EVPSignInit(3) OpenSSL EVPSignInit(3)

NAME
       EVPSignInit, EVPSignUpdate, EVPSignFinal - EVP signing functions

SYNOPSIS
        #include 

        int EVPSignInitex(EVPMDCTX *ctx, const EVPMD *type, ENGINE *impl);
        int EVPSignUpdate(EVPMDCTX *ctx, const void *d, unsigned int cnt);
        int EVPSignFinal(EVPMDCTX *ctx,unsigned char *sig,unsigned int *s, EVPPKEY *pkey);

        void EVPSignInit(EVPMDCTX *ctx, const EVPMD *type);

        int EVPPKEYsize(EVPPKEY *pkey);

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

       EVPSignInitex() sets up signing context ccttxx to use digest ttyyppee from
       ENGINE iimmppll. ccttxx must be initialized with EVPMDCTXinit() before
       calling this function.

       EVPSignUpdate() hashes ccnntt bytes of data at dd into the signature
       context ccttxx. This function can be called several times on the same ccttxx
       to include additional data.

       EVPSignFinal() signs the data in ccttxx using the private key ppkkeeyy and
       places the signature in ssiigg. The number of bytes of data written (i.e.
       the length of the signature) will be written to the integer at ss, at
       most EVPPKEYsize(pkey) bytes will be written.

       EVPSignInit() initializes a signing context ccttxx to use the default
       implementation of digest ttyyppee.

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

RETURN VALUES
       EVPSignInitex(), EVPSignUpdate() and EVPSignFinal() return 1 for
       success and 0 for failure.

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

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

NNOOTTEESS
       The EEVVPP 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
       EVPDigestInit(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 EVPSignFinal() internally finalizes a copy of the digest
       context.  This means that calls to EVPSignUpdate() and EVPSignFinal()
       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 EVPMDCTXcleanup() or a
       memory leak will occur.

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

SEE ALSO
       EVPVerifyInit(3), EVPDigestInit(3), err(3), evp(3), hmac(3), md2(3),
       md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)

HISTORY       EVPSignInit(), EVPSignUpdate() and EVPSignFinal() are available in
       all versions of SSLeay and OpenSSL.

       EVPSignInitex() was added in OpenSSL 0.9.7.



0.9.7l                            2005-03-22                   EVPSignInit(3)