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//
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// License:
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// https://github.com/rapid7/metasploit-framework/blob/master/LICENSE
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//
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// This code was originally obtained and modified from the following source
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// by Bobin Verton:
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// https://gist.github.com/rverton/a44fc8ca67ab9ec32089
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#define N 256   // 2^8
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void swap(unsigned char *a, unsigned char *b) {
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  int tmp = *a;
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  *a = *b;
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  *b = tmp;
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}
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int KSA(char *key, unsigned char *S) {
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  int len = strlen(key);
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  int j = 0;
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  for (int i = 0; i < N; i++) {
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    S[i] = i;
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  }
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  for (int i = 0; i < N; i++) {
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    j = (j + S[i] + key[i % len]) % N;
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    swap(&S[i], &S[j]);
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  }
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  return 0;
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}
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int PRGA(unsigned char *S, char *plaintext, unsigned char *ciphertext, int plainTextSize) {
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  int i = 0;
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  int j = 0;
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  for (size_t n = 0, len = plainTextSize; n < len; n++) {
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    i = (i + 1) % N;
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    j = (j + S[i]) % N;
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    swap(&S[i], &S[j]);
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    int rnd = S[(S[i] + S[j]) % N];
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    ciphertext[n] = rnd ^ plaintext[n];
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  }
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  return 0;
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}
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int RC4(char *key, char *plaintext, unsigned char *ciphertext, int plainTextSize) {
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  unsigned char S[N];
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  KSA(key, S);
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  PRGA(S, plaintext, ciphertext, plainTextSize);
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  return 0;
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}
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