- update OpenSSL to 0.9.8
[dragonfly.git] / secure / lib / libcrypto / man / ecdsa.3
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129.\" ========================================================================
130.\"
131.IX Title "ecdsa 3"
132.TH ecdsa 3 "2005-07-06" "0.9.8" "OpenSSL"
133.SH "NAME"
134ecdsa \- Elliptic Curve Digital Signature Algorithm
135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS"
137.Vb 1
138\& #include <openssl/ecdsa.h>
139.Ve
140.PP
141.Vb 5
142\& ECDSA_SIG* ECDSA_SIG_new(void);
143\& void ECDSA_SIG_free(ECDSA_SIG *sig);
144\& int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
145\& ECDSA_SIG* d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp,
146\& long len);
147.Ve
148.PP
149.Vb 20
150\& ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
151\& EC_KEY *eckey);
152\& ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
153\& const BIGNUM *kinv, const BIGNUM *rp,
154\& EC_KEY *eckey);
155\& int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
156\& const ECDSA_SIG *sig, EC_KEY* eckey);
157\& int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
158\& BIGNUM **kinv, BIGNUM **rp);
159\& int ECDSA_sign(int type, const unsigned char *dgst,
160\& int dgstlen, unsigned char *sig,
161\& unsigned int *siglen, EC_KEY *eckey);
162\& int ECDSA_sign_ex(int type, const unsigned char *dgst,
163\& int dgstlen, unsigned char *sig,
164\& unsigned int *siglen, const BIGNUM *kinv,
165\& const BIGNUM *rp, EC_KEY *eckey);
166\& int ECDSA_verify(int type, const unsigned char *dgst,
167\& int dgstlen, const unsigned char *sig,
168\& int siglen, EC_KEY *eckey);
169\& int ECDSA_size(const EC_KEY *eckey);
170.Ve
171.PP
172.Vb 4
173\& const ECDSA_METHOD* ECDSA_OpenSSL(void);
174\& void ECDSA_set_default_method(const ECDSA_METHOD *meth);
175\& const ECDSA_METHOD* ECDSA_get_default_method(void);
176\& int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
177.Ve
178.PP
179.Vb 6
180\& int ECDSA_get_ex_new_index(long argl, void *argp,
181\& CRYPTO_EX_new *new_func,
182\& CRYPTO_EX_dup *dup_func,
183\& CRYPTO_EX_free *free_func);
184\& int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
185\& void* ECDSA_get_ex_data(EC_KEY *d, int idx);
186.Ve
187.SH "DESCRIPTION"
188.IX Header "DESCRIPTION"
189The \fB\s-1ECDSA_SIG\s0\fR structure consists of two BIGNUMs for the
190r and s value of a \s-1ECDSA\s0 signature (see X9.62 or \s-1FIPS\s0 186\-2).
191.PP
192.Vb 5
193\& struct
194\& {
195\& BIGNUM *r;
196\& BIGNUM *s;
197\& } ECDSA_SIG;
198.Ve
199.PP
200\&\fIECDSA_SIG_new()\fR allocates a new \fB\s-1ECDSA_SIG\s0\fR structure (note: this
201function also allocates the BIGNUMs) and initialize it.
202.PP
203\&\fIECDSA_SIG_free()\fR frees the \fB\s-1ECDSA_SIG\s0\fR structure \fBsig\fR.
204.PP
205\&\fIi2d_ECDSA_SIG()\fR creates the \s-1DER\s0 encoding of the \s-1ECDSA\s0 signature
206\&\fBsig\fR and writes the encoded signature to \fB*pp\fR (note: if \fBpp\fR
207is \s-1NULL\s0 \fBi2d_ECDSA_SIG\fR returns the expected length in bytes of
208the \s-1DER\s0 encoded signature). \fBi2d_ECDSA_SIG\fR returns the length
209of the \s-1DER\s0 encoded signature (or 0 on error).
210.PP
211\&\fId2i_ECDSA_SIG()\fR decodes a \s-1DER\s0 encoded \s-1ECDSA\s0 signature and returns
212the decoded signature in a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure.
213\&\fB*sig\fR points to the buffer containing the \s-1DER\s0 encoded signature
214of size \fBlen\fR.
215.PP
216\&\fIECDSA_size()\fR returns the maximum length of a \s-1DER\s0 encoded
217\&\s-1ECDSA\s0 signature created with the private \s-1EC\s0 key \fBeckey\fR.
218.PP
219\&\fIECDSA_sign_setup()\fR may be used to precompute parts of the
220signing operation. \fBeckey\fR is the private \s-1EC\s0 key and \fBctx\fR
221is a pointer to \fB\s-1BN_CTX\s0\fR structure (or \s-1NULL\s0). The precomputed
222values or returned in \fBkinv\fR and \fBrp\fR and can be used in a
223later call to \fBECDSA_sign_ex\fR or \fBECDSA_do_sign_ex\fR.
224.PP
225\&\fIECDSA_sign()\fR is wrapper function for ECDSA_sign_ex with \fBkinv\fR
226and \fBrp\fR set to \s-1NULL\s0.
227.PP
228\&\fIECDSA_sign_ex()\fR computes a digital signature of the \fBdgstlen\fR bytes
229hash value \fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR and the optional
230pre-computed values \fBkinv\fR and \fBrp\fR. The \s-1DER\s0 encoded signatures is
231stored in \fBsig\fR and it's length is returned in \fBsig_len\fR. Note: \fBsig\fR
232must point to \fBECDSA_size\fR bytes of memory. The parameter \fBtype\fR
233is ignored.
234.PP
235\&\fIECDSA_verify()\fR verifies that the signature in \fBsig\fR of size
236\&\fBsiglen\fR is a valid \s-1ECDSA\s0 signature of the hash value
237value \fBdgst\fR of size \fBdgstlen\fR using the public key \fBeckey\fR.
238The parameter \fBtype\fR is ignored.
239.PP
240\&\fIECDSA_do_sign()\fR is wrapper function for ECDSA_do_sign_ex with \fBkinv\fR
241and \fBrp\fR set to \s-1NULL\s0.
242.PP
243\&\fIECDSA_do_sign_ex()\fR computes a digital signature of the \fBdgst_len\fR
244bytes hash value \fBdgst\fR using the private key \fBeckey\fR and the
245optional pre-computed values \fBkinv\fR and \fBrp\fR. The signature is
246returned in a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error).
247.PP
248\&\fIECDSA_do_verify()\fR verifies that the signature \fBsig\fR is a valid
249\&\s-1ECDSA\s0 signature of the hash value \fBdgst\fR of size \fBdgst_len\fR
250using the public key \fBeckey\fR.
251.SH "RETURN VALUES"
252.IX Header "RETURN VALUES"
253\&\fIECDSA_size()\fR returns the maximum length signature or 0 on error.
254.PP
255\&\fIECDSA_sign_setup()\fR and \fIECDSA_sign()\fR return 1 if successful or \-1
256on error.
257.PP
258\&\fIECDSA_verify()\fR and \fIECDSA_do_verify()\fR return 1 for a valid
259signature, 0 for an invalid signature and \-1 on error.
260The error codes can be obtained by \fIERR_get_error\fR\|(3).
261.SH "EXAMPLES"
262.IX Header "EXAMPLES"
263Creating a \s-1ECDSA\s0 signature of given \s-1SHA\-1\s0 hash value using the
264named curve secp192k1.
265.PP
266First step: create a \s-1EC_KEY\s0 object (note: this part is \fBnot\fR \s-1ECDSA\s0
267specific)
268.PP
269.Vb 16
270\& int ret;
271\& ECDSA_SIG *sig;
272\& EC_KEY *eckey = EC_KEY_new();
273\& if (eckey == NULL)
274\& {
275\& /* error */
276\& }
277\& key->group = EC_GROUP_new_by_nid(NID_secp192k1);
278\& if (key->group == NULL)
279\& {
280\& /* error */
281\& }
282\& if (!EC_KEY_generate_key(eckey))
283\& {
284\& /* error */
285\& }
286.Ve
287.PP
288Second step: compute the \s-1ECDSA\s0 signature of a \s-1SHA\-1\s0 hash value
289using \fBECDSA_do_sign\fR
290.PP
291.Vb 5
292\& sig = ECDSA_do_sign(digest, 20, eckey);
293\& if (sig == NULL)
294\& {
295\& /* error */
296\& }
297.Ve
298.PP
299or using \fBECDSA_sign\fR
300.PP
301.Vb 9
302\& unsigned char *buffer, *pp;
303\& int buf_len;
304\& buf_len = ECDSA_size(eckey);
305\& buffer = OPENSSL_malloc(buf_len);
306\& pp = buffer;
307\& if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
308\& {
309\& /* error */
310\& }
311.Ve
312.PP
313Third step: verify the created \s-1ECDSA\s0 signature using \fBECDSA_do_verify\fR
314.PP
315.Vb 1
316\& ret = ECDSA_do_verify(digest, 20, sig, eckey);
317.Ve
318.PP
319or using \fBECDSA_verify\fR
320.PP
321.Vb 1
322\& ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
323.Ve
324.PP
325and finally evaluate the return value:
326.PP
327.Vb 12
328\& if (ret == -1)
329\& {
330\& /* error */
331\& }
332\& else if (ret == 0)
333\& {
334\& /* incorrect signature */
335\& }
336\& else /* ret == 1 */
337\& {
338\& /* signature ok */
339\& }
340.Ve
341.SH "CONFORMING TO"
342.IX Header "CONFORMING TO"
343\&\s-1ANSI\s0 X9.62, \s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186\-2
344(Digital Signature Standard, \s-1DSS\s0)
345.SH "SEE ALSO"
346.IX Header "SEE ALSO"
347\&\fIdsa\fR\|(3), \fIrsa\fR\|(3)
348.SH "HISTORY"
349.IX Header "HISTORY"
350The ecdsa implementation was first introduced in OpenSSL 0.9.8
351.SH "AUTHOR"
352.IX Header "AUTHOR"
353Nils Larsch for the OpenSSL project (http://www.openssl.org).