ecdsa 3 2005-11-24 0.9.9-dev OpenSSL

NAME

ecdsa - Elliptic Curve Digital Signature Algorithm

LIBRARY

libcrypto, -lcrypto

SYNOPSIS


 #include 


 ECDSA_SIG*     ECDSA_SIG_new(void);
 void           ECDSA_SIG_free(ECDSA_SIG *sig);
 int            i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
 ECDSA_SIG*     d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp,
                long len);




 ECDSA_SIG*     ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
                        EC_KEY *eckey);
 ECDSA_SIG*     ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
                        const BIGNUM *kinv, const BIGNUM *rp,
                        EC_KEY *eckey);
 int            ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
                        const ECDSA_SIG *sig, EC_KEY* eckey);
 int            ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
                        BIGNUM **kinv, BIGNUM **rp);
 int            ECDSA_sign(int type, const unsigned char *dgst,
                        int dgstlen, unsigned char *sig,
                        unsigned int *siglen, EC_KEY *eckey);
 int            ECDSA_sign_ex(int type, const unsigned char *dgst,
                        int dgstlen, unsigned char *sig,
                        unsigned int *siglen, const BIGNUM *kinv,
                        const BIGNUM *rp, EC_KEY *eckey);
 int            ECDSA_verify(int type, const unsigned char *dgst,
                        int dgstlen, const unsigned char *sig,
                        int siglen, EC_KEY *eckey);
 int            ECDSA_size(const EC_KEY *eckey);


 const ECDSA_METHOD*    ECDSA_OpenSSL(void);
 void           ECDSA_set_default_method(const ECDSA_METHOD *meth);
 const ECDSA_METHOD*    ECDSA_get_default_method(void);
 int            ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);






 int            ECDSA_get_ex_new_index(long argl, void *argp,
                        CRYPTO_EX_new *new_func,
                        CRYPTO_EX_dup *dup_func,
                        CRYPTO_EX_free *free_func);
 int            ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
 void*          ECDSA_get_ex_data(EC_KEY *d, int idx);

DESCRIPTION

The EECCDDSSAA__SSIIGG structure consists of two BIGNUMs for the r and s value of a ECDSA signature (see X9.62 or FIPS 186-2).


 struct
        {
        BIGNUM *r;
        BIGNUM *s;
 } ECDSA_SIG;

_E_C_D_S_A___S_I_G___n_e_w_(_) allocates a new EECCDDSSAA__SSIIGG structure (note: this function also allocates the BIGNUMs) and initialize it.

_E_C_D_S_A___S_I_G___f_r_e_e_(_) frees the EECCDDSSAA__SSIIGG structure ssiigg.

_i_2_d___E_C_D_S_A___S_I_G_(_) creates the DER encoding of the ECDSA signature ssiigg and writes the encoded signature to **pppp (note: if pppp is NULL ii22dd__EECCDDSSAA__SSIIGG returns the expected length in bytes of the DER encoded signature). ii22dd__EECCDDSSAA__SSIIGG returns the length of the DER encoded signature (or 0 on error).

_d_2_i___E_C_D_S_A___S_I_G_(_) decodes a DER encoded ECDSA signature and returns the decoded signature in a newly allocated EECCDDSSAA__SSIIGG structure. **ssiigg points to the buffer containing the DER encoded signature of size lleenn.

_E_C_D_S_A___s_i_z_e_(_) returns the maximum length of a DER encoded ECDSA signature created with the private EC key eecckkeeyy.

_E_C_D_S_A___s_i_g_n___s_e_t_u_p_(_) may be used to precompute parts of the signing operation. eecckkeeyy is the private EC key and ccttxx is a pointer to BBNN__CCTTXX structure (or NULL). The precomputed values or returned in kkiinnvv and rrpp and can be used in a later call to EECCDDSSAA__ssiiggnn__eexx or EECCDDSSAA__ddoo__ssiiggnn__eexx.

_E_C_D_S_A___s_i_g_n_(_) is wrapper function for ECDSA_sign_ex with kkiinnvv and rrpp set to NULL.

_E_C_D_S_A___s_i_g_n___e_x_(_) computes a digital signature of the ddggssttlleenn bytes hash value ddggsstt using the private EC key eecckkeeyy and the optional pre-computed values kkiinnvv and rrpp. The DER encoded signatures is stored in ssiigg and it's length is returned in ssiigg__lleenn. Note: ssiigg must point to EECCDDSSAA__ssiizzee bytes of memory. The parameter ttyyppee is ignored.

_E_C_D_S_A___v_e_r_i_f_y_(_) verifies that the signature in ssiigg of size ssiigglleenn is a valid ECDSA signature of the hash value value ddggsstt of size ddggssttlleenn using the public key eecckkeeyy. The parameter ttyyppee is ignored.

_E_C_D_S_A___d_o___s_i_g_n_(_) is wrapper function for ECDSA_do_sign_ex with kkiinnvv and rrpp set to NULL.

_E_C_D_S_A___d_o___s_i_g_n___e_x_(_) computes a digital signature of the ddggsstt__lleenn bytes hash value ddggsstt using the private key eecckkeeyy and the optional pre-computed values kkiinnvv and rrpp. The signature is returned in a newly allocated EECCDDSSAA__SSIIGG structure (or NULL on error).

_E_C_D_S_A___d_o___v_e_r_i_f_y_(_) verifies that the signature ssiigg is a valid ECDSA signature of the hash value ddggsstt of size ddggsstt__lleenn using the public key eecckkeeyy.

RETURN VALUES

_E_C_D_S_A___s_i_z_e_(_) returns the maximum length signature or 0 on error.

_E_C_D_S_A___s_i_g_n___s_e_t_u_p_(_) and _E_C_D_S_A___s_i_g_n_(_) return 1 if successful or -1 on error.

_E_C_D_S_A___v_e_r_i_f_y_(_) and _E_C_D_S_A___d_o___v_e_r_i_f_y_(_) return 1 for a valid signature, 0 for an invalid signature and -1 on error. The error codes can be obtained by _E_R_R___g_e_t___e_r_r_o_r(3).

EXAMPLES

Creating a ECDSA signature of given SHA-1 hash value using the named curve secp192k1.

First step: create a EC_KEY object (note: this part is nnoott ECDSA specific)



 int        ret;
 ECDSA_SIG *sig;
 EC_KEY    *eckey = EC_KEY_new();
 if (eckey == NULL)
        {
        /* error */
        }
 key->group = EC_GROUP_new_by_nid(NID_secp192k1);
 if (key->group == NULL)
        {
        /* error */
        }
 if (!EC_KEY_generate_key(eckey))
        {
        /* error */
        }

Second step: compute the ECDSA signature of a SHA-1 hash value using EECCDDSSAA__ddoo__ssiiggnn



 sig = ECDSA_do_sign(digest, 20, eckey);
 if (sig == NULL)
        {
        /* error */
        }

or using EECCDDSSAA__ssiiggnn



 unsigned char *buffer, *pp;
 int            buf_len;
 buf_len = ECDSA_size(eckey);
 buffer  = OPENSSL_malloc(buf_len);
 pp = buffer;
 if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey);
        {
        /* error */
        }

Third step: verify the created ECDSA signature using EECCDDSSAA__ddoo__vveerriiffyy


 ret = ECDSA_do_verify(digest, 20, sig, eckey);

or using EECCDDSSAA__vveerriiffyy


 ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);

and finally evaluate the return value:



 if (ret == -1)
        {
        /* error */
        }
 else if (ret == 0)
        {
        /* incorrect signature */
        }
 else   /* ret == 1 */
        {
        /* signature ok */
        }

CONFORMING TO

ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 (Digital Signature Standard, DSS)

SEE ALSO

_o_p_e_n_s_s_l___d_s_a(3), _o_p_e_n_s_s_l___r_s_a(3)

HISTORY

The ecdsa implementation was first introduced in OpenSSL 0.9.8

AUTHOR

Nils Larsch for the OpenSSL project (http://www.openssl.org).