ecdsa(3) OpenSSL ecdsa(3) NNAAMMEE ECDSA_SIG_new, ECDSA_SIG_free, i2d_ECDSA_SIG, d2i_ECDSA_SIG, ECDSA_size, ECDSA_sign_setup, ECDSA_sign, ECDSA_sign_ex, ECDSA_verify, ECDSA_do_sign, ECDSA_do_sign_ex, ECDSA_do_verify - Elliptic Curve Digi- tal Signature Algorithm SSYYNNOOPPSSIISS #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); DDEESSCCRRIIPPTTIIOONN 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 func- tion 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 signa- ture 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 oper- ation. 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 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-com- puted values kkiinnvv and rrpp. The signature is returned in a newly allo- cated 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 sig- nature of the hash value ddggsstt of size ddggsstt__lleenn using the public key eecckkeeyy. RREETTUURRNN VVAALLUUEESS _E_C_D_S_A___S_I_G___n_e_w_(_) returns NULL if the allocation fails. _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 0 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). EEXXAAMMPPLLEESS 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 spe- cific) int ret; ECDSA_SIG *sig; EC_KEY *eckey; eckey = EC_KEY_new_by_curve_name(NID_secp192k1); if (eckey == 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 */ } CCOONNFFOORRMMIINNGG TTOO ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 (Dig- ital Signature Standard, DSS) SSEEEE AALLSSOO _d_s_a(3), _r_s_a(3) HHIISSTTOORRYY The ecdsa implementation was first introduced in OpenSSL 0.9.8 AAUUTTHHOORR Nils Larsch for the OpenSSL project (http://www.openssl.org). 1.0.2u 2019-12-20 ecdsa(3)