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136 .\"
137 .IX Title "dsa 3"
138 .TH dsa 3 "2009-07-19" "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 dsa \- Digital Signature Algorithm
145 .SH "LIBRARY"
146 libcrypto, -lcrypto
147 .SH "SYNOPSIS"
148 .IX Header "SYNOPSIS"
149 .Vb 2
150 \& #include <openssl/dsa.h>
151 \& #include <openssl/engine.h>
152 \&
153 \& DSA * DSA_new(void);
154 \& void DSA_free(DSA *dsa);
155 \&
156 \& int DSA_size(const DSA *dsa);
157 \&
158 \& DSA * DSA_generate_parameters(int bits, unsigned char *seed,
159 \& int seed_len, int *counter_ret, unsigned long *h_ret,
160 \& void (*callback)(int, int, void *), void *cb_arg);
161 \&
162 \& DH * DSA_dup_DH(const DSA *r);
163 \&
164 \& int DSA_generate_key(DSA *dsa);
165 \&
166 \& int DSA_sign(int dummy, const unsigned char *dgst, int len,
167 \& unsigned char *sigret, unsigned int *siglen, DSA *dsa);
168 \& int DSA_sign_setup(DSA *dsa, BN_CTX *ctx, BIGNUM **kinvp,
169 \& BIGNUM **rp);
170 \& int DSA_verify(int dummy, const unsigned char *dgst, int len,
171 \& const unsigned char *sigbuf, int siglen, DSA *dsa);
172 \&
173 \& void DSA_set_default_method(const DSA_METHOD *meth);
174 \& const DSA_METHOD *DSA_get_default_method(void);
175 \& int DSA_set_method(DSA *dsa, const DSA_METHOD *meth);
176 \& DSA *DSA_new_method(ENGINE *engine);
177 \& const DSA_METHOD *DSA_OpenSSL(void);
178 \&
179 \& int DSA_get_ex_new_index(long argl, char *argp, int (*new_func)(),
180 \& int (*dup_func)(), void (*free_func)());
181 \& int DSA_set_ex_data(DSA *d, int idx, char *arg);
182 \& char *DSA_get_ex_data(DSA *d, int idx);
183 \&
184 \& DSA_SIG *DSA_SIG_new(void);
185 \& void DSA_SIG_free(DSA_SIG *a);
186 \& int i2d_DSA_SIG(const DSA_SIG *a, unsigned char **pp);
187 \& DSA_SIG *d2i_DSA_SIG(DSA_SIG **v, unsigned char **pp, long length);
188 \&
189 \& DSA_SIG *DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
190 \& int DSA_do_verify(const unsigned char *dgst, int dgst_len,
191 \& DSA_SIG *sig, DSA *dsa);
192 \&
193 \& DSA * d2i_DSAPublicKey(DSA **a, unsigned char **pp, long length);
194 \& DSA * d2i_DSAPrivateKey(DSA **a, unsigned char **pp, long length);
195 \& DSA * d2i_DSAparams(DSA **a, unsigned char **pp, long length);
196 \& int i2d_DSAPublicKey(const DSA *a, unsigned char **pp);
197 \& int i2d_DSAPrivateKey(const DSA *a, unsigned char **pp);
198 \& int i2d_DSAparams(const DSA *a,unsigned char **pp);
199 \&
200 \& int DSAparams_print(BIO *bp, const DSA *x);
201 \& int DSAparams_print_fp(FILE *fp, const DSA *x);
202 \& int DSA_print(BIO *bp, const DSA *x, int off);
203 \& int DSA_print_fp(FILE *bp, const DSA *x, int off);
204 .Ve
205 .SH "DESCRIPTION"
206 .IX Header "DESCRIPTION"
207 These functions implement the Digital Signature Algorithm (\s-1DSA\s0). The
208 generation of shared \s-1DSA\s0 parameters is described in
209 \&\fIDSA_generate_parameters\fR\|(3);
210 \&\fIDSA_generate_key\fR\|(3) describes how to
211 generate a signature key. Signature generation and verification are
212 described in \fIDSA_sign\fR\|(3).
213 .PP
214 The \fB\s-1DSA\s0\fR structure consists of several \s-1BIGNUM\s0 components.
215 .PP
216 .Vb 10
217 \& struct
218 \& {
219 \& BIGNUM *p; // prime number (public)
220 \& BIGNUM *q; // 160\-bit subprime, q | p\-1 (public)
221 \& BIGNUM *g; // generator of subgroup (public)
222 \& BIGNUM *priv_key; // private key x
223 \& BIGNUM *pub_key; // public key y = g^x
224 \& // ...
225 \& }
226 \& DSA;
227 .Ve
228 .PP
229 In public keys, \fBpriv_key\fR is \s-1NULL.\s0
230 .PP
231 Note that \s-1DSA\s0 keys may use non-standard \fB\s-1DSA_METHOD\s0\fR implementations,
232 either directly or by the use of \fB\s-1ENGINE\s0\fR modules. In some cases (eg. an
233 \&\s-1ENGINE\s0 providing support for hardware-embedded keys), these \s-1BIGNUM\s0 values
234 will not be used by the implementation or may be used for alternative data
235 storage. For this reason, applications should generally avoid using \s-1DSA\s0
236 structure elements directly and instead use \s-1API\s0 functions to query or
237 modify keys.
238 .SH "CONFORMING TO"
239 .IX Header "CONFORMING TO"
240 \&\s-1US\s0 Federal Information Processing Standard \s-1FIPS 186 \s0(Digital Signature
241 Standard, \s-1DSS\s0), \s-1ANSI X9.30\s0
242 .SH "SEE ALSO"
243 .IX Header "SEE ALSO"
244 \&\fIopenssl_bn\fR\|(3), \fIopenssl_dh\fR\|(3), \fIopenssl_err\fR\|(3), \fIopenssl_rand\fR\|(3),
245 \&\fIopenssl_rsa\fR\|(3), \fIopenssl_sha\fR\|(3), \fIengine\fR\|(3),
246 \&\fIDSA_new\fR\|(3),
247 \&\fIDSA_size\fR\|(3),
248 \&\fIDSA_generate_parameters\fR\|(3),
249 \&\fIDSA_dup_DH\fR\|(3),
250 \&\fIDSA_generate_key\fR\|(3),
251 \&\fIDSA_sign\fR\|(3), \fIDSA_set_method\fR\|(3),
252 \&\fIDSA_get_ex_new_index\fR\|(3),
253 \&\fIRSA_print\fR\|(3)