Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / ecdsa.3
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124.\" ========================================================================
125.\"
126.IX Title "ecdsa 3"
e3261593 127.TH ecdsa 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
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132.SH "NAME"
133ecdsa \- Elliptic Curve Digital Signature Algorithm
134.SH "SYNOPSIS"
135.IX Header "SYNOPSIS"
136.Vb 1
137\& #include <openssl/ecdsa.h>
e257b235 138\&
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139\& ECDSA_SIG* ECDSA_SIG_new(void);
140\& void ECDSA_SIG_free(ECDSA_SIG *sig);
141\& int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
142\& ECDSA_SIG* d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp,
143\& long len);
e257b235 144\&
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145\& ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
146\& EC_KEY *eckey);
147\& ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
148\& const BIGNUM *kinv, const BIGNUM *rp,
149\& EC_KEY *eckey);
150\& int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
151\& const ECDSA_SIG *sig, EC_KEY* eckey);
152\& int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
153\& BIGNUM **kinv, BIGNUM **rp);
154\& int ECDSA_sign(int type, const unsigned char *dgst,
155\& int dgstlen, unsigned char *sig,
156\& unsigned int *siglen, EC_KEY *eckey);
157\& int ECDSA_sign_ex(int type, const unsigned char *dgst,
158\& int dgstlen, unsigned char *sig,
159\& unsigned int *siglen, const BIGNUM *kinv,
160\& const BIGNUM *rp, EC_KEY *eckey);
161\& int ECDSA_verify(int type, const unsigned char *dgst,
162\& int dgstlen, const unsigned char *sig,
163\& int siglen, EC_KEY *eckey);
164\& int ECDSA_size(const EC_KEY *eckey);
e257b235 165\&
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166\& const ECDSA_METHOD* ECDSA_OpenSSL(void);
167\& void ECDSA_set_default_method(const ECDSA_METHOD *meth);
168\& const ECDSA_METHOD* ECDSA_get_default_method(void);
169\& int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
e257b235 170\&
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171\& int ECDSA_get_ex_new_index(long argl, void *argp,
172\& CRYPTO_EX_new *new_func,
173\& CRYPTO_EX_dup *dup_func,
174\& CRYPTO_EX_free *free_func);
175\& int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
176\& void* ECDSA_get_ex_data(EC_KEY *d, int idx);
177.Ve
178.SH "DESCRIPTION"
179.IX Header "DESCRIPTION"
180The \fB\s-1ECDSA_SIG\s0\fR structure consists of two BIGNUMs for the
181r and s value of a \s-1ECDSA\s0 signature (see X9.62 or \s-1FIPS\s0 186\-2).
182.PP
183.Vb 5
184\& struct
185\& {
186\& BIGNUM *r;
187\& BIGNUM *s;
188\& } ECDSA_SIG;
189.Ve
190.PP
191\&\fIECDSA_SIG_new()\fR allocates a new \fB\s-1ECDSA_SIG\s0\fR structure (note: this
192function also allocates the BIGNUMs) and initialize it.
193.PP
194\&\fIECDSA_SIG_free()\fR frees the \fB\s-1ECDSA_SIG\s0\fR structure \fBsig\fR.
195.PP
196\&\fIi2d_ECDSA_SIG()\fR creates the \s-1DER\s0 encoding of the \s-1ECDSA\s0 signature
197\&\fBsig\fR and writes the encoded signature to \fB*pp\fR (note: if \fBpp\fR
198is \s-1NULL\s0 \fBi2d_ECDSA_SIG\fR returns the expected length in bytes of
199the \s-1DER\s0 encoded signature). \fBi2d_ECDSA_SIG\fR returns the length
200of the \s-1DER\s0 encoded signature (or 0 on error).
201.PP
202\&\fId2i_ECDSA_SIG()\fR decodes a \s-1DER\s0 encoded \s-1ECDSA\s0 signature and returns
203the decoded signature in a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure.
204\&\fB*sig\fR points to the buffer containing the \s-1DER\s0 encoded signature
205of size \fBlen\fR.
206.PP
207\&\fIECDSA_size()\fR returns the maximum length of a \s-1DER\s0 encoded
208\&\s-1ECDSA\s0 signature created with the private \s-1EC\s0 key \fBeckey\fR.
209.PP
210\&\fIECDSA_sign_setup()\fR may be used to precompute parts of the
211signing operation. \fBeckey\fR is the private \s-1EC\s0 key and \fBctx\fR
212is a pointer to \fB\s-1BN_CTX\s0\fR structure (or \s-1NULL\s0). The precomputed
213values or returned in \fBkinv\fR and \fBrp\fR and can be used in a
214later call to \fBECDSA_sign_ex\fR or \fBECDSA_do_sign_ex\fR.
215.PP
216\&\fIECDSA_sign()\fR is wrapper function for ECDSA_sign_ex with \fBkinv\fR
217and \fBrp\fR set to \s-1NULL\s0.
218.PP
219\&\fIECDSA_sign_ex()\fR computes a digital signature of the \fBdgstlen\fR bytes
220hash value \fBdgst\fR using the private \s-1EC\s0 key \fBeckey\fR and the optional
221pre-computed values \fBkinv\fR and \fBrp\fR. The \s-1DER\s0 encoded signatures is
222stored in \fBsig\fR and it's length is returned in \fBsig_len\fR. Note: \fBsig\fR
223must point to \fBECDSA_size\fR bytes of memory. The parameter \fBtype\fR
224is ignored.
225.PP
226\&\fIECDSA_verify()\fR verifies that the signature in \fBsig\fR of size
227\&\fBsiglen\fR is a valid \s-1ECDSA\s0 signature of the hash value
228value \fBdgst\fR of size \fBdgstlen\fR using the public key \fBeckey\fR.
229The parameter \fBtype\fR is ignored.
230.PP
231\&\fIECDSA_do_sign()\fR is wrapper function for ECDSA_do_sign_ex with \fBkinv\fR
232and \fBrp\fR set to \s-1NULL\s0.
233.PP
234\&\fIECDSA_do_sign_ex()\fR computes a digital signature of the \fBdgst_len\fR
235bytes hash value \fBdgst\fR using the private key \fBeckey\fR and the
236optional pre-computed values \fBkinv\fR and \fBrp\fR. The signature is
237returned in a newly allocated \fB\s-1ECDSA_SIG\s0\fR structure (or \s-1NULL\s0 on error).
238.PP
239\&\fIECDSA_do_verify()\fR verifies that the signature \fBsig\fR is a valid
240\&\s-1ECDSA\s0 signature of the hash value \fBdgst\fR of size \fBdgst_len\fR
241using the public key \fBeckey\fR.
242.SH "RETURN VALUES"
243.IX Header "RETURN VALUES"
244\&\fIECDSA_size()\fR returns the maximum length signature or 0 on error.
245.PP
246\&\fIECDSA_sign_setup()\fR and \fIECDSA_sign()\fR return 1 if successful or \-1
247on error.
248.PP
249\&\fIECDSA_verify()\fR and \fIECDSA_do_verify()\fR return 1 for a valid
250signature, 0 for an invalid signature and \-1 on error.
251The error codes can be obtained by \fIERR_get_error\fR\|(3).
252.SH "EXAMPLES"
253.IX Header "EXAMPLES"
254Creating a \s-1ECDSA\s0 signature of given \s-1SHA\-1\s0 hash value using the
255named curve secp192k1.
256.PP
257First step: create a \s-1EC_KEY\s0 object (note: this part is \fBnot\fR \s-1ECDSA\s0
258specific)
259.PP
e257b235 260.Vb 10
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261\& int ret;
262\& ECDSA_SIG *sig;
263\& EC_KEY *eckey = EC_KEY_new();
264\& if (eckey == NULL)
265\& {
266\& /* error */
267\& }
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268\& key\->group = EC_GROUP_new_by_nid(NID_secp192k1);
269\& if (key\->group == NULL)
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270\& {
271\& /* error */
272\& }
273\& if (!EC_KEY_generate_key(eckey))
274\& {
275\& /* error */
276\& }
277.Ve
278.PP
279Second step: compute the \s-1ECDSA\s0 signature of a \s-1SHA\-1\s0 hash value
e257b235 280using \fBECDSA_do_sign\fR
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281.PP
282.Vb 5
283\& sig = ECDSA_do_sign(digest, 20, eckey);
284\& if (sig == NULL)
285\& {
286\& /* error */
287\& }
288.Ve
289.PP
290or using \fBECDSA_sign\fR
291.PP
292.Vb 9
293\& unsigned char *buffer, *pp;
294\& int buf_len;
295\& buf_len = ECDSA_size(eckey);
296\& buffer = OPENSSL_malloc(buf_len);
297\& pp = buffer;
298\& if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
299\& {
300\& /* error */
301\& }
302.Ve
303.PP
304Third step: verify the created \s-1ECDSA\s0 signature using \fBECDSA_do_verify\fR
305.PP
306.Vb 1
307\& ret = ECDSA_do_verify(digest, 20, sig, eckey);
308.Ve
309.PP
310or using \fBECDSA_verify\fR
311.PP
312.Vb 1
313\& ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
314.Ve
315.PP
316and finally evaluate the return value:
317.PP
318.Vb 12
e257b235 319\& if (ret == \-1)
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320\& {
321\& /* error */
322\& }
323\& else if (ret == 0)
324\& {
325\& /* incorrect signature */
326\& }
327\& else /* ret == 1 */
328\& {
329\& /* signature ok */
330\& }
331.Ve
332.SH "CONFORMING TO"
333.IX Header "CONFORMING TO"
334\&\s-1ANSI\s0 X9.62, \s-1US\s0 Federal Information Processing Standard \s-1FIPS\s0 186\-2
335(Digital Signature Standard, \s-1DSS\s0)
336.SH "SEE ALSO"
337.IX Header "SEE ALSO"
338\&\fIdsa\fR\|(3), \fIrsa\fR\|(3)
339.SH "HISTORY"
340.IX Header "HISTORY"
341The ecdsa implementation was first introduced in OpenSSL 0.9.8
342.SH "AUTHOR"
343.IX Header "AUTHOR"
344Nils Larsch for the OpenSSL project (http://www.openssl.org).