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_SIG* ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
19 ECDSA_SIG* ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
20 const BIGNUM *kinv, const BIGNUM *rp,
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);
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);
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);
52 The B<ECDSA_SIG> structure consists of two BIGNUMs for the
53 r and s value of a ECDSA signature (see X9.62 or FIPS 186-2).
61 ECDSA_SIG_new() allocates a new B<ECDSA_SIG> structure (note: this
62 function also allocates the BIGNUMs) and initialize it.
64 ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>.
66 i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature
67 B<sig> and writes the encoded signature to B<*pp> (note: if B<pp>
68 is NULL B<i2d_ECDSA_SIG> returns the expected length in bytes of
69 the DER encoded signature). B<i2d_ECDSA_SIG> returns the length
70 of the DER encoded signature (or 0 on error).
72 d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns
73 the decoded signature in a newly allocated B<ECDSA_SIG> structure.
74 B<*sig> points to the buffer containing the DER encoded signature
77 ECDSA_size() returns the maximum length of a DER encoded
78 ECDSA signature created with the private EC key B<eckey>.
80 ECDSA_sign_setup() may be used to precompute parts of the
81 signing operation. B<eckey> is the private EC key and B<ctx>
82 is a pointer to B<BN_CTX> structure (or NULL). The precomputed
83 values or returned in B<kinv> and B<rp> and can be used in a
84 later call to B<ECDSA_sign_ex> or B<ECDSA_do_sign_ex>.
86 ECDSA_sign() is wrapper function for ECDSA_sign_ex with B<kinv>
87 and B<rp> set to NULL.
89 ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes
90 hash value B<dgst> using the private EC key B<eckey> and the optional
91 pre-computed values B<kinv> and B<rp>. The DER encoded signatures is
92 stored in B<sig> and it's length is returned in B<sig_len>. Note: B<sig>
93 must point to B<ECDSA_size> bytes of memory. The parameter B<type>
96 ECDSA_verify() verifies that the signature in B<sig> of size
97 B<siglen> is a valid ECDSA signature of the hash value
98 B<dgst> of size B<dgstlen> using the public key B<eckey>.
99 The parameter B<type> is ignored.
101 ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B<kinv>
102 and B<rp> set to NULL.
104 ECDSA_do_sign_ex() computes a digital signature of the B<dgst_len>
105 bytes hash value B<dgst> using the private key B<eckey> and the
106 optional pre-computed values B<kinv> and B<rp>. The signature is
107 returned in a newly allocated B<ECDSA_SIG> structure (or NULL on error).
109 ECDSA_do_verify() verifies that the signature B<sig> is a valid
110 ECDSA signature of the hash value B<dgst> of size B<dgst_len>
111 using the public key B<eckey>.
115 ECDSA_size() returns the maximum length signature or 0 on error.
117 ECDSA_sign_setup() and ECDSA_sign() return 1 if successful or 0
120 ECDSA_verify() and ECDSA_do_verify() return 1 for a valid
121 signature, 0 for an invalid signature and -1 on error.
122 The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
126 Creating a ECDSA signature of given SHA-1 hash value using the
127 named curve secp192k1.
129 First step: create a EC_KEY object (note: this part is B<not> ECDSA
135 eckey = EC_KEY_new_by_curve_name(NID_secp192k1);
140 if (!EC_KEY_generate_key(eckey))
145 Second step: compute the ECDSA signature of a SHA-1 hash value
146 using B<ECDSA_do_sign>
148 sig = ECDSA_do_sign(digest, 20, eckey);
154 or using B<ECDSA_sign>
156 unsigned char *buffer, *pp;
158 buf_len = ECDSA_size(eckey);
159 buffer = OPENSSL_malloc(buf_len);
161 if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
166 Third step: verify the created ECDSA signature using B<ECDSA_do_verify>
168 ret = ECDSA_do_verify(digest, 20, sig, eckey);
170 or using B<ECDSA_verify>
172 ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
174 and finally evaluate the return value:
182 /* incorrect signature */
191 ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
192 (Digital Signature Standard, DSS)
196 L<dsa(3)|dsa(3)>, L<rsa(3)|rsa(3)>
200 The ecdsa implementation was first introduced in OpenSSL 0.9.8
204 Nils Larsch for the OpenSSL project (http://www.openssl.org).