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https://github.com/RfidResearchGroup/proxmark3.git
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64 lines
1.8 KiB
C
64 lines
1.8 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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// Generic TEA crypto code.
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// ref: http://143.53.36.235:8080/source.htm#ansi
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//-----------------------------------------------------------------------------
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#include "tea.h"
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#define ROUNDS 32
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#define DELTA 0x9E3779B9
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#define SUM 0xC6EF3720
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void tea_encrypt(uint8_t *v, uint8_t *key) {
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uint32_t a = 0, b = 0, c = 0, d = 0, y = 0, z = 0;
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uint32_t sum = 0;
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uint8_t n = ROUNDS;
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//key
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a = bytes_to_num(key, 4);
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b = bytes_to_num(key + 4, 4);
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c = bytes_to_num(key + 8, 4);
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d = bytes_to_num(key + 12, 4);
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//input
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y = bytes_to_num(v, 4);
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z = bytes_to_num(v + 4, 4);
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while (n-- > 0) {
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sum += DELTA;
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y += ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
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z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
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}
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num_to_bytes(y, 4, v);
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num_to_bytes(z, 4, v + 4);
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}
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void tea_decrypt(uint8_t *v, uint8_t *key) {
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uint32_t a = 0, b = 0, c = 0, d = 0, y = 0, z = 0;
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uint32_t sum = SUM;
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uint8_t n = ROUNDS;
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//key
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a = bytes_to_num(key, 4);
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b = bytes_to_num(key + 4, 4);
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c = bytes_to_num(key + 8, 4);
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d = bytes_to_num(key + 12, 4);
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//input
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y = bytes_to_num(v, 4);
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z = bytes_to_num(v + 4, 4);
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/* sum = delta<<5, in general sum = delta * n */
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while (n-- > 0) {
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z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
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y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
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sum -= DELTA;
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}
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num_to_bytes(y, 4, v);
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num_to_bytes(z, 4, v + 4);
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}
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