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116 lines
4.6 KiB
C
116 lines
4.6 KiB
C
//-----------------------------------------------------------------------------
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// This code is licensed to you under the terms of the GNU GPL, version 2 or,
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// at your option, any later version. See the LICENSE.txt file for the text of
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// the license.
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//-----------------------------------------------------------------------------
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// Hitag2 Crypto
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//
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// (c) 2009 Henryk Plötz <henryk@ploetzli.ch>
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// (c) 2012 Roel Verdult
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// (c) 2019 Iceman
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//-----------------------------------------------------------------------------
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#include "hitag2_crypto.h"
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/* Following is a modified version of cryptolib.com/ciphers/hitag2/ */
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// Software optimized 48-bit Philips/NXP Mifare Hitag2 PCF7936/46/47/52 stream cipher algorithm by I.C. Wiener 2006-2007.
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// For educational purposes only.
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// No warranties or guarantees of any kind.
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// This code is released into the public domain by its author.
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// Single bit Hitag2 functions:
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#ifndef i4
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#define i4(x,a,b,c,d) ((uint32_t)((((x)>>(a))&1)+(((x)>>(b))&1)*2+(((x)>>(c))&1)*4+(((x)>>(d))&1)*8))
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#endif
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static const uint32_t ht2_f4a = 0x2C79; // 0010 1100 0111 1001
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static const uint32_t ht2_f4b = 0x6671; // 0110 0110 0111 0001
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static const uint32_t ht2_f5c = 0x7907287B; // 0111 1001 0000 0111 0010 1000 0111 1011
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uint32_t _f20(const uint64_t x) {
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uint32_t i5;
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i5 = ((ht2_f4a >> i4(x, 1, 2, 4, 5)) & 1) * 1
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+ ((ht2_f4b >> i4(x, 7, 11, 13, 14)) & 1) * 2
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+ ((ht2_f4b >> i4(x, 16, 20, 22, 25)) & 1) * 4
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+ ((ht2_f4b >> i4(x, 27, 28, 30, 32)) & 1) * 8
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+ ((ht2_f4a >> i4(x, 33, 42, 43, 45)) & 1) * 16;
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return (ht2_f5c >> i5) & 1;
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}
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uint64_t _hitag2_init(const uint64_t key, const uint32_t serial, const uint32_t IV) {
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uint32_t i;
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uint64_t x = ((key & 0xFFFF) << 32) + serial;
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for (i = 0; i < 32; i++) {
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x >>= 1;
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x += (uint64_t)(_f20(x) ^ (((IV >> i) ^ (key >> (i + 16))) & 1)) << 47;
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}
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return x;
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}
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uint64_t _hitag2_round(uint64_t *state) {
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uint64_t x = *state;
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x = (x >> 1) +
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((((x >> 0) ^ (x >> 2) ^ (x >> 3) ^ (x >> 6)
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^ (x >> 7) ^ (x >> 8) ^ (x >> 16) ^ (x >> 22)
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^ (x >> 23) ^ (x >> 26) ^ (x >> 30) ^ (x >> 41)
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^ (x >> 42) ^ (x >> 43) ^ (x >> 46) ^ (x >> 47)) & 1) << 47);
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*state = x;
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return _f20(x);
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}
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// "MIKRON" = O N M I K R
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// Key = 4F 4E 4D 49 4B 52 - Secret 48-bit key
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// Serial = 49 43 57 69 - Serial number of the tag, transmitted in clear
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// Random = 65 6E 45 72 - Random IV, transmitted in clear
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//~28~DC~80~31 = D7 23 7F CE - Authenticator value = inverted first 4 bytes of the keystream
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// The code below must print out "D7 23 7F CE 8C D0 37 A9 57 49 C1 E6 48 00 8A B6".
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// The inverse of the first 4 bytes is sent to the tag to authenticate.
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// The rest is encrypted by XORing it with the subsequent keystream.
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uint32_t _hitag2_byte(uint64_t *x) {
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uint32_t i, c;
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for (i = 0, c = 0; i < 8; i++) {
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c += (uint32_t) _hitag2_round(x) << (i ^ 7);
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}
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return c;
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}
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void hitag2_cipher_reset(struct hitag2_tag *tag, const uint8_t *iv) {
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uint64_t key = ((uint64_t)tag->sectors[2][2]) |
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((uint64_t)tag->sectors[2][3] << 8) |
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((uint64_t)tag->sectors[1][0] << 16) |
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((uint64_t)tag->sectors[1][1] << 24) |
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((uint64_t)tag->sectors[1][2] << 32) |
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((uint64_t)tag->sectors[1][3] << 40);
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uint32_t uid = ((uint32_t)tag->sectors[0][0]) |
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((uint32_t)tag->sectors[0][1] << 8) |
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((uint32_t)tag->sectors[0][2] << 16) |
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((uint32_t)tag->sectors[0][3] << 24);
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uint32_t iv_ = (((uint32_t)(iv[0]))) |
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(((uint32_t)(iv[1])) << 8) |
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(((uint32_t)(iv[2])) << 16) |
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(((uint32_t)(iv[3])) << 24);
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tag->cs = _hitag2_init(REV64(key), REV32(uid), REV32(iv_));
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}
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int hitag2_cipher_authenticate(uint64_t *cs, const uint8_t *authenticator_is) {
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uint8_t authenticator_should[4];
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authenticator_should[0] = ~_hitag2_byte(cs);
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authenticator_should[1] = ~_hitag2_byte(cs);
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authenticator_should[2] = ~_hitag2_byte(cs);
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authenticator_should[3] = ~_hitag2_byte(cs);
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return (memcmp(authenticator_should, authenticator_is, 4) == 0);
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}
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int hitag2_cipher_transcrypt(uint64_t *cs, uint8_t *data, uint16_t bytes, uint16_t bits) {
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int i;
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for (i = 0; i < bytes; i++) data[i] ^= _hitag2_byte(cs);
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for (i = 0; i < bits; i++) data[bytes] ^= _hitag2_round(cs) << (7 - i);
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return 0;
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}
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