Add framework for simple key derivation
New key type PSA_KEY_TYPE_DERIVE. New usage flag PSA_KEY_USAGE_DERIVE.
New function psa_key_derivation.
No key derivation algorithm is implemented yet. The code may not
compile with -Wunused.
Write some unit test code for psa_key_derivation. Most of it cannot be
used yet due to the lack of a key derivation algorithm.
diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 4dbbded..9165463 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -366,6 +366,13 @@
* \c alg is the HMAC algorithm or the underlying hash algorithm. */
#define PSA_KEY_TYPE_HMAC ((psa_key_type_t)0x02000001)
+/** A secret for key derivation.
+ *
+ * The key policy determines which key derivation algorithm the key
+ * can be used for.
+ */
+#define PSA_KEY_TYPE_DERIVE ((psa_key_type_t)0x02000101)
+
/** Key for an cipher, AEAD or MAC algorithm based on the AES block cipher.
*
* The size of the key can be 16 bytes (AES-128), 24 bytes (AES-192) or
@@ -1194,6 +1201,10 @@
*/
#define PSA_KEY_USAGE_VERIFY ((psa_key_usage_t)0x00000800)
+/** Whether the key may be used to derive other keys.
+ */
+#define PSA_KEY_USAGE_DERIVE ((psa_key_usage_t)0x00001000)
+
/** The type of the key policy data structure.
*
* This is an implementation-defined \c struct. Applications should not
@@ -2615,6 +2626,57 @@
/**@}*/
+/** \defgroup derivation Key derivation
+ * @{
+ */
+
+/** Set up a key derivation operation.
+ *
+ * A key derivation algorithm takes three inputs: a secret input \p key and
+ * two non-secret inputs \p label and p salt.
+ * The result of this function is a byte generator which can
+ * be used to produce keys and other cryptographic material.
+ *
+ * The role of \p label and \p salt is as follows:
+ *
+ * \param[in,out] generator The generator object to set up. It must
+ * have been initialized to .
+ * \param key Slot containing the secret key to use.
+ * \param alg The key derivation algorithm to compute
+ * (\c PSA_ALG_XXX value such that
+ * #PSA_ALG_IS_KEY_DERIVATION(\p alg) is true).
+ * \param[in] salt Salt to use.
+ * \param salt_length Size of the \p salt buffer in bytes.
+ * \param[in] label Label to use.
+ * \param label_length Size of the \p label buffer in bytes.
+ * \param capacity The maximum number of bytes that the
+ * generator will be able to provide.
+ *
+ * \retval #PSA_SUCCESS
+ * Success.
+ * \retval #PSA_ERROR_EMPTY_SLOT
+ * \retval #PSA_ERROR_NOT_PERMITTED
+ * \retval #PSA_ERROR_INVALID_ARGUMENT
+ * \c key is not compatible with \c alg,
+ * or \p capacity is too large for the specified algorithm and key.
+ * \retval #PSA_ERROR_NOT_SUPPORTED
+ * \c alg is not supported or is not a key derivation algorithm.
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
+ * \retval #PSA_ERROR_COMMUNICATION_FAILURE
+ * \retval #PSA_ERROR_HARDWARE_FAILURE
+ * \retval #PSA_ERROR_TAMPERING_DETECTED
+ */
+psa_status_t psa_key_derivation(psa_crypto_generator_t *generator,
+ psa_key_type_t key,
+ psa_algorithm_t alg,
+ const uint8_t *salt,
+ size_t salt_length,
+ const uint8_t *label,
+ size_t label_length,
+ size_t capacity);
+
+/**@}*/
+
/** \defgroup generation Key generation
* @{
*/