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137 .IX Title "EVP_PKEY_verify 3"
138 .TH EVP_PKEY_verify 3 "2013-02-05" "1.0.1n" "OpenSSL"
139 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
140 .\" way too many mistakes in technical documents.
141 .if n .ad l
142 .nh
143 .SH "NAME"
144 EVP_PKEY_verify_init, EVP_PKEY_verify \- signature verification using a public key algorithm
145 .SH "LIBRARY"
146 libcrypto, -lcrypto
147 .SH "SYNOPSIS"
148 .IX Header "SYNOPSIS"
149 .Vb 1
150 \& #include <openssl/evp.h>
151 \&
152 \& int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx);
153 \& int EVP_PKEY_verify(EVP_PKEY_CTX *ctx,
154 \& const unsigned char *sig, size_t siglen,
155 \& const unsigned char *tbs, size_t tbslen);
156 .Ve
157 .SH "DESCRIPTION"
158 .IX Header "DESCRIPTION"
159 The \fIEVP_PKEY_verify_init()\fR function initializes a public key algorithm
160 context using key \fBpkey\fR for a signature verification operation.
161 .PP
162 The \fIEVP_PKEY_verify()\fR function performs a public key verification operation
163 using \fBctx\fR. The signature is specified using the \fBsig\fR and
164 \&\fBsiglen\fR parameters. The verified data (i.e. the data believed originally
165 signed) is specified using the \fBtbs\fR and \fBtbslen\fR parameters.
166 .SH "NOTES"
167 .IX Header "NOTES"
168 After the call to \fIEVP_PKEY_verify_init()\fR algorithm specific control
169 operations can be performed to set any appropriate parameters for the
170 operation.
171 .PP
172 The function \fIEVP_PKEY_verify()\fR can be called more than once on the same
173 context if several operations are performed using the same parameters.
174 .SH "RETURN VALUES"
175 .IX Header "RETURN VALUES"
176 \&\fIEVP_PKEY_verify_init()\fR and \fIEVP_PKEY_verify()\fR return 1 if the verification was
177 successful and 0 if it failed. Unlike other functions the return value 0 from
178 \&\fIEVP_PKEY_verify()\fR only indicates that the signature did not not verify
179 successfully (that is tbs did not match the original data or the signature was
180 of invalid form) it is not an indication of a more serious error.
181 .PP
182 A negative value indicates an error other that signature verification failure.
183 In particular a return value of \-2 indicates the operation is not supported by
184 the public key algorithm.
185 .SH "EXAMPLE"
186 .IX Header "EXAMPLE"
187 Verify signature using PKCS#1 and \s-1SHA256\s0 digest:
188 .PP
189 .Vb 2
190 \& #include <openssl/evp.h>
191 \& #include <openssl/rsa.h>
192 \&
193 \& EVP_PKEY_CTX *ctx;
194 \& unsigned char *md, *sig;
195 \& size_t mdlen, siglen;
196 \& EVP_PKEY *verify_key;
197 \& /* NB: assumes verify_key, sig, siglen md and mdlen are already set up
198 \& * and that verify_key is an RSA public key
199 \& */
200 \& ctx = EVP_PKEY_CTX_new(verify_key);
201 \& if (!ctx)
202 \& /* Error occurred */
203 \& if (EVP_PKEY_verify_init(ctx) <= 0)
204 \& /* Error */
205 \& if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
206 \& /* Error */
207 \& if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
208 \& /* Error */
209 \&
210 \& /* Perform operation */
211 \& ret = EVP_PKEY_verify(ctx, sig, siglen, md, mdlen);
212 \&
213 \& /* ret == 1 indicates success, 0 verify failure and < 0 for some
214 \& * other error.
215 \& */
216 .Ve
217 .SH "SEE ALSO"
218 .IX Header "SEE ALSO"
219 \&\fIEVP_PKEY_CTX_new\fR\|(3),
220 \&\fIEVP_PKEY_encrypt\fR\|(3),
221 \&\fIEVP_PKEY_decrypt\fR\|(3),
222 \&\fIEVP_PKEY_sign\fR\|(3),
223 \&\fIEVP_PKEY_verify_recover\fR\|(3),
224 \&\fIEVP_PKEY_derive\fR\|(3)
225 .SH "HISTORY"
226 .IX Header "HISTORY"
227 These functions were first added to OpenSSL 1.0.0.