diff options
author | William Joye <wjoye@cfa.harvard.edu> | 2017-05-02 16:06:33 (GMT) |
---|---|---|
committer | William Joye <wjoye@cfa.harvard.edu> | 2017-05-02 16:06:33 (GMT) |
commit | 335ca9eb0d2337314cbbec5eb19f9aeea0eaaca7 (patch) | |
tree | 0a0e8d65ee114cb89f58c3159488dd5523123309 /openssl/doc/crypto/EVP_SignInit.pod | |
parent | a90d8737b83a4a5bb2bf91a9bdf48a3dad4b51fa (diff) | |
download | blt-335ca9eb0d2337314cbbec5eb19f9aeea0eaaca7.zip blt-335ca9eb0d2337314cbbec5eb19f9aeea0eaaca7.tar.gz blt-335ca9eb0d2337314cbbec5eb19f9aeea0eaaca7.tar.bz2 |
initial commit
Diffstat (limited to 'openssl/doc/crypto/EVP_SignInit.pod')
-rw-r--r-- | openssl/doc/crypto/EVP_SignInit.pod | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/openssl/doc/crypto/EVP_SignInit.pod b/openssl/doc/crypto/EVP_SignInit.pod new file mode 100644 index 0000000..c63d6b3 --- /dev/null +++ b/openssl/doc/crypto/EVP_SignInit.pod @@ -0,0 +1,107 @@ +=pod + +=head1 NAME + +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 initialized with +EVP_MD_CTX_init() 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 paramter, 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)|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. + +Due to the link between message digests and public key algorithms the correct +digest algorithm must be used with the correct public key type. A list of +algorithms and associated public key algorithms appears in +L<EVP_DigestInit(3)|EVP_DigestInit(3)>. + +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)|EVP_VerifyInit(3)>, +L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>, +L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, +L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, +L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)> + +=head1 HISTORY + +EVP_SignInit(), EVP_SignUpdate() and EVP_SignFinal() are +available in all versions of SSLeay and OpenSSL. + +EVP_SignInit_ex() was added in OpenSSL 0.9.7. + +=cut |