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Diffstat (limited to 'openssl-1.1.0h/doc/crypto/EVP_SignInit.pod')
-rw-r--r-- | openssl-1.1.0h/doc/crypto/EVP_SignInit.pod | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/openssl-1.1.0h/doc/crypto/EVP_SignInit.pod b/openssl-1.1.0h/doc/crypto/EVP_SignInit.pod new file mode 100644 index 0000000..21eb868 --- /dev/null +++ b/openssl-1.1.0h/doc/crypto/EVP_SignInit.pod @@ -0,0 +1,105 @@ +=pod + +=head1 NAME + +EVP_PKEY_size, +EVP_SignInit, EVP_SignInit_ex, EVP_SignUpdate, EVP_SignFinal - EVP signing +functions + +=head1 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); + +=head1 DESCRIPTION + +The EVP signature routines are a high level interface to digital +signatures. + +EVP_SignInit_ex() sets up signing context B<ctx> to use digest +B<type> from ENGINE B<impl>. B<ctx> must be created with +EVP_MD_CTX_new() before calling this function. + +EVP_SignUpdate() hashes B<cnt> bytes of data at B<d> into the +signature context B<ctx>. This function can be called several times on the +same B<ctx> to include additional data. + +EVP_SignFinal() signs the data in B<ctx> using the private key B<pkey> and +places the signature in B<sig>. B<sig> must be at least EVP_PKEY_size(pkey) +bytes in size. B<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 B<s>, at most EVP_PKEY_size(pkey) bytes +will be written. + +EVP_SignInit() initializes a signing context B<ctx> to use the default +implementation of digest B<type>. + +EVP_PKEY_size() returns the maximum size of a signature in bytes. The actual +signature returned by EVP_SignFinal() may be smaller. + +=head1 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 L<ERR_get_error(3)>. + +=head1 NOTES + +The B<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_cleanup() or a memory leak +will occur. + +=head1 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. + +=head1 SEE ALSO + +L<EVP_VerifyInit(3)>, +L<EVP_DigestInit(3)>, +L<evp(7)>, L<HMAC(3)>, L<MD2(3)>, +L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>, +L<SHA1(3)>, L<dgst(1)> + +=head1 COPYRIGHT + +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 +L<https://www.openssl.org/source/license.html>. + +=cut |