206 lines
5.9 KiB
Text
206 lines
5.9 KiB
Text
=pod
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=head1 NAME
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ecdsa - Elliptic Curve Digital Signature Algorithm
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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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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,
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long len);
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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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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_do_verify(const unsigned char *dgst, int dgst_len,
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const ECDSA_SIG *sig, EC_KEY* eckey);
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int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx,
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BIGNUM **kinv, BIGNUM **rp);
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int ECDSA_sign(int type, const unsigned char *dgst,
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int dgstlen, unsigned char *sig,
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unsigned int *siglen, EC_KEY *eckey);
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int ECDSA_sign_ex(int type, const unsigned char *dgst,
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int dgstlen, unsigned char *sig,
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unsigned int *siglen, const BIGNUM *kinv,
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const BIGNUM *rp, EC_KEY *eckey);
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int ECDSA_verify(int type, const unsigned char *dgst,
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int dgstlen, const unsigned char *sig,
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int siglen, EC_KEY *eckey);
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int ECDSA_size(const EC_KEY *eckey);
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const ECDSA_METHOD* ECDSA_OpenSSL(void);
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void ECDSA_set_default_method(const ECDSA_METHOD *meth);
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const ECDSA_METHOD* ECDSA_get_default_method(void);
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int ECDSA_set_method(EC_KEY *eckey,const ECDSA_METHOD *meth);
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int ECDSA_get_ex_new_index(long argl, void *argp,
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CRYPTO_EX_new *new_func,
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CRYPTO_EX_dup *dup_func,
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CRYPTO_EX_free *free_func);
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int ECDSA_set_ex_data(EC_KEY *d, int idx, void *arg);
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void* ECDSA_get_ex_data(EC_KEY *d, int idx);
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=head1 DESCRIPTION
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The B<ECDSA_SIG> structure consists of two BIGNUMs for the
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r and s value of a ECDSA signature (see X9.62 or FIPS 186-2).
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struct
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{
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BIGNUM *r;
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BIGNUM *s;
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} ECDSA_SIG;
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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 initialize it.
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ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>.
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i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature
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B<sig> and writes the encoded signature to B<*pp> (note: if B<pp>
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is NULL B<i2d_ECDSA_SIG> returns the expected length in bytes of
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the DER encoded signature). B<i2d_ECDSA_SIG> returns the length
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of the DER encoded signature (or 0 on error).
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d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns
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the decoded signature in a newly allocated B<ECDSA_SIG> structure.
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B<*sig> points to the buffer containing the DER encoded signature
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of size B<len>.
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ECDSA_size() returns the maximum length of a DER encoded
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ECDSA signature created with the private EC key B<eckey>.
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ECDSA_sign_setup() may be used to precompute parts of the
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signing operation. B<eckey> is the private EC key and B<ctx>
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is a pointer to B<BN_CTX> structure (or NULL). The precomputed
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values or returned in B<kinv> and B<rp> and can be used in a
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later call to B<ECDSA_sign_ex> or B<ECDSA_do_sign_ex>.
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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_sign_ex() computes a digital signature of the B<dgstlen> bytes
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hash value B<dgst> using the private EC key B<eckey> and the optional
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pre-computed values B<kinv> and B<rp>. 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>
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must point to B<ECDSA_size> bytes of memory. The parameter B<type>
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is ignored.
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ECDSA_verify() verifies that the signature in B<sig> of size
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B<siglen> is a valid ECDSA signature of the hash value
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B<dgst> of size B<dgstlen> using the public key B<eckey>.
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The parameter B<type> is ignored.
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ECDSA_do_sign() is wrapper function for ECDSA_do_sign_ex with B<kinv>
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and B<rp> set to NULL.
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ECDSA_do_sign_ex() computes a digital signature of the B<dgst_len>
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bytes hash value B<dgst> using the private key B<eckey> and the
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optional pre-computed values B<kinv> and B<rp>. The signature is
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returned in a newly allocated B<ECDSA_SIG> structure (or NULL on error).
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ECDSA_do_verify() verifies that the signature B<sig> is a valid
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ECDSA signature of the hash value B<dgst> of size B<dgst_len>
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using the public key B<eckey>.
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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_setup() and ECDSA_sign() return 1 if successful or 0
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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)|ERR_get_error(3)>.
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=head1 EXAMPLES
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Creating a ECDSA signature of given SHA-1 hash value using the
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named curve secp192k1.
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First step: create a 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_secp192k1);
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if (eckey == NULL)
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{
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/* error */
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}
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if (!EC_KEY_generate_key(eckey))
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{
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/* error */
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}
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Second step: compute the ECDSA signature of a SHA-1 hash value
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using B<ECDSA_do_sign>
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sig = ECDSA_do_sign(digest, 20, eckey);
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if (sig == NULL)
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{
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/* error */
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}
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or using B<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);
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{
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/* error */
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}
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Third step: verify the created ECDSA signature using B<ECDSA_do_verify>
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ret = ECDSA_do_verify(digest, 20, sig, eckey);
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or using B<ECDSA_verify>
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ret = ECDSA_verify(0, digest, 20, 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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{
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/* error */
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}
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else if (ret == 0)
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{
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/* incorrect signature */
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}
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else /* ret == 1 */
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{
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/* signature ok */
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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)|dsa(3)>, L<rsa(3)|rsa(3)>
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=head1 HISTORY
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The ecdsa implementation was first introduced in OpenSSL 0.9.8
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=head1 AUTHOR
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Nils Larsch for the OpenSSL project (http://www.openssl.org).
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=cut
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