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77 lines
2.0 KiB
C
77 lines
2.0 KiB
C
/*
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* ecc-cdh.c - One-Pass Diffie-Hellman method implementation
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* C(1, 1, ECC CDH) for EC DH of OpenPGP ECC
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*
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* Copyright (C) 2013 Free Software Initiative of Japan
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* Author: NIIBE Yutaka <gniibe@fsij.org>
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*
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* This file is a part of Gnuk, a GnuPG USB Token implementation.
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*
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* Gnuk is free software: you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Gnuk is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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* License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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/*
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* References:
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*
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* [1] A. Jivsov, Elliptic Curve Cryptography (ECC) in OpenPGP, RFC 6637,
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* June 2012.
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*
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* [2] Suite B Implementer's Guide to NIST SP 800-56A, July 28, 2009.
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*
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*/
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static const char param[] = {
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/**/
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curve_OID_len,
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curve_OID,
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public-key_alg_ID, /*ecdh*/
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0x03,
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0x01,
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KDF_hash_ID, /*sha256*/
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KEK_alg_ID, /*aes128*/
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"Anonymous Sender ",
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my_finger_print /*20-byte*/
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};
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/*
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*
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*/
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int
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ecdh (unsigned char *key,
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const unsigned char *key_encrypted, const ac *P,
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const naf4_257 *naf_d, const unsigned char *fp)
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{
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ac S[1];
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sha256_context ctx;
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unsigned char kek[32];
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unsigned char x[32];
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int i;
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const unsigned char *p;
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compute_kP (S, naf_d, P); /* Get shared secret. */
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/* Endian change from big to little. */
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p = (const unsigned char *)S->x;
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for (i = 0; i < 32; i++)
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x[31-i] = p[i];
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/* kdf (kek, S, parameter) */
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sha256_start (&ctx);
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sha256_update (&ctx, "\x00\x00\x00\x01", 4);
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sha256_update (&ctx, x, size of x);
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sha256_update (&ctx, (const char *)param, size of param);
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sha256_finish (&ctx, kek);
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}
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