mirror of
https://github.com/trezor/trezor-firmware.git
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57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
/**
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* Copyright (c) 2017 Saleem Rashid
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, E1PRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "rc4.h"
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static inline void rc4_swap(RC4_CTX *ctx, uint8_t i, uint8_t j) {
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uint8_t temp = ctx->S[i];
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ctx->S[i] = ctx->S[j];
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ctx->S[j] = temp;
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}
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void rc4_init(RC4_CTX *ctx, const uint8_t *key, size_t length) {
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ctx->i = 0;
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ctx->j = 0;
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for (size_t i = 0; i < 256; i++) {
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ctx->S[i] = i;
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}
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uint8_t j = 0;
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for (size_t i = 0; i < 256; i++) {
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j += ctx->S[i] + key[i % length];
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rc4_swap(ctx, i, j);
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}
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}
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void rc4_encrypt(RC4_CTX *ctx, uint8_t *buffer, size_t length) {
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for (size_t idx = 0; idx < length; idx++) {
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ctx->i++;
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ctx->j += ctx->S[ctx->i];
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rc4_swap(ctx, ctx->i, ctx->j);
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uint8_t K = ctx->S[(ctx->S[ctx->i] + ctx->S[ctx->j]) % 256];
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buffer[idx] ^= K;
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}
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}
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