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rc4: Initial commit
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/** | ||
* Copyright (c) 2017 Saleem Rashid | ||
* | ||
* Permission is hereby granted, free of charge, to any person obtaining | ||
* a copy of this software and associated documentation files (the "Software"), | ||
* to deal in the Software without restriction, including without limitation | ||
* the rights to use, copy, modify, merge, publish, distribute, sublicense, | ||
* and/or sell copies of the Software, and to permit persons to whom the | ||
* Software is furnished to do so, subject to the following conditions: | ||
* | ||
* The above copyright notice and this permission notice shall be included | ||
* in all copies or substantial portions of the Software. | ||
* | ||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, E1PRESS | ||
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | ||
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES | ||
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, | ||
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR | ||
* OTHER DEALINGS IN THE SOFTWARE. | ||
*/ | ||
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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) { | ||
uint8_t temp = ctx->S[i]; | ||
ctx->S[i] = ctx->S[j]; | ||
ctx->S[j] = temp; | ||
} | ||
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void rc4_init(RC4_CTX *ctx, const uint8_t *key, size_t length) { | ||
ctx->i = 0; | ||
ctx->j = 0; | ||
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for (size_t i = 0; i < 256; i++) { | ||
ctx->S[i] = i; | ||
} | ||
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uint8_t j = 0; | ||
for (size_t i = 0; i < 256; i++) { | ||
j += ctx->S[i] + key[i % length]; | ||
rc4_swap(ctx, i, j); | ||
} | ||
} | ||
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void rc4_encrypt(RC4_CTX *ctx, uint8_t *buffer, size_t length) { | ||
for (size_t idx = 0; idx < length; idx++) { | ||
ctx->i++; | ||
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]; | ||
buffer[idx] ^= K; | ||
} | ||
} |
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/** | ||
* Copyright (c) 2017 Saleem Rashid | ||
* | ||
* Permission is hereby granted, free of charge, to any person obtaining | ||
* a copy of this software and associated documentation files (the "Software"), | ||
* to deal in the Software without restriction, including without limitation | ||
* the rights to use, copy, modify, merge, publish, distribute, sublicense, | ||
* and/or sell copies of the Software, and to permit persons to whom the | ||
* Software is furnished to do so, subject to the following conditions: | ||
* | ||
* The above copyright notice and this permission notice shall be included | ||
* in all copies or substantial portions of the Software. | ||
* | ||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS | ||
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | ||
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES | ||
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, | ||
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR | ||
* OTHER DEALINGS IN THE SOFTWARE. | ||
*/ | ||
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#ifndef __RC4_H__ | ||
#define __RC4_H__ | ||
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#include <stdint.h> | ||
#include <stddef.h> | ||
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typedef struct { | ||
uint8_t S[256]; | ||
uint8_t i, j; | ||
} RC4_CTX; | ||
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void rc4_init(RC4_CTX *ctx, const uint8_t *key, size_t length); | ||
void rc4_encrypt(RC4_CTX *ctx, uint8_t *buffer, size_t length); | ||
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#endif |