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EVP_SIGNATURE(3)                    OpenSSL                   EVP_SIGNATURE(3)



NAME
       EVP_SIGNATURE, EVP_SIGNATURE_fetch, EVP_SIGNATURE_free,
       EVP_SIGNATURE_up_ref, EVP_SIGNATURE_is_a, EVP_SIGNATURE_get0_provider,
       EVP_SIGNATURE_do_all_provided, EVP_SIGNATURE_names_do_all,
       EVP_SIGNATURE_get0_name, EVP_SIGNATURE_get0_description,
       EVP_SIGNATURE_gettable_ctx_params, EVP_SIGNATURE_settable_ctx_params -
       Functions to manage EVP_SIGNATURE algorithm objects

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/evp.h>

        typedef struct evp_signature_st EVP_SIGNATURE;

        EVP_SIGNATURE *EVP_SIGNATURE_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                                           const char *properties);
        void EVP_SIGNATURE_free(EVP_SIGNATURE *signature);
        int EVP_SIGNATURE_up_ref(EVP_SIGNATURE *signature);
        const char *EVP_SIGNATURE_get0_name(const EVP_SIGNATURE *signature);
        int EVP_SIGNATURE_is_a(const EVP_SIGNATURE *signature, const char *name);
        OSSL_PROVIDER *EVP_SIGNATURE_get0_provider(const EVP_SIGNATURE *signature);
        void EVP_SIGNATURE_do_all_provided(OSSL_LIB_CTX *libctx,
                                           void (*fn)(EVP_SIGNATURE *signature,
                                                      void *arg),
                                           void *arg);
        int EVP_SIGNATURE_names_do_all(const EVP_SIGNATURE *signature,
                                       void (*fn)(const char *name, void *data),
                                       void *data);
        const char *EVP_SIGNATURE_get0_name(const EVP_SIGNATURE *signature);
        const char *EVP_SIGNATURE_get0_description(const EVP_SIGNATURE *signature);
        const OSSL_PARAM *EVP_SIGNATURE_gettable_ctx_params(const EVP_SIGNATURE *sig);
        const OSSL_PARAM *EVP_SIGNATURE_settable_ctx_params(const EVP_SIGNATURE *sig);

DESCRIPTION
       EVP_SIGNATURE_fetch() fetches the implementation for the given
       algorithm from any provider offering it, within the criteria given by
       the properties.  The algorithm will be one offering functions for
       performing signature related tasks such as signing and verifying.  See
       "ALGORITHM FETCHING" in crypto(7) for further information.

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

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

       EVP_SIGNATURE_up_ref() increments the reference count for an
       EVP_SIGNATURE structure.

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

       EVP_SIGNATURE_get0_provider() returns the provider that signature was
       fetched from.

       EVP_SIGNATURE_do_all_provided() traverses all SIGNATURE 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_SIGNATURE_get0_name() returns the algorithm name from the provided
       implementation for the given signature. Note that the signature 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 signature object and should not be freed by
       the caller.

       EVP_SIGNATURE_names_do_all() traverses all names for signature, and
       calls fn with each name and data.

       EVP_SIGNATURE_get0_description() returns a description of the
       signature, meant for display and human consumption.  The description is
       at the discretion of the signature implementation.

       EVP_SIGNATURE_gettable_ctx_params() and
       EVP_SIGNATURE_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 signature algorithm using
       EVP_PKEY_CTX_get_params(3) and EVP_PKEY_CTX_set_params(3).

RETURN VALUES
       EVP_SIGNATURE_fetch() returns a pointer to an EVP_SIGNATURE for success
       or NULL for failure.

       EVP_SIGNATURE_up_ref() returns 1 for success or 0 otherwise.

       EVP_SIGNATURE_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_SIGNATURE_gettable_ctx_params() and
       EVP_SIGNATURE_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 2019-2023 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>.



3.0.12                            2023-10-25                  EVP_SIGNATURE(3)