NAME

       EVP_KEM_fetch, EVP_KEM_free, EVP_KEM_up_ref, EVP_KEM_get0_name, EVP_KEM_is_a, EVP_KEM_get0_provider,
       EVP_KEM_do_all_provided, EVP_KEM_names_do_all, EVP_KEM_get0_description, EVP_KEM_gettable_ctx_params,
       EVP_KEM_settable_ctx_params - Functions to manage EVP_KEM algorithm objects

SYNOPSIS

        #include <openssl/evp.h>

        EVP_KEM *EVP_KEM_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                               const char *properties);
        void EVP_KEM_free(EVP_KEM *kem);
        int EVP_KEM_up_ref(EVP_KEM *kem);
        const char *EVP_KEM_get0_name(const EVP_KEM *kem);
        int EVP_KEM_is_a(const EVP_KEM *kem, const char *name);
        OSSL_PROVIDER *EVP_KEM_get0_provider(const EVP_KEM *kem);
        void EVP_KEM_do_all_provided(OSSL_LIB_CTX *libctx,
                                     void (*fn)(EVP_KEM *kem, void *arg), void *arg);
        int EVP_KEM_names_do_all(const EVP_KEM *kem,
                                 void (*fn)(const char *name, void *data), void *data);
        const char *EVP_KEM_get0_description(const EVP_KEM *kem);
        const OSSL_PARAM *EVP_KEM_gettable_ctx_params(const EVP_KEM *kem);
        const OSSL_PARAM *EVP_KEM_settable_ctx_params(const EVP_KEM *kem);

DESCRIPTION

       EVP_KEM_fetch() fetches the implementation for the given algorithm from any provider offering it, within
       the criteria given by the properties and in the scope of the given library context ctx (see
       OSSL_LIB_CTX(3)). The algorithm will be one offering functions for performing asymmetric kem related
       tasks such as key encapsulation and decapsulation.  See "ALGORITHM FETCHING" in crypto(7) for further
       information.

       The returned value must eventually be freed with EVP_KEM_free().

       EVP_KEM_free() decrements the reference count for the EVP_KEM structure.  Typically this structure will
       have been obtained from an earlier call to EVP_KEM_fetch(). If the reference count drops to 0 then the
       structure is freed.

       EVP_KEM_up_ref() increments the reference count for an EVP_KEM structure.

       EVP_KEM_is_a() returns 1 if kem is an implementation of an algorithm that's identifiable with name,
       otherwise 0.

       EVP_KEM_get0_provider() returns the provider that kem was fetched from.

       EVP_KEM_do_all_provided() traverses all EVP_KEMs implemented by all activated providers in the given
       library context libctx, and for each of the implementations, calls the given function fn with the
       implementation method and the given arg as argument.

       EVP_KEM_get0_name() returns the algorithm name from the provided implementation for the given kem. Note
       that the kem may have multiple synonyms associated with it. In this case the first name from the
       algorithm definition is returned. Ownership of the returned string is retained by the kem object and
       should not be freed by the caller.

       EVP_KEM_names_do_all() traverses all names for kem, and calls fn with each name and data.

       EVP_KEM_get0_description() returns a description of the kem, meant for display and human consumption.
       The description is at the discretion of the kem implementation.

       EVP_KEM_gettable_ctx_params() and EVP_KEM_settable_ctx_params() return a constant OSSL_PARAM(3) array
       that describes the names and types of key parameters that can be retrieved or set by a key encapsulation
       algorithm using EVP_PKEY_CTX_get_params(3) and EVP_PKEY_CTX_set_params(3).

RETURN VALUES

       EVP_KEM_fetch() returns a pointer to an EVP_KEM for success or NULL for failure.

       EVP_KEM_up_ref() returns 1 for success or 0 otherwise.

       EVP_KEM_names_do_all() returns 1 if the callback was called for all names. A return value of 0 means that
       the callback was not called for any names.

       EVP_KEM_gettable_ctx_params() and EVP_KEM_settable_ctx_params() return a constant OSSL_PARAM(3) array or
       NULL on error.

SEE ALSO

       "ALGORITHM FETCHING" in crypto(7), OSSL_PROVIDER(3)

HISTORY

       The functions described here were added 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>.