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124 .\" ========================================================================
126 .IX Title "EVP_VerifyInit 3"
127 .TH EVP_VerifyInit 3 "2014-04-07" "1.0.1g" "OpenSSL"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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133 EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal \- EVP signature verification functions
135 .IX Header "SYNOPSIS"
137 \& #include <openssl/evp.h>
139 \& int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
140 \& int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
141 \& int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
143 \& int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
146 .IX Header "DESCRIPTION"
147 The \s-1EVP\s0 signature verification routines are a high level interface to digital
150 \&\fIEVP_VerifyInit_ex()\fR sets up verification context \fBctx\fR to use digest
151 \&\fBtype\fR from \s-1ENGINE\s0 \fBimpl\fR. \fBctx\fR must be initialized by calling
152 \&\fIEVP_MD_CTX_init()\fR before calling this function.
154 \&\fIEVP_VerifyUpdate()\fR hashes \fBcnt\fR bytes of data at \fBd\fR into the
155 verification context \fBctx\fR. This function can be called several times on the
156 same \fBctx\fR to include additional data.
158 \&\fIEVP_VerifyFinal()\fR verifies the data in \fBctx\fR using the public key \fBpkey\fR
159 and against the \fBsiglen\fR bytes at \fBsigbuf\fR.
161 \&\fIEVP_VerifyInit()\fR initializes verification context \fBctx\fR to use the default
162 implementation of digest \fBtype\fR.
164 .IX Header "RETURN VALUES"
165 \&\fIEVP_VerifyInit_ex()\fR and \fIEVP_VerifyUpdate()\fR return 1 for success and 0 for
168 \&\fIEVP_VerifyFinal()\fR returns 1 for a correct signature, 0 for failure and \-1 if some
169 other error occurred.
171 The error codes can be obtained by \fIERR_get_error\fR\|(3).
174 The \fB\s-1EVP\s0\fR interface to digital signatures should almost always be used in
175 preference to the low level interfaces. This is because the code then becomes
176 transparent to the algorithm used and much more flexible.
178 Due to the link between message digests and public key algorithms the correct
179 digest algorithm must be used with the correct public key type. A list of
180 algorithms and associated public key algorithms appears in
181 \&\fIEVP_DigestInit\fR\|(3).
183 The call to \fIEVP_VerifyFinal()\fR internally finalizes a copy of the digest context.
184 This means that calls to \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR can be called
185 later to digest and verify additional data.
187 Since only a copy of the digest context is ever finalized the context must
188 be cleaned up after use by calling \fIEVP_MD_CTX_cleanup()\fR or a memory leak
192 Older versions of this documentation wrongly stated that calls to
193 \&\fIEVP_VerifyUpdate()\fR could not be made after calling \fIEVP_VerifyFinal()\fR.
195 Since the public key is passed in the call to \fIEVP_SignFinal()\fR any error
196 relating to the private key (for example an unsuitable key and digest
197 combination) will not be indicated until after potentially large amounts of
198 data have been passed through \fIEVP_SignUpdate()\fR.
200 It is not possible to change the signing parameters using these function.
202 The previous two bugs are fixed in the newer EVP_VerifyDigest*() function.
204 .IX Header "SEE ALSO"
206 \&\fIEVP_SignInit\fR\|(3),
207 \&\fIEVP_DigestInit\fR\|(3), \fIerr\fR\|(3),
208 \&\fIevp\fR\|(3), \fIhmac\fR\|(3), \fImd2\fR\|(3),
209 \&\fImd5\fR\|(3), \fImdc2\fR\|(3), \fIripemd\fR\|(3),
210 \&\fIsha\fR\|(3), \fIdgst\fR\|(1)
213 \&\fIEVP_VerifyInit()\fR, \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR are
214 available in all versions of SSLeay and OpenSSL.
216 \&\fIEVP_VerifyInit_ex()\fR was added in OpenSSL 0.9.7