bionic (3) EVP_PKEY_security_bits.3ssl.gz

Provided by: libssl-doc_1.1.1-1ubuntu2.1~18.04.23_all bug

NAME
       EVP_PKEY_size, EVP_SignInit, EVP_SignInit_ex, EVP_SignUpdate, EVP_SignFinal, EVP_PKEY_security_bits - EVP
       signing functions


SYNOPSIS
        #include <openssl/evp.h>

        int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
        int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
        int EVP_SignFinal(EVP_MD_CTX *ctx, unsigned char *sig, unsigned int *s, EVP_PKEY *pkey);

        void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type);

        int EVP_PKEY_size(EVP_PKEY *pkey);
        int EVP_PKEY_security_bits(const EVP_PKEY *pkey);


DESCRIPTION
       The EVP signature routines are a high level interface to digital signatures.

       EVP_SignInit_ex() sets up signing context ctx to use digest type from ENGINE impl. ctx must be created
       with EVP_MD_CTX_new() before calling this function.

       EVP_SignUpdate() hashes cnt bytes of data at d into the signature context ctx. This function can be
       called several times on the same ctx to include additional data.

       EVP_SignFinal() signs the data in ctx using the private key pkey and places the signature in sig. sig
       must be at least EVP_PKEY_size(pkey) bytes in size. s is an OUT parameter, and not used as an IN
       parameter.  The number of bytes of data written (i.e. the length of the signature) will be written to the
       integer at s, at most EVP_PKEY_size(pkey) bytes will be written.

       EVP_SignInit() initializes a signing context ctx to use the default implementation of digest type.

       EVP_PKEY_size() returns the maximum size of a signature in bytes. The actual signature returned by
       EVP_SignFinal() may be smaller.

       EVP_PKEY_security_bits() returns the number of security bits of the given pkey, bits of security is
       defined in NIST SP800-57.


RETURN VALUES
       EVP_SignInit_ex(), EVP_SignUpdate() and EVP_SignFinal() return 1 for success and 0 for failure.

       EVP_PKEY_size() returns the maximum size of a signature in bytes.

       The error codes can be obtained by ERR_get_error(3).

       EVP_PKEY_security_bits() returns the number of security bits.


NOTES
       The EVP interface to digital signatures should almost always be used in preference to the low level
       interfaces. This is because the code then becomes transparent to the algorithm used and much more
       flexible.

       When signing with DSA private keys the random number generator must be seeded or the operation will fail.
       The random number generator does not need to be seeded for RSA signatures.

       The call to EVP_SignFinal() internally finalizes a copy of the digest context.  This means that calls to
       EVP_SignUpdate() and EVP_SignFinal() can be called later to digest and sign additional data.

       Since only a copy of the digest context is ever finalized the context must be cleaned up after use by
       calling EVP_MD_CTX_free() or a memory leak will occur.


BUGS
       Older versions of this documentation wrongly stated that calls to EVP_SignUpdate() could not be made
       after calling EVP_SignFinal().

       Since the private key is passed in the call to EVP_SignFinal() any error relating to the private key (for
       example an unsuitable key and digest combination) will not be indicated until after potentially large
       amounts of data have been passed through EVP_SignUpdate().

       It is not possible to change the signing parameters using these function.

       The previous two bugs are fixed in the newer EVP_SignDigest*() function.


SEE ALSO
       EVP_VerifyInit(3), EVP_DigestInit(3), evp(7), HMAC(3), MD2(3), MD5(3), MDC2(3), RIPEMD160(3), SHA1(3),
       dgst(1)


       Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.