53934822ac
Files like dh.pod, etc., mostly duplicated the API-specific pod files. Removed the duplicated content; that often mean the whole file could be removed. Some of the content about internals got moved into README files in the source tree. Some content (e.g., err.pod) got moved into other pod pages. Annotate generic pages, remove dup NAME Reviewed-by: Richard Levitte <levitte@openssl.org>
197 lines
7 KiB
Text
197 lines
7 KiB
Text
=pod
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=head1 NAME
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ECDSA_SIG_new, ECDSA_SIG_free, i2d_ECDSA_SIG, d2i_ECDSA_SIG, ECDSA_size,
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ECDSA_sign, ECDSA_do_sign, ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup,
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ECDSA_sign_ex, ECDSA_do_sign_ex - low level elliptic curve digital signature
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algorithm (ECDSA) functions
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=head1 SYNOPSIS
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#include <openssl/ecdsa.h>
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ECDSA_SIG *ECDSA_SIG_new(void);
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void ECDSA_SIG_free(ECDSA_SIG *sig);
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void ECDSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const ECDSA_SIG *sig);
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int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
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ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len);
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int ECDSA_size(const EC_KEY *eckey);
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int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen,
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unsigned char *sig, unsigned int *siglen, EC_KEY *eckey);
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ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len,
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EC_KEY *eckey);
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int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen,
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const unsigned char *sig, int siglen, EC_KEY *eckey);
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int ECDSA_do_verify(const unsigned char *dgst, int dgst_len,
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const ECDSA_SIG *sig, EC_KEY* eckey);
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ECDSA_SIG *ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen,
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const BIGNUM *kinv, const BIGNUM *rp,
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EC_KEY *eckey);
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int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp);
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int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen,
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unsigned char *sig, unsigned int *siglen,
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const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey);
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=head1 DESCRIPTION
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Note: these functions provide a low level interface to ECDSA. Most
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applications should use the higher level B<EVP> interface such as
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L<EVP_DigestSignInit(3)> or L<EVP_DigestVerifyInit(3)> instead.
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B<ECDSA_SIG> is an opaque structure consisting of two BIGNUMs for the
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B<r> and B<s> value of an ECDSA signature (see X9.62 or FIPS 186-2).
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ECDSA_SIG_new() allocates a new B<ECDSA_SIG> structure (note: this
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function also allocates the BIGNUMs) and initializes it.
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ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>.
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ECDSA_SIG_get0() returns internal pointers the B<r> and B<s> values contained
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in B<sig>. The values can then be examined or initialised.
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i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature B<sig> and
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writes the encoded signature to B<*pp> (note: if B<pp> is NULL i2d_ECDSA_SIG()
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returns the expected length in bytes of the DER encoded signature).
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i2d_ECDSA_SIG() returns the length of the DER encoded signature (or 0 on
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error).
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d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns the decoded
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signature in a newly allocated B<ECDSA_SIG> structure. B<*sig> points to the
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buffer containing the DER encoded signature of size B<len>.
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ECDSA_size() returns the maximum length of a DER encoded ECDSA signature
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created with the private EC key B<eckey>.
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ECDSA_sign() computes a digital signature of the B<dgstlen> bytes hash value
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B<dgst> using the private EC key B<eckey>. The DER encoded signatures is
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stored in B<sig> and it's length is returned in B<sig_len>. Note: B<sig> must
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point to ECDSA_size(eckey) bytes of memory. The parameter B<type> is currently
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ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with B<kinv>
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and B<rp> set to NULL.
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ECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned
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as a newly allocated B<ECDSA_SIG> structure (or NULL on error). ECDSA_do_sign()
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is a wrapper function for ECDSA_do_sign_ex() with B<kinv> and B<rp> set to
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NULL.
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ECDSA_verify() verifies that the signature in B<sig> of size B<siglen> is a
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valid ECDSA signature of the hash value B<dgst> of size B<dgstlen> using the
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public key B<eckey>. The parameter B<type> is ignored.
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ECDSA_do_verify() is similar to ECDSA_verify() except the signature is
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presented in the form of a pointer to an B<ECDSA_SIG> structure.
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The remaining functions utilise the internal B<kinv> and B<r> values used
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during signature computation. Most applications will never need to call these
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and some external ECDSA ENGINE implementations may not support them at all if
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either B<kinv> or B<r> is not B<NULL>.
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ECDSA_sign_setup() may be used to precompute parts of the signing operation.
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B<eckey> is the private EC key and B<ctx> is a pointer to B<BN_CTX> structure
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(or NULL). The precomputed values or returned in B<kinv> and B<rp> and can be
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used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex().
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ECDSA_sign_ex() computes a digital signature of the B<dgstlen> bytes hash value
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B<dgst> using the private EC key B<eckey> and the optional pre-computed values
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B<kinv> and B<rp>. The DER encoded signatures is stored in B<sig> and it's
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length is returned in B<sig_len>. Note: B<sig> must point to ECDSA_size(eckey)
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bytes of memory. The parameter B<type> is ignored.
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ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is
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returned as a newly allocated B<ECDSA_SIG> structure (or NULL on error).
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=head1 RETURN VALUES
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ECDSA_size() returns the maximum length signature or 0 on error.
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ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful
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or 0 on error.
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ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated
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B<ECDSA_SIG> structure or NULL on error.
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ECDSA_verify() and ECDSA_do_verify() return 1 for a valid
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signature, 0 for an invalid signature and -1 on error.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 EXAMPLES
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Creating an ECDSA signature of a given SHA-256 hash value using the
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named curve prime256v1 (aka P-256).
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First step: create an EC_KEY object (note: this part is B<not> ECDSA
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specific)
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int ret;
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ECDSA_SIG *sig;
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EC_KEY *eckey;
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eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
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if (eckey == NULL) {
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/* error */
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}
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if (EC_KEY_generate_key(eckey) == 0) {
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/* error */
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}
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Second step: compute the ECDSA signature of a SHA-256 hash value
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using ECDSA_do_sign():
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sig = ECDSA_do_sign(digest, 32, eckey);
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if (sig == NULL) {
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/* error */
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}
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or using ECDSA_sign():
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unsigned char *buffer, *pp;
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int buf_len;
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buf_len = ECDSA_size(eckey);
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buffer = OPENSSL_malloc(buf_len);
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pp = buffer;
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if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0) {
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/* error */
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}
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Third step: verify the created ECDSA signature using ECDSA_do_verify():
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ret = ECDSA_do_verify(digest, 32, sig, eckey);
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or using ECDSA_verify():
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ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey);
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and finally evaluate the return value:
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if (ret == 1) {
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/* signature ok */
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} else if (ret == 0) {
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/* incorrect signature */
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} else {
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/* error */
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}
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=head1 CONFORMING TO
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ANSI X9.62, US Federal Information Processing Standard FIPS 186-2
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(Digital Signature Standard, DSS)
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=head1 SEE ALSO
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L<dsa(3)>,
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L<EVP_DigestSignInit(3)>,
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L<EVP_DigestVerifyInit(3)>
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=head1 COPYRIGHT
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Copyright 2004-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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