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Terminology: say "key derivation operation", not "generator"

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Generators are mostly about key derivation (currently: only about key
derivation). "Generator" is not a commonly used term in cryptography.
So favor "derivation" as terminology.

This commit updates the function descriptions.
This commit is contained in:
Gilles Peskine 2019-05-16 17:26:11 +02:00
parent cbe6650394
commit 35675b6b26
3 changed files with 112 additions and 100 deletions
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202
include/psa/crypto.h
View file

@ -2969,33 +2969,33 @@ psa_status_t psa_asymmetric_decrypt(psa_key_handle_t handle,
/**@}*/
/** \defgroup generators Generators
/** \defgroup key_derivation Key derivation and pseudorandom generation
* @{
*/
/** The type of the state data structure for generators.
/** The type of the state data structure for key derivation operations.
*
* Before calling any function on a generator, the application must
* initialize it by any of the following means:
* Before calling any function on a key derivation operation object, the
* application must initialize it by any of the following means:
* - Set the structure to all-bits-zero, for example:
* \code
* psa_key_derivation_operation_t generator;
* memset(&generator, 0, sizeof(generator));
* psa_key_derivation_operation_t operation;
* memset(&operation, 0, sizeof(operation));
* \endcode
* - Initialize the structure to logical zero values, for example:
* \code
* psa_key_derivation_operation_t generator = {0};
* psa_key_derivation_operation_t operation = {0};
* \endcode
* - Initialize the structure to the initializer #PSA_KEY_DERIVATION_OPERATION_INIT,
* for example:
* \code
* psa_key_derivation_operation_t generator = PSA_KEY_DERIVATION_OPERATION_INIT;
* psa_key_derivation_operation_t operation = PSA_KEY_DERIVATION_OPERATION_INIT;
* \endcode
* - Assign the result of the function psa_key_derivation_operation_init()
* to the structure, for example:
* \code
* psa_key_derivation_operation_t generator;
* generator = psa_key_derivation_operation_init();
* psa_key_derivation_operation_t operation;
* operation = psa_key_derivation_operation_init();
* \endcode
*
* This is an implementation-defined \c struct. Applications should not
@ -3006,8 +3006,8 @@ typedef struct psa_key_derivation_s psa_key_derivation_operation_t;
/** \def PSA_KEY_DERIVATION_OPERATION_INIT
*
* This macro returns a suitable initializer for a generator object
* of type #psa_key_derivation_operation_t.
* This macro returns a suitable initializer for a key derivation operation
* object of type #psa_key_derivation_operation_t.
*/
#ifdef __DOXYGEN_ONLY__
/* This is an example definition for documentation purposes.
@ -3016,58 +3016,66 @@ typedef struct psa_key_derivation_s psa_key_derivation_operation_t;
#define PSA_KEY_DERIVATION_OPERATION_INIT {0}
#endif
/** Return an initial value for a generator object.
/** Return an initial value for a key derivation operation object.
*/
static psa_key_derivation_operation_t psa_key_derivation_operation_init(void);
/** Retrieve the current capacity of a generator.
/** Retrieve the current capacity of a key derivation operation.
*
* The capacity of a generator is the maximum number of bytes that it can
* return. Reading *N* bytes from a generator reduces its capacity by *N*.
* The capacity of a key derivation is the maximum number of bytes that it can
* return. When you get *N* bytes of output from a key derivation operation,
* this reduces its capacity by *N*.
*
* \param[in] generator The generator to query.
* \param[out] capacity On success, the capacity of the generator.
* \param[in] operation The operation to query.
* \param[out] capacity On success, the capacity of the operation.
*
* \retval #PSA_SUCCESS
* \retval #PSA_ERROR_BAD_STATE
* \retval #PSA_ERROR_COMMUNICATION_FAILURE
*/
psa_status_t psa_key_derivation_get_capacity(const psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_get_capacity(const psa_key_derivation_operation_t *operation,
size_t *capacity);
/** Set the maximum capacity of a generator.
/** Set the maximum capacity of a key derivation operation.
*
* \param[in,out] generator The generator object to modify.
* \param capacity The new capacity of the generator.
* It must be less or equal to the generator's
* The capacity of a key derivation operation is the maximum number of bytes
* that the key derivation operation can return from this point onwards.
*
* \param[in,out] operation The key derivation operation object to modify.
* \param capacity The new capacity of the operation.
* It must be less or equal to the operation's
* current capacity.
*
* \retval #PSA_SUCCESS
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \p capacity is larger than the generator's current capacity.
* \p capacity is larger than the operation's current capacity.
* In this case, the operation object remains valid and its capacity
* remains unchanged.
* \retval #PSA_ERROR_BAD_STATE
* \retval #PSA_ERROR_COMMUNICATION_FAILURE
*/
psa_status_t psa_key_derivation_set_capacity(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_set_capacity(psa_key_derivation_operation_t *operation,
size_t capacity);
/** Read some data from a generator.
/** Read some data from a key derivation operation.
*
* This function reads and returns a sequence of bytes from a generator.
* The data that is read is discarded from the generator. The generator's
* capacity is decreased by the number of bytes read.
* This function calculates output bytes from a key derivation algorithm and
* return those bytes.
* If you view the key derivation's output as a stream of bytes, this
* function destructively reads the requested number of bytes from the
* stream.
* The operation's capacity decreases by the number of bytes read.
*
* \param[in,out] generator The generator object to read from.
* \param[out] output Buffer where the generator output will be
* written.
* \param[in,out] operation The key derivation operation object to read from.
* \param[out] output Buffer where the output will be written.
* \param output_length Number of bytes to output.
*
* \retval #PSA_SUCCESS
* \retval #PSA_ERROR_INSUFFICIENT_DATA
* There were fewer than \p output_length bytes
* in the generator. Note that in this case, no
* output is written to the output buffer.
* The generator's capacity is set to 0, thus
* The operation's capacity was less than
* \p output_length bytes. Note that in this case,
* no output is written to the output buffer.
* The operation's capacity is set to 0, thus
* subsequent calls to this function will not
* succeed, even with a smaller output buffer.
* \retval #PSA_ERROR_BAD_STATE
@ -3076,15 +3084,21 @@ psa_status_t psa_key_derivation_set_capacity(psa_key_derivation_operation_t *gen
* \retval #PSA_ERROR_HARDWARE_FAILURE
* \retval #PSA_ERROR_TAMPERING_DETECTED
*/
psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *operation,
uint8_t *output,
size_t output_length);
/** Generate a key deterministically from data read from a generator.
/** Derive a key from an ongoing key derivation operation.
*
* This function uses the output of a generator to derive a key.
* How much output it consumes and how the key is derived depends on the
* key type.
* This function calculates output bytes from a key derivation algorithm
* and uses those bytes to generate a key deterministically.
* If you view the key derivation's output as a stream of bytes, this
* function destructively reads as many bytes as required from the
* stream.
* The operation's capacity decreases by the number of bytes read.
*
* How much output is produced and consumed from the operation, and how
* the key is derived, depends on the key type:
*
* - For key types for which the key is an arbitrary sequence of bytes
* of a given size,
@ -3094,7 +3108,7 @@ psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *gen
* if the implementation provides an isolation boundary then
* the key material is not exposed outside the isolation boundary.
* As a consequence, for these key types, this function always consumes
* exactly (\p bits / 8) bytes from the generator.
* exactly (\p bits / 8) bytes from the operation.
* The following key types defined in this specification follow this scheme:
*
* - #PSA_KEY_TYPE_AES;
@ -3120,7 +3134,7 @@ psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *gen
* up to the nearest whole number of bytes. If the resulting byte string
* is acceptable, it becomes the key, otherwise the drawn bytes are discarded.
* This process is repeated until an acceptable byte string is drawn.
* The byte string drawn from the generator is interpreted as specified
* The byte string drawn from the operation is interpreted as specified
* for the output produced by psa_export_key().
* The following key types defined in this specification follow this scheme:
*
@ -3130,7 +3144,7 @@ psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *gen
* successively (for example, for 3-key triple-DES,
* if the first 8 bytes specify a weak key and the next 8 bytes do not,
* discard the first 8 bytes, use the next 8 bytes as the first key,
* and continue reading output from the generator to derive the other
* and continue reading output from the operation to derive the other
* two keys).
* - Finite-field Diffie-Hellman keys (#PSA_KEY_TYPE_DH_KEYPAIR),
* DSA keys (#PSA_KEY_TYPE_DSA_KEYPAIR), and
@ -3151,14 +3165,14 @@ psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *gen
* FIPS 186-4 §B.4.2 for elliptic curve keys.
*
* - For other key types, including #PSA_KEY_TYPE_RSA_KEYPAIR,
* the way in which the generator output is consumed is
* the way in which the operation output is consumed is
* implementation-defined.
*
* In all cases, the data that is read is discarded from the generator.
* The generator's capacity is decreased by the number of bytes read.
* In all cases, the data that is read is discarded from the operation.
* The operation's capacity is decreased by the number of bytes read.
*
* \param[in] attributes The attributes for the new key.
* \param[in,out] generator The generator object to read from.
* \param[in,out] operation The key derivation operation object to read from.
* \param[out] handle On success, a handle to the newly created key.
* \c 0 on failure.
*
@ -3172,7 +3186,7 @@ psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *gen
* \retval #PSA_ERROR_INSUFFICIENT_DATA
* There was not enough data to create the desired key.
* Note that in this case, no output is written to the output buffer.
* The generator's capacity is set to 0, thus subsequent calls to
* The operation's capacity is set to 0, thus subsequent calls to
* this function will not succeed, even with a smaller output buffer.
* \retval #PSA_ERROR_NOT_SUPPORTED
* The key type or key size is not supported, either by the
@ -3189,24 +3203,24 @@ psa_status_t psa_key_derivation_output_bytes(psa_key_derivation_operation_t *gen
* results in this error code.
*/
psa_status_t psa_key_derivation_output_key(const psa_key_attributes_t *attributes,
psa_key_derivation_operation_t *generator,
psa_key_derivation_operation_t *operation,
psa_key_handle_t *handle);
/** Abort a generator.
/** Abort a key derivation operation.
*
* Once a generator has been aborted, its capacity is zero.
* Aborting a generator frees all associated resources except for the
* \c generator structure itself.
* Once a key derivation operation has been aborted, its capacity is zero.
* Aborting an operation frees all associated resources except for the
* \c operation structure itself.
*
* This function may be called at any time as long as the generator
* This function may be called at any time as long as the operation
* object has been initialized to #PSA_KEY_DERIVATION_OPERATION_INIT, to
* psa_key_derivation_operation_init() or a zero value. In particular, it is valid
* to call psa_key_derivation_abort() twice, or to call psa_key_derivation_abort()
* on a generator that has not been set up.
* on an operation that has not been set up.
*
* Once aborted, the generator object may be called.
* Once aborted, the key derivation operation object may be called.
*
* \param[in,out] generator The generator to abort.
* \param[in,out] operation The operation to abort.
*
* \retval #PSA_SUCCESS
* \retval #PSA_ERROR_BAD_STATE
@ -3214,46 +3228,44 @@ psa_status_t psa_key_derivation_output_key(const psa_key_attributes_t *attribute
* \retval #PSA_ERROR_HARDWARE_FAILURE
* \retval #PSA_ERROR_TAMPERING_DETECTED
*/
psa_status_t psa_key_derivation_abort(psa_key_derivation_operation_t *generator);
psa_status_t psa_key_derivation_abort(psa_key_derivation_operation_t *operation);
/** Use the maximum possible capacity for a generator.
/** Use the maximum possible capacity for a key derivation operation.
*
* Use this value as the capacity argument when setting up a generator
* to indicate that the generator should have the maximum possible capacity.
* The value of the maximum possible capacity depends on the generator
* Use this value as the capacity argument when setting up a key derivation
* to indicate that the operation should have the maximum possible capacity.
* The value of the maximum possible capacity depends on the key derivation
* algorithm.
*/
#define PSA_KEY_DERIVATION_UNLIMITED_CAPACITY ((size_t)(-1))
/**@}*/
/** \defgroup derivation Key derivation
* @{
*/
/** Set up a key derivation operation.
*
* A key derivation algorithm takes some inputs and uses them to create
* a byte generator which can be used to produce keys and other
* A key derivation algorithm takes some inputs and uses them to generate
* a byte stream in a deterministic way.
* This byte stream can be used to produce keys and other
* cryptographic material.
*
* To use a generator for key derivation:
* To derive a key:
* - Start with an initialized object of type #psa_key_derivation_operation_t.
* - Call psa_key_derivation_setup() to select the algorithm.
* - Provide the inputs for the key derivation by calling
* psa_key_derivation_input_bytes() or psa_key_derivation_input_key()
* as appropriate. Which inputs are needed, in what order, and whether
* they may be keys and if so of what type depends on the algorithm.
* - Optionally set the generator's maximum capacity with
* - Optionally set the operation's maximum capacity with
* psa_key_derivation_set_capacity(). You may do this before, in the middle of
* or after providing inputs. For some algorithms, this step is mandatory
* because the output depends on the maximum capacity.
* - Generate output with psa_key_derivation_output_bytes() or
* psa_key_derivation_output_key(). Successive calls to these functions
* use successive output bytes from the generator.
* - Clean up the generator object with psa_key_derivation_abort().
* - To derive a key, call psa_key_derivation_output_key().
* To derive a byte string for a different purpose, call
* - psa_key_derivation_output_bytes().
* Successive calls to these functions use successive output bytes
* calculated by the key derivation algorithm.
* - Clean up the key derivation operation object with psa_key_derivation_abort().
*
* \param[in,out] generator The generator object to set up. It must
* \param[in,out] operation The key derivation operation object
* to set up. It must
* have been initialized but not set up yet.
* \param alg The key derivation algorithm to compute
* (\c PSA_ALG_XXX value such that
@ -3271,7 +3283,7 @@ psa_status_t psa_key_derivation_abort(psa_key_derivation_operation_t *generator)
* \retval #PSA_ERROR_TAMPERING_DETECTED
* \retval #PSA_ERROR_BAD_STATE
*/
psa_status_t psa_key_derivation_setup(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_setup(psa_key_derivation_operation_t *operation,
psa_algorithm_t alg);
/** Provide an input for key derivation or key agreement.
@ -3284,8 +3296,8 @@ psa_status_t psa_key_derivation_setup(psa_key_derivation_operation_t *generator,
* using psa_key_derivation_input_key() instead of this function. Refer to
* the documentation of individual step types for information.
*
* \param[in,out] generator The generator object to use. It must
* have been set up with
* \param[in,out] operation The key derivation operation object to use.
* It must have been set up with
* psa_key_derivation_setup() and must not
* have produced any output yet.
* \param step Which step the input data is for.
@ -3295,7 +3307,7 @@ psa_status_t psa_key_derivation_setup(psa_key_derivation_operation_t *generator,
* \retval #PSA_SUCCESS
* Success.
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \c step is not compatible with the generator's algorithm.
* \c step is not compatible with the operation's algorithm.
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \c step does not allow direct inputs.
* \retval #PSA_ERROR_INSUFFICIENT_MEMORY
@ -3303,13 +3315,13 @@ psa_status_t psa_key_derivation_setup(psa_key_derivation_operation_t *generator,
* \retval #PSA_ERROR_HARDWARE_FAILURE
* \retval #PSA_ERROR_TAMPERING_DETECTED
* \retval #PSA_ERROR_BAD_STATE
* The value of \p step is not valid given the state of \p generator.
* The value of \p step is not valid given the state of \p operation.
* \retval #PSA_ERROR_BAD_STATE
* The library has not been previously initialized by psa_crypto_init().
* It is implementation-dependent whether a failure to initialize
* results in this error code.
*/
psa_status_t psa_key_derivation_input_bytes(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_input_bytes(psa_key_derivation_operation_t *operation,
psa_key_derivation_step_t step,
const uint8_t *data,
size_t data_length);
@ -3325,8 +3337,8 @@ psa_status_t psa_key_derivation_input_bytes(psa_key_derivation_operation_t *gene
* passed as direct inputs using psa_key_derivation_input_bytes(). Refer to
* the documentation of individual step types for information.
*
* \param[in,out] generator The generator object to use. It must
* have been set up with
* \param[in,out] operation The key derivation operation object to use.
* It must have been set up with
* psa_key_derivation_setup() and must not
* have produced any output yet.
* \param step Which step the input data is for.
@ -3340,7 +3352,7 @@ psa_status_t psa_key_derivation_input_bytes(psa_key_derivation_operation_t *gene
* \retval #PSA_ERROR_DOES_NOT_EXIST
* \retval #PSA_ERROR_NOT_PERMITTED
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \c step is not compatible with the generator's algorithm.
* \c step is not compatible with the operation's algorithm.
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \c step does not allow key inputs.
* \retval #PSA_ERROR_INSUFFICIENT_MEMORY
@ -3348,13 +3360,13 @@ psa_status_t psa_key_derivation_input_bytes(psa_key_derivation_operation_t *gene
* \retval #PSA_ERROR_HARDWARE_FAILURE
* \retval #PSA_ERROR_TAMPERING_DETECTED
* \retval #PSA_ERROR_BAD_STATE
* The value of \p step is not valid given the state of \p generator.
* The value of \p step is not valid given the state of \p operation.
* \retval #PSA_ERROR_BAD_STATE
* The library has not been previously initialized by psa_crypto_init().
* It is implementation-dependent whether a failure to initialize
* results in this error code.
*/
psa_status_t psa_key_derivation_input_key(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_input_key(psa_key_derivation_operation_t *operation,
psa_key_derivation_step_t step,
psa_key_handle_t handle);
@ -3365,17 +3377,17 @@ psa_status_t psa_key_derivation_input_key(psa_key_derivation_operation_t *genera
* a public key \p peer_key.
* The result of this function is passed as input to a key derivation.
* The output of this key derivation can be extracted by reading from the
* resulting generator to produce keys and other cryptographic material.
* resulting operation to produce keys and other cryptographic material.
*
* \param[in,out] generator The generator object to use. It must
* have been set up with
* \param[in,out] operation The key derivation operation object to use.
* It must have been set up with
* psa_key_derivation_setup() with a
* key agreement and derivation algorithm
* \c alg (\c PSA_ALG_XXX value such that
* #PSA_ALG_IS_KEY_AGREEMENT(\c alg) is true
* and #PSA_ALG_IS_RAW_KEY_AGREEMENT(\c alg)
* is false).
* The generator must be ready for an
* The operation must be ready for an
* input of the type given by \p step.
* \param step Which step the input data is for.
* \param private_key Handle to the private key to use.
@ -3411,7 +3423,7 @@ psa_status_t psa_key_derivation_input_key(psa_key_derivation_operation_t *genera
* \retval #PSA_ERROR_HARDWARE_FAILURE
* \retval #PSA_ERROR_TAMPERING_DETECTED
*/
psa_status_t psa_key_derivation_key_agreement(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation_key_agreement(psa_key_derivation_operation_t *operation,
psa_key_derivation_step_t step,
psa_key_handle_t private_key,
const uint8_t *peer_key,
@ -3428,7 +3440,7 @@ psa_status_t psa_key_derivation_key_agreement(psa_key_derivation_operation_t *ge
* not be used directly as key material. It should instead be passed as
* input to a key derivation algorithm. To chain a key agreement with
* a key derivation, use psa_key_derivation_key_agreement() and other functions from
* the key derivation and generator interface.
* the key derivation interface.
*
* \param alg The key agreement algorithm to compute
* (\c PSA_ALG_XXX value such that

8
include/psa/crypto_extra.h
View file

@ -157,7 +157,7 @@ psa_status_t mbedtls_psa_inject_entropy(const unsigned char *seed,
* - For HKDF (#PSA_ALG_HKDF), \p salt is the salt used in the "extract" step
* and \p label is the info string used in the "expand" step.
*
* \param[in,out] generator The generator object to set up. It must have
* \param[in,out] operation The key derivation object to set up. It must have
* been initialized as per the documentation for
* #psa_key_derivation_operation_t and not yet in use.
* \param handle Handle to the secret key.
@ -169,7 +169,7 @@ psa_status_t mbedtls_psa_inject_entropy(const unsigned char *seed,
* \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.
* operation will be able to provide.
*
* \retval #PSA_SUCCESS
* Success.
@ -190,7 +190,7 @@ psa_status_t mbedtls_psa_inject_entropy(const unsigned char *seed,
* It is implementation-dependent whether a failure to initialize
* results in this error code.
*/
psa_status_t psa_key_derivation(psa_key_derivation_operation_t *generator,
psa_status_t psa_key_derivation(psa_key_derivation_operation_t *operation,
psa_key_handle_t handle,
psa_algorithm_t alg,
const uint8_t *salt,
@ -433,7 +433,7 @@ psa_status_t psa_copy_key_to_handle(psa_key_handle_t source_handle,
psa_status_t psa_generate_derived_key_to_handle(psa_key_handle_t handle,
psa_key_type_t type,
size_t bits,
psa_key_derivation_operation_t *generator);
psa_key_derivation_operation_t *operation);
psa_status_t psa_generate_random_key_to_handle(psa_key_handle_t handle,
psa_key_type_t type,

2
include/psa/crypto_struct.h
View file

@ -195,7 +195,7 @@ typedef struct
typedef struct psa_tls12_prf_key_derivation_s
{
/* The TLS 1.2 PRF uses the key for each HMAC iteration,
* hence we must store it for the lifetime of the generator.
* hence we must store it for the lifetime of the operation.
* This is different from HKDF, where the key is only used
* in the extraction phase, but not during expansion. */
unsigned char *key;