refactor: rename KeyExpansion to KeyDerivation

so the name matches the one in the spec

BREAKING CHANGE:

Instead of `SframeError.KeyExpansion` use `SframeError.KeyDerivation`

Author: Tobias Waurick

src/crypto/aead.rs

@@ -34,7 +34,7 @@ pub trait AeadDecrypt {
 #[cfg(test)]
 mod test {
 
-    use crate::crypto::key_expansion::KeyExpansion;
+    use crate::crypto::key_derivation::KeyDerivation;
     use crate::header::{FrameCount, KeyId};
     use crate::test_vectors::{get_sframe_test_vector, SframeTest};
     use crate::util::test::assert_bytes_eq;

src/crypto/key_expansion.rs renamed to src/crypto/key_derivation.rs

@@ -4,7 +4,7 @@
 use super::{cipher_suite::CipherSuite, secret::Secret};
 use crate::error::Result;
 
-pub trait KeyExpansion {
+pub trait KeyDerivation {
     fn expand_from<M, K>(cipher_suite: &CipherSuite, key_material: M, key_id: K) -> Result<Secret>
     where
         M: AsRef<[u8]>,
@@ -59,14 +59,14 @@ cfg_if::cfg_if! {
 #[cfg(feature = "openssl")]
 #[cfg(test)]
 mod test {
-    use super::KeyExpansion;
+    use super::KeyDerivation;
     use crate::crypto::cipher_suite::CipherSuite;
     use crate::crypto::secret::Secret;
     use crate::test_vectors::get_sframe_test_vector;
     use crate::{crypto::cipher_suite::CipherSuiteVariant, util::test::assert_bytes_eq};
 
     mod aes_gcm {
-        use crate::crypto::key_expansion::SFRAME_LABEL;
+        use crate::crypto::key_derivation::SFRAME_LABEL;
 
         use super::*;
 

src/crypto/mod.rs

@@ -3,7 +3,7 @@
 
 pub mod aead;
 pub mod cipher_suite;
-pub mod key_expansion;
+pub mod key_derivation;
 pub mod secret;
 
 cfg_if::cfg_if! {

src/crypto/openssl/key_expansion.rs renamed to src/crypto/openssl/key_derivation.rs

@@ -4,16 +4,16 @@
 use crate::{
     crypto::{
         cipher_suite::{CipherSuite, CipherSuiteVariant},
-        key_expansion::{
-            get_hkdf_aead_label, get_hkdf_key_expand_info, get_hkdf_salt_expand_info, KeyExpansion,
-            SFRAME_HDKF_SUB_AUTH_EXPAND_INFO, SFRAME_HKDF_SUB_ENC_EXPAND_INFO,
+        key_derivation::{
+            get_hkdf_aead_label, get_hkdf_key_expand_info, get_hkdf_salt_expand_info,
+            KeyDerivation, SFRAME_HDKF_SUB_AUTH_EXPAND_INFO, SFRAME_HKDF_SUB_ENC_EXPAND_INFO,
         },
         secret::Secret,
     },
     error::{Result, SframeError},
 };
 
-impl KeyExpansion for Secret {
+impl KeyDerivation for Secret {
     fn expand_from<M, K>(cipher_suite: &CipherSuite, key_material: M, key_id: K) -> Result<Secret>
     where
         M: AsRef<[u8]>,
@@ -32,7 +32,7 @@ impl KeyExpansion for Secret {
             Ok(Secret { key, salt, auth })
         };
 
-        try_expand().map_err(|_: openssl::error::ErrorStack| SframeError::KeyExpansion)
+        try_expand().map_err(|_: openssl::error::ErrorStack| SframeError::KeyDerivation)
     }
 }
 

src/crypto/openssl/mod.rs

@@ -2,5 +2,5 @@
 // SPDX-License-Identifier: Apache-2.0 AND MIT
 
 pub mod aead;
-pub mod key_expansion;
+pub mod key_derivation;
 pub mod tag;

src/crypto/ring/aead.rs

@@ -47,7 +47,7 @@ impl From<CipherSuiteVariant> for &'static ring::aead::Algorithm {
 impl CipherSuite {
     fn unbound_encryption_key(&self, secret: &Secret) -> Result<ring::aead::UnboundKey> {
         ring::aead::UnboundKey::new(self.variant.into(), secret.key.as_slice())
-            .map_err(|_| SframeError::KeyExpansion)
+            .map_err(|_| SframeError::KeyDerivation)
     }
 }
 

src/crypto/ring/key_expansion.rs renamed to src/crypto/ring/key_derivation.rs

@@ -4,13 +4,13 @@
 use crate::{
     crypto::{
         cipher_suite::{CipherSuite, CipherSuiteVariant},
-        key_expansion::{get_hkdf_key_expand_info, get_hkdf_salt_expand_info, KeyExpansion},
+        key_derivation::{get_hkdf_key_expand_info, get_hkdf_salt_expand_info, KeyDerivation},
         secret::Secret,
     },
     error::{Result, SframeError},
 };
 
-impl KeyExpansion for Secret {
+impl KeyDerivation for Secret {
     fn expand_from<M, K>(cipher_suite: &CipherSuite, key_material: M, key_id: K) -> Result<Secret>
     where
         M: AsRef<[u8]>,
@@ -63,7 +63,7 @@ fn expand_key(prk: &ring::hkdf::Prk, info: &[u8], key_len: usize) -> Result<Vec<
 
     prk.expand(&[info], OkmKeyLength(key_len))
         .and_then(|okm| okm.fill(sframe_key.as_mut_slice()))
-        .map_err(|_| SframeError::KeyExpansion)?;
+        .map_err(|_| SframeError::KeyDerivation)?;
 
     Ok(sframe_key)
 }

src/crypto/ring/mod.rs

@@ -2,4 +2,4 @@
 // SPDX-License-Identifier: Apache-2.0 AND MIT
 
 pub mod aead;
-pub mod key_expansion;
+pub mod key_derivation;

src/error.rs

@@ -27,7 +27,7 @@ pub enum SframeError {
 
     /// Could not expand encryption key for [`Sender`] or decryption key for [`Receiver`] with HKDF
     #[error("Unable to create unbound encryption key")]
-    KeyExpansion,
+    KeyDerivation,
 
     /// frame validation failed in the [`Receiver`] before decryption
     #[error("{0}")]

src/receiver.rs

@@ -7,7 +7,7 @@ use crate::{
     crypto::{
         aead::AeadDecrypt,
         cipher_suite::{CipherSuite, CipherSuiteVariant},
-        key_expansion::KeyExpansion,
+        key_derivation::KeyDerivation,
         secret::Secret,
     },
     error::{Result, SframeError},

src/sender.rs

@@ -5,7 +5,7 @@ use crate::{
     crypto::{
         aead::AeadEncrypt,
         cipher_suite::{CipherSuite, CipherSuiteVariant},
-        key_expansion::KeyExpansion,
+        key_derivation::KeyDerivation,
         secret::Secret,
     },
     error::{Result, SframeError},