svn merge -r514:HEAD ^/branches/released .

1 files changed, 82 insertions, 0 deletions

diff --git a/openssl/doc/crypto/EVP_DigestVerifyInit.pod b/openssl/doc/crypto/EVP_DigestVerifyInit.pod
new file mode 100644
index 000000000..f22448897
--- /dev/null
+++ b/openssl/doc/crypto/EVP_DigestVerifyInit.pod
@@ -0,0 +1,82 @@
+=pod
+
+=head1 NAME
+
+EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal - EVP signature verification functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/evp.h>
+
+ int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
+			const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
+ int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
+ int EVP_DigestVerifyFinal(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_DigestVerifyInit() sets up verification context B<ctx> to use digest
+B<type> from ENGINE B<impl> and public 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 verification operation will be written to B<*pctx>: this
+can be used to set alternative verification options.
+
+EVP_DigestVerifyUpdate() hashes B<cnt> bytes of data at B<d> into the
+verification context B<ctx>. This function can be called several times on the
+same B<ctx> to include additional data. This function is currently implemented
+using a macro.
+
+EVP_DigestVerifyFinal() verifies the data in B<ctx> against the signature in
+B<sig> of length B<siglen>.
+
+=head1 RETURN VALUES
+
+EVP_DigestVerifyInit() and EVP_DigestVerifyUpdate() 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.
+
+Unlike other functions the return value 0 from EVP_DigestVerifyFinal() only
+indicates that the signature did not not verify successfully (that is tbs did
+not match the original data or the signature was of invalid form) it is not an
+indication of a more serious error.
+
+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_DigestVerifyFinal() internally finalizes a copy of the digest
+context. This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can
+be called later to digest and verify 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 SEE ALSO
+
+L<EVP_DigestSignInit(3)|EVP_DigestSignInit(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_DigestVerifyInit(), EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal() 
+were first added to OpenSSL 1.0.0.
+
+=cut