2000-03-07 17:35:25 +00:00
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=pod
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=head1 NAME
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EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP signature verification functions
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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void EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
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void EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
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int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
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=head1 DESCRIPTION
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The EVP signature verification routines are a high level interface to digital
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signatures.
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2000-09-20 03:24:36 +00:00
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EVP_VerifyInit() initializes a verification context B<ctx> to using digest
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2000-03-07 17:35:25 +00:00
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B<type>: this will typically be supplied by a function such as EVP_sha1().
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EVP_VerifyUpdate() hashes B<cnt> bytes of data at B<d> into the
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verification context B<ctx>. This function can be called several times on the
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same B<ctx> to include additional data.
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EVP_VerifyFinal() verifies the data in B<ctx> using the public key B<pkey>
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and against the B<siglen> bytes at B<sigbuf>. After calling EVP_VerifyFinal()
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no additional calls to EVP_VerifyUpdate() can be made, but EVP_VerifyInit()
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can be called to initialize a new verification operation.
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2000-03-07 17:35:25 +00:00
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=head1 RETURN VALUES
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EVP_VerifyInit() and EVP_VerifyUpdate() do not return values.
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EVP_VerifyFinal() returns 1 for a correct signature, 0 for failure and -1 if some
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other error occurred.
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The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
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=head1 NOTES
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The B<EVP> interface to digital signatures should almost always be used in
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preference to the low level interfaces. This is because the code then becomes
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transparent to the algorithm used and much more flexible.
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Due to the link between message digests and public key algorithms the correct
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digest algorithm must be used with the correct public key type. A list of
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algorithms and associated public key algorithms appears in
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L<EVP_DigestInit(3)|EVP_DigestInit(3)>.
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=head1 BUGS
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Several of the functions do not return values: maybe they should. Although the
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internal digest operations will never fail some future hardware based operations
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might.
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=head1 SEE ALSO
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2000-09-23 07:16:17 +00:00
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L<evp(3)|evp(3)>,
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L<EVP_SignInit(3)|EVP_SignInit(3)>,
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L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>,
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L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
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L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>,
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L<sha(3)|sha(3)>, L<digest(1)|digest(1)>
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=head1 HISTORY
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EVP_VerifyInit(), EVP_VerifyUpdate() and EVP_VerifyFinal() are
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available in all versions of SSLeay and OpenSSL.
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=cut
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