Index: openssl/doc/crypto/EVP_DigestSignInit.pod |
=================================================================== |
--- openssl/doc/crypto/EVP_DigestSignInit.pod (revision 0) |
+++ openssl/doc/crypto/EVP_DigestSignInit.pod (revision 0) |
@@ -0,0 +1,87 @@ |
+=pod |
+ |
+=head1 NAME |
+ |
+EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal - EVP signing functions |
+ |
+=head1 SYNOPSIS |
+ |
+ #include <openssl/evp.h> |
+ |
+ 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); |
+ |
+=head1 DESCRIPTION |
+ |
+The EVP signature routines are a high level interface to digital signatures. |
+ |
+EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from |
+ENGINE B<impl> and private key B<pkey>. B<ctx> must be initialized with |
+EVP_MD_CTX_init() before calling this function. If B<pctx> is not NULL the |
+EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can |
+be used to set alternative signing options. |
+ |
+EVP_DigestSignUpdate() 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. This function is currently implemented |
+usig a macro. |
+ |
+EVP_DigestSignFinal() signs the data in B<ctx> places the signature in B<sig>. |
+If B<sig> is B<NULL> then the maximum size of the output buffer is written to |
+the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the |
+B<siglen> parameter should contain the length of the B<sig> buffer, if the |
+call is successful the signature is written to B<sig> and the amount of data |
+written to B<siglen>. |
+ |
+=head1 RETURN VALUES |
+ |
+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 |
+algorithm. |
+ |
+The error codes can be obtained from 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. |
+ |
+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 |
+will occur. |
+ |
+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. |
+ |
+=head1 SEE ALSO |
+ |
+L<EVP_DigestVerifyInit(3)|EVP_DigestVerifyInit(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_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal() |
+were first added to OpenSSL 1.0.0. |
+ |
+=cut |