(reader)?;
 
     match (r.as_positive_bytes(), s.as_positive_bytes()) {
-        (Some(r), Some(s)) if r.len() == FIELD_SIZE && s.len() == FIELD_SIZE => {
-            Ok(p256::ecdsa::Signature::from_scalars(
-                *p256::FieldBytes::from_slice(r),
-                *p256::FieldBytes::from_slice(s),
-            )?)
-        }
+        (Some(r), Some(s)) => Ok(p256::ecdsa::Signature::from_scalars(
+            p256::FieldBytes::try_from(r).map_err(|_| Error::Crypto)?,
+            p256::FieldBytes::try_from(s).map_err(|_| Error::Crypto)?,
+        )?),
         _ => Err(Error::Crypto),
     }
 }
@@ -556,8 +552,6 @@ impl TryFrom<&Signature> for p384::ecdsa::Signature {
     type Error = Error;
 
     fn try_from(signature: &Signature) -> Result<p384::ecdsa::Signature> {
-        const FIELD_SIZE: usize = 48;
-
         match signature.algorithm {
             Algorithm::Ecdsa {
                 curve: EcdsaCurve::NistP384,
@@ -567,12 +561,10 @@ impl TryFrom<&Signature> for p384::ecdsa::Signature {
                 let s = Mpint::decode(reader)?;
 
                 match (r.as_positive_bytes(), s.as_positive_bytes()) {
-                    (Some(r), Some(s)) if r.len() == FIELD_SIZE && s.len() == FIELD_SIZE => {
-                        Ok(p384::ecdsa::Signature::from_scalars(
-                            *p384::FieldBytes::from_slice(r),
-                            *p384::FieldBytes::from_slice(s),
-                        )?)
-                    }
+                    (Some(r), Some(s)) => Ok(p384::ecdsa::Signature::from_scalars(
+                        p384::FieldBytes::try_from(r).map_err(|_| Error::Crypto)?,
+                        p384::FieldBytes::try_from(s).map_err(|_| Error::Crypto)?,
+                    )?),
                     _ => Err(Error::Crypto),
                 }
             }
@@ -586,8 +578,6 @@ impl TryFrom<&Signature> for p521::ecdsa::Signature {
     type Error = Error;
 
     fn try_from(signature: &Signature) -> Result<p521::ecdsa::Signature> {
-        const FIELD_SIZE: usize = 66;
-
         match signature.algorithm {
             Algorithm::Ecdsa {
                 curve: EcdsaCurve::NistP521,
@@ -597,12 +587,10 @@ impl TryFrom<&Signature> for p521::ecdsa::Signature {
                 let s = Mpint::decode(reader)?;
 
                 match (r.as_positive_bytes(), s.as_positive_bytes()) {
-                    (Some(r), Some(s)) if r.len() == FIELD_SIZE && s.len() == FIELD_SIZE => {
-                        Ok(p521::ecdsa::Signature::from_scalars(
-                            *p521::FieldBytes::from_slice(r),
-                            *p521::FieldBytes::from_slice(s),
-                        )?)
-                    }
+                    (Some(r), Some(s)) => Ok(p521::ecdsa::Signature::from_scalars(
+                        p521::FieldBytes::try_from(r).map_err(|_| Error::Crypto)?,
+                        p521::FieldBytes::try_from(s).map_err(|_| Error::Crypto)?,
+                    )?),
                     _ => Err(Error::Crypto),
                 }
             }