psa: Expand documentation for psa_key_agreement()

Document `peer_key` parameter requirements, including an explanation of
how the peer key is used and an example for EC keys.
This commit is contained in:
Jaeden Amero 2019-01-14 16:56:20 +00:00
parent 08ad32721c
commit 8afbff82dd

View File

@ -2136,17 +2136,24 @@ psa_status_t psa_key_derivation(psa_crypto_generator_t *generator,
* The resulting generator always has the maximum capacity permitted by
* the algorithm.
*
* \param[in,out] generator The generator object to set up. It must have
* been initialized as per the documentation for
* \param[in,out] generator The generator object to set up. It must have been
* initialized as per the documentation for
* #psa_crypto_generator_t and not yet in use.
* \param private_key Handle to the private key to use.
* \param[in] peer_key Public key of the peer. It must be
* in the same format that psa_import_key()
* accepts. The standard formats for public
* keys are documented in the documentation
* of psa_export_public_key(). For EC keys, it
* must also be of the same group as the private
* key.
* \param[in] peer_key Public key of the peer. The peer key must be in the
* same format that psa_import_key() accepts for the
* public key type corresponding to the type of
* private_key. That is, this function performs the
* equivalent of
* `psa_import_key(internal_public_key_handle,
* PSA_KEY_TYPE_PUBLIC_KEY_OF_KEYPAIR(private_key_type),
* peer_key, peer_key_length)` where
* `private_key_type` is the type of `private_key`.
* For example, for EC keys, this means that peer_key
* is interpreted as a point on the curve that the
* private key is on. The standard formats for public
* keys are documented in the documentation of
* psa_export_public_key().
* \param peer_key_length Size of \p peer_key in bytes.
* \param alg The key agreement algorithm to compute
* (\c PSA_ALG_XXX value such that