Merge branch 'vendor/OPENSSL'
[dragonfly.git] / secure / lib / libcrypto / man / EVP_VerifyInit.3
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129.\" ========================================================================
130.\"
131.IX Title "EVP_VerifyInit 3"
18ed9402 132.TH EVP_VerifyInit 3 "2008-09-27" "0.9.8i" "OpenSSL"
984263bc 133.SH "NAME"
74dab6c2 134EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal \- EVP signature verification functions
984263bc 135.SH "SYNOPSIS"
8b0cefbb 136.IX Header "SYNOPSIS"
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137.Vb 1
138\& #include <openssl/evp.h>
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139.Ve
140.PP
141.Vb 3
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142\& int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
143\& int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
144\& int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
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145.Ve
146.PP
147.Vb 1
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148\& int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
149.Ve
150.SH "DESCRIPTION"
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151.IX Header "DESCRIPTION"
152The \s-1EVP\s0 signature verification routines are a high level interface to digital
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153signatures.
154.PP
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155\&\fIEVP_VerifyInit_ex()\fR sets up verification context \fBctx\fR to use digest
156\&\fBtype\fR from \s-1ENGINE\s0 \fBimpl\fR. \fBctx\fR must be initialized by calling
157\&\fIEVP_MD_CTX_init()\fR before calling this function.
984263bc 158.PP
8b0cefbb 159\&\fIEVP_VerifyUpdate()\fR hashes \fBcnt\fR bytes of data at \fBd\fR into the
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160verification context \fBctx\fR. This function can be called several times on the
161same \fBctx\fR to include additional data.
162.PP
8b0cefbb 163\&\fIEVP_VerifyFinal()\fR verifies the data in \fBctx\fR using the public key \fBpkey\fR
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164and against the \fBsiglen\fR bytes at \fBsigbuf\fR.
165.PP
8b0cefbb 166\&\fIEVP_VerifyInit()\fR initializes verification context \fBctx\fR to use the default
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167implementation of digest \fBtype\fR.
168.SH "RETURN VALUES"
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169.IX Header "RETURN VALUES"
170\&\fIEVP_VerifyInit_ex()\fR and \fIEVP_VerifyUpdate()\fR return 1 for success and 0 for
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171failure.
172.PP
8b0cefbb 173\&\fIEVP_VerifyFinal()\fR returns 1 for a correct signature, 0 for failure and \-1 if some
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174other error occurred.
175.PP
8b0cefbb 176The error codes can be obtained by \fIERR_get_error\fR\|(3).
984263bc 177.SH "NOTES"
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178.IX Header "NOTES"
179The \fB\s-1EVP\s0\fR interface to digital signatures should almost always be used in
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180preference to the low level interfaces. This is because the code then becomes
181transparent to the algorithm used and much more flexible.
182.PP
183Due to the link between message digests and public key algorithms the correct
184digest algorithm must be used with the correct public key type. A list of
185algorithms and associated public key algorithms appears in
8b0cefbb 186\&\fIEVP_DigestInit\fR\|(3).
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187.PP
188The call to \fIEVP_VerifyFinal()\fR internally finalizes a copy of the digest context.
189This means that calls to \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR can be called
190later to digest and verify additional data.
191.PP
192Since only a copy of the digest context is ever finalized the context must
193be cleaned up after use by calling \fIEVP_MD_CTX_cleanup()\fR or a memory leak
194will occur.
195.SH "BUGS"
8b0cefbb 196.IX Header "BUGS"
984263bc 197Older versions of this documentation wrongly stated that calls to
8b0cefbb 198\&\fIEVP_VerifyUpdate()\fR could not be made after calling \fIEVP_VerifyFinal()\fR.
984263bc 199.SH "SEE ALSO"
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200.IX Header "SEE ALSO"
201\&\fIevp\fR\|(3),
202\&\fIEVP_SignInit\fR\|(3),
203\&\fIEVP_DigestInit\fR\|(3), \fIerr\fR\|(3),
204\&\fIevp\fR\|(3), \fIhmac\fR\|(3), \fImd2\fR\|(3),
205\&\fImd5\fR\|(3), \fImdc2\fR\|(3), \fIripemd\fR\|(3),
206\&\fIsha\fR\|(3), \fIdgst\fR\|(1)
984263bc 207.SH "HISTORY"
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208.IX Header "HISTORY"
209\&\fIEVP_VerifyInit()\fR, \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR are
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210available in all versions of SSLeay and OpenSSL.
211.PP
8b0cefbb 212\&\fIEVP_VerifyInit_ex()\fR was added in OpenSSL 0.9.7