Manual Reference Pages - EVP_DIGESTSIGNUPDATE (3)
EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal - EVP signing functions
int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);
The EVP signature routines are a high level interface to digital signatures.
EVP_DigestSignInit() sets up signing context ctx to use digest type from
ENGINE impl and private key pkey. ctx must be initialized with
EVP_MD_CTX_init() before calling this function. If pctx is not NULL the
EVP_PKEY_CTX of the signing operation will be written to *pctx: this can
be used to set alternative signing options.
EVP_DigestSignUpdate() 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. This function is currently implemented
usig a macro.
EVP_DigestSignFinal() signs the data in ctx places the signature in sig.
If sig is NULL then the maximum size of the output buffer is written to
the siglen parameter. If sig is not NULL then before the call the
siglen parameter should contain the length of the sig buffer, if the
call is successful the signature is written to sig and the amount of data
written to siglen.
EVP_DigestSignInit() EVP_DigestSignUpdate() and EVP_DigestSignaFinal() return
1 for success and 0 or a negative value for failure. In particular a return
value of -2 indicates the operation is not supported by the public key
The error codes can be obtained from ERR_get_error(3).
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.
In previous versions of OpenSSL there was a link between message digest types
and public key algorithms. This meant that clone digests such as EVP_dss1()
needed to be used to sign using SHA1 and DSA. This is no longer necessary and
the use of clone digest is now discouraged.
For some key types and parameters the random number generator must be seeded
or the operation will fail.
The call to EVP_DigestSignFinal() internally finalizes a copy of the digest
context. This means that calls to EVP_DigestSignUpdate() and
EVP_DigestSignFinal() 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
The use of EVP_PKEY_size() with these functions is discouraged because some
signature operations may have a signature length which depends on the
parameters set. As a result EVP_PKEY_size() would have to return a value
which indicates the maximum possible signature for any set of parameters.
evp(3), hmac(3), md2(3),
md5(3), mdc2(3), ripemd(3),
EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
were first added to OpenSSL 1.0.0.
|1.0.1s ||EVP_DIGESTSIGNINIT (3) ||2016-03-01 |
Visit the GSP FreeBSD Man Page Interface.
Output converted with manServer 1.07.