Provided by: openssl_3.3.1-2ubuntu2_amd64 
NAME
provider-kem - The kem library <-> provider functions
SYNOPSIS
#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
/*
* None of these are actual functions, but are displayed like this for
* the function signatures for functions that are offered as function
* pointers in OSSL_DISPATCH arrays.
*/
/* Context management */
void *OSSL_FUNC_kem_newctx(void *provctx);
void OSSL_FUNC_kem_freectx(void *ctx);
void *OSSL_FUNC_kem_dupctx(void *ctx);
/* Encapsulation */
int OSSL_FUNC_kem_encapsulate_init(void *ctx, void *provkey,
const OSSL_PARAM params[]);
int OSSL_FUNC_kem_auth_encapsulate_init(void *ctx, void *provkey,
void *provauthkey,
const OSSL_PARAM params[]);
int OSSL_FUNC_kem_encapsulate(void *ctx, unsigned char *out, size_t *outlen,
unsigned char *secret, size_t *secretlen);
/* Decapsulation */
int OSSL_FUNC_kem_decapsulate_init(void *ctx, void *provkey);
int OSSL_FUNC_kem_auth_decapsulate_init(void *ctx, void *provkey,
void *provauthkey,
const OSSL_PARAM params[]);
int OSSL_FUNC_kem_decapsulate(void *ctx, unsigned char *out, size_t *outlen,
const unsigned char *in, size_t inlen);
/* KEM parameters */
int OSSL_FUNC_kem_get_ctx_params(void *ctx, OSSL_PARAM params[]);
const OSSL_PARAM *OSSL_FUNC_kem_gettable_ctx_params(void *ctx, void *provctx);
int OSSL_FUNC_kem_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
const OSSL_PARAM *OSSL_FUNC_kem_settable_ctx_params(void *ctx, void *provctx);
DESCRIPTION
This documentation is primarily aimed at provider authors. See provider(7) for further
information.
The asymmetric kem (OSSL_OP_KEM) operation enables providers to implement asymmetric kem
algorithms and make them available to applications via the API functions
EVP_PKEY_encapsulate(3), EVP_PKEY_decapsulate(3) and other related functions.
All "functions" mentioned here are passed as function pointers between libcrypto and the
provider in OSSL_DISPATCH(3) arrays via OSSL_ALGORITHM(3) arrays that are returned by the
provider's provider_query_operation() function (see "Provider Functions" in
provider-base(7)).
All these "functions" have a corresponding function type definition named
OSSL_FUNC_{name}_fn, and a helper function to retrieve the function pointer from an
OSSL_DISPATCH(3) element named OSSL_FUNC_{name}. For example, the "function"
OSSL_FUNC_kem_newctx() has these:
typedef void *(OSSL_FUNC_kem_newctx_fn)(void *provctx);
static ossl_inline OSSL_FUNC_kem_newctx_fn
OSSL_FUNC_kem_newctx(const OSSL_DISPATCH *opf);
OSSL_DISPATCH(3) arrays are indexed by numbers that are provided as macros in
openssl-core_dispatch.h(7), as follows:
OSSL_FUNC_kem_newctx OSSL_FUNC_KEM_NEWCTX
OSSL_FUNC_kem_freectx OSSL_FUNC_KEM_FREECTX
OSSL_FUNC_kem_dupctx OSSL_FUNC_KEM_DUPCTX
OSSL_FUNC_kem_encapsulate_init OSSL_FUNC_KEM_ENCAPSULATE_INIT
OSSL_FUNC_kem_auth_encapsulate_init OSSL_FUNC_KEM_AUTH_ENCAPSULATE_INIT
OSSL_FUNC_kem_encapsulate OSSL_FUNC_KEM_ENCAPSULATE
OSSL_FUNC_kem_decapsulate_init OSSL_FUNC_KEM_DECAPSULATE_INIT
OSSL_FUNC_kem_auth_decapsulate_init OSSL_FUNC_KEM_AUTH_DECAPSULATE_INIT
OSSL_FUNC_kem_decapsulate OSSL_FUNC_KEM_DECAPSULATE
OSSL_FUNC_kem_get_ctx_params OSSL_FUNC_KEM_GET_CTX_PARAMS
OSSL_FUNC_kem_gettable_ctx_params OSSL_FUNC_KEM_GETTABLE_CTX_PARAMS
OSSL_FUNC_kem_set_ctx_params OSSL_FUNC_KEM_SET_CTX_PARAMS
OSSL_FUNC_kem_settable_ctx_params OSSL_FUNC_KEM_SETTABLE_CTX_PARAMS
An asymmetric kem algorithm implementation may not implement all of these functions. In
order to be a consistent set of functions a provider must implement OSSL_FUNC_kem_newctx
and OSSL_FUNC_kem_freectx. It must also implement both of OSSL_FUNC_kem_encapsulate_init
and OSSL_FUNC_kem_encapsulate, or both of OSSL_FUNC_kem_decapsulate_init and
OSSL_FUNC_kem_decapsulate. OSSL_FUNC_kem_auth_encapsulate_init is optional but if it is
present then so must OSSL_FUNC_kem_auth_decapsulate_init. OSSL_FUNC_kem_get_ctx_params is
optional but if it is present then so must OSSL_FUNC_kem_gettable_ctx_params. Similarly,
OSSL_FUNC_kem_set_ctx_params is optional but if it is present then
OSSL_FUNC_kem_settable_ctx_params must also be present.
An asymmetric kem algorithm must also implement some mechanism for generating, loading or
importing keys via the key management (OSSL_OP_KEYMGMT) operation. See
provider-keymgmt(7) for further details.
Context Management Functions
OSSL_FUNC_kem_newctx() should create and return a pointer to a provider side structure for
holding context information during an asymmetric kem operation. A pointer to this context
will be passed back in a number of the other asymmetric kem operation function calls. The
parameter provctx is the provider context generated during provider initialisation (see
provider(7)).
OSSL_FUNC_kem_freectx() is passed a pointer to the provider side asymmetric kem context in
the ctx parameter. This function should free any resources associated with that context.
OSSL_FUNC_kem_dupctx() should duplicate the provider side asymmetric kem context in the
ctx parameter and return the duplicate copy.
Asymmetric Key Encapsulation Functions
OSSL_FUNC_kem_encapsulate_init() initialises a context for an asymmetric encapsulation
given a provider side asymmetric kem context in the ctx parameter, a pointer to a provider
key object in the provkey parameter and the name of the algorithm. The params, if not
NULL, should be set on the context in a manner similar to using
OSSL_FUNC_kem_set_ctx_params(). The key object should have been previously generated,
loaded or imported into the provider using the key management (OSSL_OP_KEYMGMT) operation
(see provider-keymgmt(7)>.
OSSL_FUNC_kem_auth_encapsulate_init() is similar to OSSL_FUNC_kem_encapsulate_init(), but
also passes an additional authentication key provauthkey which cannot be NULL.
OSSL_FUNC_kem_encapsulate() performs the actual encapsulation itself. A previously
initialised asymmetric kem context is passed in the ctx parameter. Unless out is NULL,
the data to be encapsulated is internally generated, and returned into the buffer pointed
to by the secret parameter and the encapsulated data should also be written to the
location pointed to by the out parameter. The length of the encapsulated data should be
written to *outlen and the length of the generated secret should be written to *secretlen.
If out is NULL then the maximum length of the encapsulated data should be written to
*outlen, and the maximum length of the generated secret should be written to *secretlen.
Decapsulation Functions
OSSL_FUNC_kem_decapsulate_init() initialises a context for an asymmetric decapsulation
given a provider side asymmetric kem context in the ctx parameter, a pointer to a provider
key object in the provkey parameter, and a name of the algorithm. The key object should
have been previously generated, loaded or imported into the provider using the key
management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
OSSL_FUNC_kem_auth_decapsulate_init() is similar to OSSL_FUNC_kem_decapsulate_init(), but
also passes an additional authentication key provauthkey which cannot be NULL.
OSSL_FUNC_kem_decapsulate() performs the actual decapsulation itself. A previously
initialised asymmetric kem context is passed in the ctx parameter. The data to be
decapsulated is pointed to by the in parameter which is inlen bytes long. Unless out is
NULL, the decapsulated data should be written to the location pointed to by the out
parameter. The length of the decapsulated data should be written to *outlen. If out is
NULL then the maximum length of the decapsulated data should be written to *outlen.
Asymmetric Key Encapsulation Parameters
See OSSL_PARAM(3) for further details on the parameters structure used by the
OSSL_FUNC_kem_get_ctx_params() and OSSL_FUNC_kem_set_ctx_params() functions.
OSSL_FUNC_kem_get_ctx_params() gets asymmetric kem parameters associated with the given
provider side asymmetric kem context ctx and stores them in params. Passing NULL for
params should return true.
OSSL_FUNC_kem_set_ctx_params() sets the asymmetric kem parameters associated with the
given provider side asymmetric kem context ctx to params. Any parameter settings are
additional to any that were previously set. Passing NULL for params should return true.
No parameters are currently recognised by built-in asymmetric kem algorithms.
OSSL_FUNC_kem_gettable_ctx_params() and OSSL_FUNC_kem_settable_ctx_params() get a constant
OSSL_PARAM(3) array that describes the gettable and settable parameters, i.e. parameters
that can be used with OSSL_FUNC_kem_get_ctx_params() and OSSL_FUNC_kem_set_ctx_params()
respectively.
RETURN VALUES
OSSL_FUNC_kem_newctx() and OSSL_FUNC_kem_dupctx() should return the newly created provider
side asymmetric kem context, or NULL on failure.
All other functions should return 1 for success or 0 on error.
SEE ALSO
provider(7)
HISTORY
The provider KEM interface was introduced in OpenSSL 3.0.
OSSL_FUNC_kem_auth_encapsulate_init() and OSSL_FUNC_kem_auth_decapsulate_init() were added
in OpenSSL 3.2.
COPYRIGHT
Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use this file except
in compliance with the License. You can obtain a copy in the file LICENSE in the source
distribution or at <https://www.openssl.org/source/license.html>.