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[dragonfly.git] / secure / lib / libcrypto / man / EVP_VerifyInit.3
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138.\" ======================================================================
139.\"
140.IX Title "EVP_VerifyInit 3"
141.TH EVP_VerifyInit 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal \- \s-1EVP\s0 signature verification functions
145.SH "SYNOPSIS"
146.IX Header "SYNOPSIS"
147.Vb 1
148\& #include <openssl/evp.h>
149.Ve
150.Vb 3
151\& int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
152\& int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
153\& int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
154.Ve
155.Vb 1
156\& int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
157.Ve
158.SH "DESCRIPTION"
159.IX Header "DESCRIPTION"
160The \s-1EVP\s0 signature verification routines are a high level interface to digital
161signatures.
162.PP
163\&\fIEVP_VerifyInit_ex()\fR sets up verification context \fBctx\fR to use digest
164\&\fBtype\fR from \s-1ENGINE\s0 \fBimpl\fR. \fBctx\fR must be initialized by calling
165\&\fIEVP_MD_CTX_init()\fR before calling this function.
166.PP
167\&\fIEVP_VerifyUpdate()\fR hashes \fBcnt\fR bytes of data at \fBd\fR into the
168verification context \fBctx\fR. This function can be called several times on the
169same \fBctx\fR to include additional data.
170.PP
171\&\fIEVP_VerifyFinal()\fR verifies the data in \fBctx\fR using the public key \fBpkey\fR
172and against the \fBsiglen\fR bytes at \fBsigbuf\fR.
173.PP
174\&\fIEVP_VerifyInit()\fR initializes verification context \fBctx\fR to use the default
175implementation of digest \fBtype\fR.
176.SH "RETURN VALUES"
177.IX Header "RETURN VALUES"
178\&\fIEVP_VerifyInit_ex()\fR and \fIEVP_VerifyUpdate()\fR return 1 for success and 0 for
179failure.
180.PP
181\&\fIEVP_VerifyFinal()\fR returns 1 for a correct signature, 0 for failure and \-1 if some
182other error occurred.
183.PP
184The error codes can be obtained by ERR_get_error(3).
185.SH "NOTES"
186.IX Header "NOTES"
187The \fB\s-1EVP\s0\fR interface to digital signatures should almost always be used in
188preference to the low level interfaces. This is because the code then becomes
189transparent to the algorithm used and much more flexible.
190.PP
191Due to the link between message digests and public key algorithms the correct
192digest algorithm must be used with the correct public key type. A list of
193algorithms and associated public key algorithms appears in
194EVP_DigestInit(3).
195.PP
196The call to \fIEVP_VerifyFinal()\fR internally finalizes a copy of the digest context.
197This means that calls to \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR can be called
198later to digest and verify additional data.
199.PP
200Since only a copy of the digest context is ever finalized the context must
201be cleaned up after use by calling \fIEVP_MD_CTX_cleanup()\fR or a memory leak
202will occur.
203.SH "BUGS"
204.IX Header "BUGS"
205Older versions of this documentation wrongly stated that calls to
206\&\fIEVP_VerifyUpdate()\fR could not be made after calling \fIEVP_VerifyFinal()\fR.
207.SH "SEE ALSO"
208.IX Header "SEE ALSO"
209evp(3),
210EVP_SignInit(3),
211EVP_DigestInit(3), err(3),
212evp(3), hmac(3), md2(3),
213md5(3), mdc2(3), ripemd(3),
214sha(3), dgst(1)
215.SH "HISTORY"
216.IX Header "HISTORY"
217\&\fIEVP_VerifyInit()\fR, \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR are
218available in all versions of SSLeay and OpenSSL.
219.PP
220\&\fIEVP_VerifyInit_ex()\fR was added in OpenSSL 0.9.7