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Title "ECDSA_SIG_NEW 3"
way too many mistakes in technical documents.
\fB\s-1ECDSA_SIG\s0 is an opaque structure consisting of two BIGNUMs for the \fBr and s value of an \s-1ECDSA\s0 signature (see X9.62 or \s-1FIPS 186-2\s0).
\fBECDSA_SIG_new() allocates an empty \s-1ECDSA_SIG\s0 structure. Note: before OpenSSL 1.1.0 the: the r and s components were initialised.
\fBECDSA_SIG_free() frees the \s-1ECDSA_SIG\s0 structure sig.
\fBECDSA_SIG_get0() returns internal pointers the r and s values contained in sig and stores them in *pr and *ps, respectively. The pointer pr or ps can be \s-1NULL,\s0 in which case the corresponding value is not returned.
The values r, s can also be retrieved separately by the corresponding function ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively.
The r and s values can be set by calling ECDSA_SIG_set0() and passing the new values for r and s as parameters to the function. Calling this function transfers the memory management of the values to the \s-1ECDSA_SIG\s0 object, and therefore the values that have been passed in should not be freed directly after this function has been called.
See i2d_ECDSA_SIG\|(3) and d2i_ECDSA_SIG\|(3) for information about encoding and decoding \s-1ECDSA\s0 signatures to/from \s-1DER.\s0
\fBECDSA_size() returns the maximum length of a \s-1DER\s0 encoded \s-1ECDSA\s0 signature created with the private \s-1EC\s0 key eckey.
\fBECDSA_sign() computes a digital signature of the dgstlen bytes hash value \fBdgst using the private \s-1EC\s0 key eckey. The \s-1DER\s0 encoded signatures is stored in sig and its length is returned in sig_len. Note: sig must point to ECDSA_size(eckey) bytes of memory. The parameter type is currently ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with kinv and rp set to \s-1NULL.\s0
\fBECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned as a newly allocated \s-1ECDSA_SIG\s0 structure (or \s-1NULL\s0 on error). ECDSA_do_sign() is a wrapper function for ECDSA_do_sign_ex() with kinv and rp set to \s-1NULL.\s0
\fBECDSA_verify() verifies that the signature in sig of size siglen is a valid \s-1ECDSA\s0 signature of the hash value dgst of size dgstlen using the public key eckey. The parameter type is ignored.
\fBECDSA_do_verify() is similar to ECDSA_verify() except the signature is presented in the form of a pointer to an \s-1ECDSA_SIG\s0 structure.
The remaining functions utilise the internal kinv and r values used during signature computation. Most applications will never need to call these and some external \s-1ECDSA ENGINE\s0 implementations may not support them at all if either kinv or r is not \s-1NULL\s0.
\fBECDSA_sign_setup() may be used to precompute parts of the signing operation. \fBeckey is the private \s-1EC\s0 key and ctx is a pointer to \s-1BN_CTX\s0 structure (or \s-1NULL\s0). The precomputed values or returned in kinv and rp and can be used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex().
\fBECDSA_sign_ex() computes a digital signature of the dgstlen bytes hash value \fBdgst using the private \s-1EC\s0 key eckey and the optional pre-computed values \fBkinv and rp. The \s-1DER\s0 encoded signature is stored in sig and its length is returned in sig_len. Note: sig must point to ECDSA_size(eckey) bytes of memory. The parameter type is ignored.
\fBECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is returned as a newly allocated \s-1ECDSA_SIG\s0 structure (or \s-1NULL\s0 on error).
\fBECDSA_SIG_set0() returns 1 on success or 0 on failure.
\fBECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, or \s-1NULL\s0 if it is unset.
\fBECDSA_size() returns the maximum length signature or 0 on error.
\fBECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful or 0 on error.
\fBECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated \fB\s-1ECDSA_SIG\s0 structure or \s-1NULL\s0 on error.
\fBECDSA_verify() and ECDSA_do_verify() return 1 for a valid signature, 0 for an invalid signature and -1 on error. The error codes can be obtained by ERR_get_error\|(3).
First step: create an \s-1EC_KEY\s0 object (note: this part is not \s-1ECDSA\s0 specific)
.Vb 3 int ret; ECDSA_SIG *sig; EC_KEY *eckey; \& eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1); if (eckey == NULL) /* error */ if (EC_KEY_generate_key(eckey) == 0) /* error */ .Ve
Second step: compute the \s-1ECDSA\s0 signature of a \s-1SHA-256\s0 hash value using ECDSA_do_sign():
.Vb 3 sig = ECDSA_do_sign(digest, 32, eckey); if (sig == NULL) /* error */ .Ve
or using ECDSA_sign():
.Vb 2 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) == 0) /* error */ .Ve
Third step: verify the created \s-1ECDSA\s0 signature using ECDSA_do_verify():
.Vb 1 ret = ECDSA_do_verify(digest, 32, sig, eckey); .Ve
or using ECDSA_verify():
.Vb 1 ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey); .Ve
and finally evaluate the return value:
.Vb 6 if (ret == 1) /* signature ok */ else if (ret == 0) /* incorrect signature */ else /* error */ .Ve
Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.