Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / EVP_VerifyInit.3
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124.\" ========================================================================
125.\"
126.IX Title "EVP_VerifyInit 3"
e3261593 127.TH EVP_VerifyInit 3 "2012-01-04" "1.0.0f" "OpenSSL"
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128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
984263bc 132.SH "NAME"
74dab6c2 133EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal \- EVP signature verification functions
984263bc 134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
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136.Vb 1
137\& #include <openssl/evp.h>
e257b235 138\&
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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);
e257b235 142\&
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143\& int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
144.Ve
145.SH "DESCRIPTION"
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146.IX Header "DESCRIPTION"
147The \s-1EVP\s0 signature verification routines are a high level interface to digital
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148signatures.
149.PP
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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.
984263bc 153.PP
8b0cefbb 154\&\fIEVP_VerifyUpdate()\fR hashes \fBcnt\fR bytes of data at \fBd\fR into the
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155verification context \fBctx\fR. This function can be called several times on the
156same \fBctx\fR to include additional data.
157.PP
8b0cefbb 158\&\fIEVP_VerifyFinal()\fR verifies the data in \fBctx\fR using the public key \fBpkey\fR
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159and against the \fBsiglen\fR bytes at \fBsigbuf\fR.
160.PP
8b0cefbb 161\&\fIEVP_VerifyInit()\fR initializes verification context \fBctx\fR to use the default
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162implementation of digest \fBtype\fR.
163.SH "RETURN VALUES"
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164.IX Header "RETURN VALUES"
165\&\fIEVP_VerifyInit_ex()\fR and \fIEVP_VerifyUpdate()\fR return 1 for success and 0 for
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166failure.
167.PP
8b0cefbb 168\&\fIEVP_VerifyFinal()\fR returns 1 for a correct signature, 0 for failure and \-1 if some
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169other error occurred.
170.PP
8b0cefbb 171The error codes can be obtained by \fIERR_get_error\fR\|(3).
984263bc 172.SH "NOTES"
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173.IX Header "NOTES"
174The \fB\s-1EVP\s0\fR interface to digital signatures should almost always be used in
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175preference to the low level interfaces. This is because the code then becomes
176transparent to the algorithm used and much more flexible.
177.PP
178Due to the link between message digests and public key algorithms the correct
179digest algorithm must be used with the correct public key type. A list of
180algorithms and associated public key algorithms appears in
8b0cefbb 181\&\fIEVP_DigestInit\fR\|(3).
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182.PP
183The call to \fIEVP_VerifyFinal()\fR internally finalizes a copy of the digest context.
184This means that calls to \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR can be called
185later to digest and verify additional data.
186.PP
187Since only a copy of the digest context is ever finalized the context must
188be cleaned up after use by calling \fIEVP_MD_CTX_cleanup()\fR or a memory leak
189will occur.
190.SH "BUGS"
8b0cefbb 191.IX Header "BUGS"
984263bc 192Older versions of this documentation wrongly stated that calls to
8b0cefbb 193\&\fIEVP_VerifyUpdate()\fR could not be made after calling \fIEVP_VerifyFinal()\fR.
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194.PP
195Since the public key is passed in the call to \fIEVP_SignFinal()\fR any error
196relating to the private key (for example an unsuitable key and digest
197combination) will not be indicated until after potentially large amounts of
198data have been passed through \fIEVP_SignUpdate()\fR.
199.PP
200It is not possible to change the signing parameters using these function.
201.PP
202The previous two bugs are fixed in the newer EVP_VerifyDigest*() function.
984263bc 203.SH "SEE ALSO"
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204.IX Header "SEE ALSO"
205\&\fIevp\fR\|(3),
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)
984263bc 211.SH "HISTORY"
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212.IX Header "HISTORY"
213\&\fIEVP_VerifyInit()\fR, \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR are
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214available in all versions of SSLeay and OpenSSL.
215.PP
8b0cefbb 216\&\fIEVP_VerifyInit_ex()\fR was added in OpenSSL 0.9.7