Improve comments on key formats
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/3rdparty/p256-m/p256-m_driver_entrypoints.c b/3rdparty/p256-m/p256-m_driver_entrypoints.c
index b75c06c..bcbb651 100644
--- a/3rdparty/p256-m/p256-m_driver_entrypoints.c
+++ b/3rdparty/p256-m/p256-m_driver_entrypoints.c
@@ -38,7 +38,7 @@
* total of 65 bytes.
*
* p256-m's internal format for private keys matches PSA. Its format for public
- * keys is only 64 bytes; the same as PSA but without the leading byte (0x04).
+ * keys is only 64 bytes: the same as PSA but without the leading byte (0x04).
* Hence, when passing public keys from PSA to p256-m, the leading byte is
* removed.
*
@@ -89,6 +89,7 @@
if (data_length != PSA_PUBKEY_SIZE) {
return *bits == 0 ? PSA_ERROR_NOT_SUPPORTED : PSA_ERROR_INVALID_ARGUMENT;
}
+ /* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
if (p256_validate_pubkey(data + 1) != P256_SUCCESS) {
return PSA_ERROR_INVALID_ARGUMENT;
}
@@ -136,7 +137,7 @@
return PSA_ERROR_BUFFER_TOO_SMALL;
}
- /* Output public key in the PSA export format */
+ /* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
data[0] = PSA_PUBKEY_HEADER_BYTE;
int ret = p256_public_from_private(data + 1, key_buffer);
if (ret == P256_SUCCESS) {
@@ -201,10 +202,9 @@
return PSA_ERROR_BUFFER_TOO_SMALL;
}
- /* We add 1 to peer_key pointer to omit the leading byte of the public key
- * representation (0x04). See information about PSA key formats at the top
- * of the file. */
- int ret = p256_ecdh_shared_secret(shared_secret, key_buffer, peer_key + 1);
+ /* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
+ const uint8_t peer_key_p256m = peer_key + 1;
+ int ret = p256_ecdh_shared_secret(shared_secret, key_buffer, peer_key_p256m);
if (ret == P256_SUCCESS) {
*shared_secret_length = SHARED_SECRET_SIZE;
}
@@ -263,11 +263,9 @@
return PSA_ERROR_INVALID_SIGNATURE;
}
- /* We add 1 to public_key_buffer pointer to omit the leading byte of the
- * public key representation (0x04). See information about PSA key formats
- * at the top of the file. */
- const uint8_t *public_key_buffer = key_buffer + 1;
- int ret = p256_ecdsa_verify(signature, public_key_buffer, hash, hash_length);
+ /* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
+ const uint8_t *public_key_p256m = key_buffer + 1;
+ int ret = p256_ecdsa_verify(signature, public_key_p256m, hash, hash_length);
return p256_to_psa_error(ret);
}