Import OpenSSL-1.0.0g.
[dragonfly.git] / crypto / openssl / doc / crypto / ecdsa.pod
CommitLineData
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1=pod
2
3=head1 NAME
4
5ecdsa - Elliptic Curve Digital Signature Algorithm
6
7=head1 SYNOPSIS
8
9 #include <openssl/ecdsa.h>
10
11 ECDSA_SIG* ECDSA_SIG_new(void);
12 void ECDSA_SIG_free(ECDSA_SIG *sig);
13 int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
14 ECDSA_SIG* d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp,
15 long len);
16
17 ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
18 EC_KEY *eckey);
19 ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
20 const BIGNUM *kinv, const BIGNUM *rp,
21 EC_KEY *eckey);
22 int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
23 const ECDSA_SIG *sig, EC_KEY* eckey);
24 int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
25 BIGNUM **kinv, BIGNUM **rp);
26 int ECDSA_sign(int type, const unsigned char *dgst,
27 int dgstlen, unsigned char *sig,
28 unsigned int *siglen, EC_KEY *eckey);
29 int ECDSA_sign_ex(int type, const unsigned char *dgst,
30 int dgstlen, unsigned char *sig,
31 unsigned int *siglen, const BIGNUM *kinv,
32 const BIGNUM *rp, EC_KEY *eckey);
33 int ECDSA_verify(int type, const unsigned char *dgst,
34 int dgstlen, const unsigned char *sig,
35 int siglen, EC_KEY *eckey);
36 int ECDSA_size(const EC_KEY *eckey);
37
38 const ECDSA_METHOD* ECDSA_OpenSSL(void);
39 void ECDSA_set_default_method(const ECDSA_METHOD *meth);
40 const ECDSA_METHOD* ECDSA_get_default_method(void);
41 int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
42
43 int ECDSA_get_ex_new_index(long argl, void *argp,
44 CRYPTO_EX_new *new_func,
45 CRYPTO_EX_dup *dup_func,
46 CRYPTO_EX_free *free_func);
47 int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
48 void* ECDSA_get_ex_data(EC_KEY *d, int idx);
49
50=head1 DESCRIPTION
51
52The B<ECDSA_SIG> structure consists of two BIGNUMs for the
53r and s value of a ECDSA signature (see X9.62 or FIPS 186-2).
54
55 struct
56 {
57 BIGNUM *r;
58 BIGNUM *s;
59 } ECDSA_SIG;
60
61ECDSA_SIG_new() allocates a new B<ECDSA_SIG> structure (note: this
62function also allocates the BIGNUMs) and initialize it.
63
64ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>.
65
66i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature
67B<sig> and writes the encoded signature to B<*pp> (note: if B<pp>
68is NULL B<i2d_ECDSA_SIG> returns the expected length in bytes of
69the DER encoded signature). B<i2d_ECDSA_SIG> returns the length
70of the DER encoded signature (or 0 on error).
71
72d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns
73the decoded signature in a newly allocated B<ECDSA_SIG> structure.
74B<*sig> points to the buffer containing the DER encoded signature
75of size B<len>.
76
77ECDSA_size() returns the maximum length of a DER encoded
78ECDSA signature created with the private EC key B<eckey>.
79
80ECDSA_sign_setup() may be used to precompute parts of the
81signing operation. B<eckey> is the private EC key and B<ctx>
82is a pointer to B<BN_CTX> structure (or NULL). The precomputed
83values or returned in B<kinv> and B<rp> and can be used in a
84later call to B<ECDSA_sign_ex> or B<ECDSA_do_sign_ex>.
85
86ECDSA_sign() is wrapper function for ECDSA_sign_ex with B<kinv>
87and B<rp> set to NULL.
88
89ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes
90hash value B<dgst> using the private EC key B<eckey> and the optional
91pre-computed values B<kinv> and B<rp>. The DER encoded signatures is
92stored in B<sig> and it's length is returned in B<sig_len>. Note: B<sig>
93must point to B<ECDSA_size> bytes of memory. The parameter B<type>
94is ignored.
95
96ECDSA_verify() verifies that the signature in B<sig> of size
97B<siglen> is a valid ECDSA signature of the hash value
98value B<dgst> of size B<dgstlen> using the public key B<eckey>.
99The parameter B<type> is ignored.
100
101ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B<kinv>
102and B<rp> set to NULL.
103
104ECDSA_do_sign_ex() computes a digital signature of the B<dgst_len>
105bytes hash value B<dgst> using the private key B<eckey> and the
106optional pre-computed values B<kinv> and B<rp>. The signature is
107returned in a newly allocated B<ECDSA_SIG> structure (or NULL on error).
108
109ECDSA_do_verify() verifies that the signature B<sig> is a valid
110ECDSA signature of the hash value B<dgst> of size B<dgst_len>
111using the public key B<eckey>.
112
113=head1 RETURN VALUES
114
115ECDSA_size() returns the maximum length signature or 0 on error.
116
599e5fcd 117ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or 0
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118on error.
119
120ECDSA_verify() and ECDSA_do_verify() return 1 for a valid
121signature, 0 for an invalid signature and -1 on error.
122The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
123
124=head1 EXAMPLES
125
126Creating a ECDSA signature of given SHA-1 hash value using the
127named curve secp192k1.
128
129First step: create a EC_KEY object (note: this part is B<not> ECDSA
130specific)
131
132 int ret;
133 ECDSA_SIG *sig;
134 EC_KEY *eckey = EC_KEY_new();
135 if (eckey == NULL)
136 {
137 /* error */
138 }
139 key->group = EC_GROUP_new_by_nid(NID_secp192k1);
140 if (key->group == NULL)
141 {
142 /* error */
143 }
144 if (!EC_KEY_generate_key(eckey))
145 {
146 /* error */
147 }
148
149Second step: compute the ECDSA signature of a SHA-1 hash value
150using B<ECDSA_do_sign>
151
152 sig = ECDSA_do_sign(digest, 20, eckey);
153 if (sig == NULL)
154 {
155 /* error */
156 }
157
158or using B<ECDSA_sign>
159
160 unsigned char *buffer, *pp;
161 int buf_len;
162 buf_len = ECDSA_size(eckey);
163 buffer = OPENSSL_malloc(buf_len);
164 pp = buffer;
165 if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
166 {
167 /* error */
168 }
169
170Third step: verify the created ECDSA signature using B<ECDSA_do_verify>
171
172 ret = ECDSA_do_verify(digest, 20, sig, eckey);
173
174or using B<ECDSA_verify>
175
176 ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
177
178and finally evaluate the return value:
179
180 if (ret == -1)
181 {
182 /* error */
183 }
184 else if (ret == 0)
185 {
186 /* incorrect signature */
187 }
188 else /* ret == 1 */
189 {
190 /* signature ok */
191 }
192
193=head1 CONFORMING TO
194
195ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
196(Digital Signature Standard, DSS)
197
198=head1 SEE ALSO
199
200L<dsa(3)|dsa(3)>, L<rsa(3)|rsa(3)>
201
202=head1 HISTORY
203
204The ecdsa implementation was first introduced in OpenSSL 0.9.8
205
206=head1 AUTHOR
207
208Nils Larsch for the OpenSSL project (http://www.openssl.org).
209
210=cut