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58 lines
1.8 KiB
C
58 lines
1.8 KiB
C
///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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#include "gsCommon.h"
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#include "gsRC4.h"
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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static void swap_byte (unsigned char *a, unsigned char *b)
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{
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unsigned char swapByte;
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swapByte = *a;
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*a = *b;
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*b = swapByte;
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}
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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void RC4Init(RC4Context *context, const unsigned char *key, int len)
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{
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int i=0;
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unsigned char stateIndex = 0;
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unsigned char keyIndex = 0;
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// must supply a key
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assert(key != NULL && len != 0);
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if (key == NULL || len == 0)
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return;
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context->x = 0;
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context->y = 0;
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for (i=0; i<256; i++)
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context->state[i] = (unsigned char)i;
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for (i=0; i<256; i++)
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{
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stateIndex = (unsigned char)(stateIndex + context->state[i] + key[keyIndex]);
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swap_byte(&context->state[i], &context->state[stateIndex]);
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keyIndex = (unsigned char)((keyIndex+1)%len);
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}
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}
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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void RC4Encrypt(RC4Context *context, const unsigned char *src, unsigned char *dest, int len)
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{
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int i = 0;
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for (i=0; i<len; i++)
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{
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context->x = (unsigned char)(context->x + 1); // ok to wrap around from overflow
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context->y = (unsigned char)(context->y + context->state[context->x]); // ditto
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swap_byte(&context->state[context->x], &context->state[context->y]);
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dest[i] = (unsigned char)(src[i] ^ context->state[(unsigned char)(context->state[context->x]+context->state[context->y])]);
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}
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}
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