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206 lines
5.9 KiB
206 lines
5.9 KiB
=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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