5 ecdsa - Elliptic Curve Digital Signature Algorithm
9 #include <openssl/ecdsa.h>
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,
17 ECDSA_DATA* ECDSA_DATA_new(void);
18 ECDSA_DATA* ECDSA_DATA_new_method(ENGINE *eng);
19 void ECDSA_DATA_free(ECDSA_DATA *data);
20 ECDSA_DATA* ecdsa_check(EC_KEY *eckey);
22 ECDSA_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
24 int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
25 ECDSA_SIG *sig, EC_KEY* eckey);
26 int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
27 BIGNUM **kinv, BIGNUM **rp);
28 int ECDSA_sign(int type, const unsigned char *dgst,
29 int dgstlen, unsigned char *sig,
30 unsigned int *siglen, EC_KEY *eckey);
31 int ECDSA_verify(int type, const unsigned char *dgst,
32 int dgstlen, const unsigned char *sig,
33 int siglen, EC_KEY *eckey);
34 int ECDSA_size(const EC_KEY *eckey);
36 const ECDSA_METHOD* ECDSA_OpenSSL(void);
37 void ECDSA_set_default_method(const ECDSA_METHOD *meth);
38 const ECDSA_METHOD* ECDSA_get_default_method(void);
39 int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
41 int ECDSA_get_ex_new_index(long argl, void *argp,
42 CRYPTO_EX_new *new_func,
43 CRYPTO_EX_dup *dup_func,
44 CRYPTO_EX_free *free_func);
45 int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
46 void* ECDSA_get_ex_data(EC_KEY *d, int idx);
50 The B<ECDSA_SIG> structure consists of two BIGNUMs for the
51 r and s value of a ECDSA signature (see X9.62 or FIPS 186-2).
59 ECDSA_SIG_new() allocates a new B<ECDSA_SIG> structure (note: this
60 function also allocates the BIGNUMs) and initialize it.
62 ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>.
64 i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature
65 B<sig> and writes the encoded signature to B<*pp> (note: if B<pp>
66 is NULL B<i2d_ECDSA_SIG> returns the expected length in bytes of
67 the DER encoded signature). B<i2d_ECDSA_SIG> returns the length
68 of the DER encoded signature (or 0 on error).
70 d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns
71 the decoded signature in a newly allocated B<ECDSA_SIG> structure.
72 B<*sig> points to the buffer containing the DER encoded signature
75 The B<ECDSA_DATA> structure extends the B<EC_KEY_METH_DATA>
76 structure with ECDSA specific data.
80 /* EC_KEY_METH_DATA part */
81 int (*init)(EC_KEY *);
82 void (*finish)(EC_KEY *);
83 /* method (ECDSA) specific part */
84 BIGNUM *kinv; /* signing pre-calc */
85 BIGNUM *r; /* signing pre-calc */
90 B<kinv> and B<r> are used to store precomputed values (see
93 ECDSA_DATA_new() returns a newly allocated and initialized
94 B<ECDSA_DATA> structure (or NULL on error).
96 ECDSA_DATA_free() frees the B<ECDSA_DATA> structure B<data>.
98 ecdsa_check() returns the pointer to the B<ECDSA_DATA>
99 structure in B<EC_KEY-E<gt>meth_data> (if B<EC_KEY-E<gt>meth_data>
100 is not a pointer to a B<ECDSA_DATA> structure then the old
101 data is freed and a new B<ECDSA_DATA> structure is allocated
102 using B<ECDSA_DATA_new>).
104 ECDSA_size() returns the maximum length of a DER encoded
105 ECDSA signature created with the private EC key B<eckey>.
107 ECDSA_sign_setup() may be used to precompute parts of the
108 signing operation. B<eckey> is the private EC key and B<ctx>
109 is a pointer to B<BN_CTX> structure (or NULL). The precomputed
110 values or returned in B<kinv> and B<rp> and can be used in a
111 later call to B<ECDSA_sign> or B<ECDSA_do_sign> when placed in
112 B<ECDSA_DATA-E<gt>kinv> and B<ECDSA_DATA-E<gt>r>.
114 ECDSA_sign() computes a digital signature of the B<dgstlen> bytes
115 hash value B<dgst> using the private EC key B<eckey> and places
116 the DER encoding of the created signature in B<sig>. The length
117 of the created signature is returned in B<sig_len>. Note: B<sig>
118 must point to B<ECDSA_size> bytes of memory. The parameter B<type>
121 ECDSA_verify() verifies that the signature in B<sig> of size
122 B<siglen> is a valid ECDSA signature of the hash value
123 value B<dgst> of size B<dgstlen> using the public key B<eckey>.
124 The parameter B<type> is ignored.
126 ECDSA_do_sign() computes a digital signature of the B<dgst_len>
127 bytes hash value B<dgst> using the private key B<eckey> and
128 returns the signature in a newly allocated B<ECDSA_SIG> structure
131 ECDSA_do_verify() verifies that the signature B<sig> is a valid
132 ECDSA signature of the hash value B<dgst> of size B<dgst_len>
133 using the public key B<eckey>.
137 ECDSA_size() returns the maximum length signature or 0 on error.
139 ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or -1
142 ECDSA_verify() and ECDSA_do_verify() return 1 for a valid
143 signature, 0 for an invalid signature and -1 on error.
144 The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
148 Creating a ECDSA signature of given SHA-1 hash value using the
149 named curve secp192k1.
151 First step: create a EC_KEY object (note: this part is B<not> ECDSA
156 EC_KEY *eckey = EC_KEY_new();
161 key->group = EC_GROUP_new_by_nid(NID_secp192k1);
162 if (key->group == NULL)
166 if (!EC_KEY_generate_key(eckey))
171 Second step: compute the ECDSA signature of a SHA-1 hash value
172 using B<ECDSA_do_sign>
174 sig = ECDSA_do_sign(digest, 20, eckey);
180 or using B<ECDSA_sign>
182 unsigned char *buffer, *pp;
184 buf_len = ECDSA_size(eckey);
185 buffer = OPENSSL_malloc(buf_len);
187 if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
192 Third step: verify the created ECDSA signature using B<ECDSA_do_verify>
194 ret = ECDSA_do_verify(digest, 20, sig, eckey);
196 or using B<ECDSA_verify>
198 ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
200 and finally evaluate the return value:
208 /* incorrect signature */
217 ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
218 (Digital Signature Standard, DSS)
222 L<dsa(3)|dsa(3)>, L<rsa(3)|rsa(3)>
226 The ecdsa implementation was first introduced in OpenSSL 0.9.8
230 Nils Larsch for the OpenSSL project (http://www.openssl.org).