Updated: 2022/Sep/29
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PROVIDER-KEM(7) OpenSSL PROVIDER-KEM(7)
NAME
provider-kem - The kem library <-> provider functions
LIBRARY
libcrypto, -lcrypto
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 char *name,
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, const char *name);
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_encapsulate OSSL_FUNC_KEM_ENCAPSULATE
OSSL_FUNC_kem_decapsulate_init OSSL_FUNC_KEM_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_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 so
must OSSL_FUNC_kem_settable_ctx_params.
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_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_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.
COPYRIGHT
Copyright 2020-2021 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>.
3.0.12 2023-05-07 PROVIDER-KEM(7)