| # Author: Trevor Perrin |
| # See the LICENSE file for legal information regarding use of this file. |
| |
| """Pure-Python RC4 implementation.""" |
| |
| from .rc4 import RC4 |
| from .cryptomath import * |
| |
| def new(key): |
| return Python_RC4(key) |
| |
| class Python_RC4(RC4): |
| def __init__(self, keyBytes): |
| RC4.__init__(self, keyBytes, "python") |
| S = [i for i in range(256)] |
| j = 0 |
| for i in range(256): |
| j = (j + S[i] + keyBytes[i % len(keyBytes)]) % 256 |
| S[i], S[j] = S[j], S[i] |
| |
| self.S = S |
| self.i = 0 |
| self.j = 0 |
| |
| def encrypt(self, plaintextBytes): |
| ciphertextBytes = plaintextBytes[:] |
| S = self.S |
| i = self.i |
| j = self.j |
| for x in range(len(ciphertextBytes)): |
| i = (i + 1) % 256 |
| j = (j + S[i]) % 256 |
| S[i], S[j] = S[j], S[i] |
| t = (S[i] + S[j]) % 256 |
| ciphertextBytes[x] ^= S[t] |
| self.i = i |
| self.j = j |
| return ciphertextBytes |
| |
| def decrypt(self, ciphertext): |
| return self.encrypt(ciphertext) |
