[netbsd-mini2440.git] / crypto / external / bsd / openssl / lib / libcrypto / man / EVP_PKEY_verify.3
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136 .IX Title "EVP_PKEY_verify 3"
137 .TH EVP_PKEY_verify 3 "2006-07-12" "1.1.0-dev" "OpenSSL"
138 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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140 .if n .ad l
141 .nh
142 .SH "NAME"
143 EVP_PKEY_verify_init, EVP_PKEY_verify \- signature verification using a public key algorithm
144 .SH "LIBRARY"
145 libcrypto, -lcrypto
146 .SH "SYNOPSIS"
147 .IX Header "SYNOPSIS"
148 .Vb 1
149 \& #include <openssl/evp.h>
150 \&
151 \& int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx);
152 \& int EVP_PKEY_verify(EVP_PKEY_CTX *ctx,
153 \& const unsigned char *sig, size_t siglen,
154 \& const unsigned char *tbs, size_t tbslen);
155 .Ve
156 .SH "DESCRIPTION"
157 .IX Header "DESCRIPTION"
158 The \fIEVP_PKEY_verify_init()\fR function initializes a public key algorithm
159 context using key \fBpkey\fR for a signature verification operation.
160 .PP
161 The \fIEVP_PKEY_verify()\fR function performs a public key verification operation
162 using \fBctx\fR. The signature is specified using the \fBsig\fR and
163 \&\fBsiglen\fR parameters. The verified data (i.e. the data believed originally
164 signed) is specified using the \fBtbs\fR and \fBtbslen\fR parameters.
165 .SH "NOTES"
166 .IX Header "NOTES"
167 After the call to \fIEVP_PKEY_verify_init()\fR algorithm specific control
168 operations can be performed to set any appropriate parameters for the
169 operation.
170 .PP
171 The function \fIEVP_PKEY_verify()\fR can be called more than once on the same
172 context if several operations are performed using the same parameters.
173 .SH "RETURN VALUES"
174 .IX Header "RETURN VALUES"
175 \&\fIEVP_PKEY_verify_init()\fR and \fIEVP_PKEY_verify()\fR return 1 if the verification was
176 successful and 0 if it failed. Unlike other functions the return value 0 from
177 \&\fIEVP_PKEY_verify()\fR only indicates that the signature did not not verify
178 successfully (that is tbs did not match the original data or the signature was
179 of invalid form) it is not an indication of a more serious error.
180 .PP
181 A negative value indicates an error other that signature verification failure.
182 In particular a return value of \-2 indicates the operation is not supported by
183 the public key algorithm.
184 .SH "EXAMPLE"
185 .IX Header "EXAMPLE"
186 Verify signature using PKCS#1 and \s-1SHA256\s0 digest:
187 .PP
188 .Vb 2
189 \& #include <openssl/evp.h>
190 \& #include <openssl/rsa.h>
191 \&
192 \& EVP_PKEY_CTX *ctx;
193 \& unsigned char *md, *sig;
194 \& size_t mdlen, siglen;
195 \& EVP_PKEY *verify_key;
196 \& /* NB: assumes verify_key, sig, siglen md and mdlen are already set up
197 \& * and that verify_key is an RSA public key
198 \& */
199 \& ctx = EVP_PKEY_CTX_new(verify_key);
200 \& if (!ctx)
201 \& /* Error occurred */
202 \& if (EVP_PKEY_verify_init(ctx) <= 0)
203 \& /* Error */
204 \& if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
205 \& /* Error */
206 \& if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
207 \& /* Error */
208 \&
209 \& /* Perform operation */
210 \& ret = EVP_PKEY_verify(ctx, md, mdlen, sig, siglen);
211 \&
212 \& /* ret == 1 indicates success, 0 verify failure and < 0 for some
213 \& * other error.
214 \& */
215 .Ve
216 .SH "SEE ALSO"
217 .IX Header "SEE ALSO"
218 \&\fIEVP_PKEY_CTX_new\fR\|(3),
219 \&\fIEVP_PKEY_encrypt\fR\|(3),
220 \&\fIEVP_PKEY_decrypt\fR\|(3),
221 \&\fIEVP_PKEY_sign\fR\|(3),
222 \&\fIEVP_PKEY_verifyrecover\fR\|(3),
223 \&\fIEVP_PKEY_derive\fR\|(3)
224 .SH "HISTORY"
225 .IX Header "HISTORY"
226 These functions were first added to OpenSSL 0.9.9.