faset over fra Z3950 til google books

python/gdata/tlslite/utils/Python_RC4.py

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+"""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, key):
+        RC4.__init__(self, key, "python")
+        keyBytes = stringToBytes(key)
+        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, plaintext):
+        plaintextBytes = stringToBytes(plaintext)
+        S = self.S
+        i = self.i
+        j = self.j
+        for x in range(len(plaintextBytes)):
+            i = (i + 1) % 256
+            j = (j + S[i]) % 256
+            S[i], S[j] = S[j], S[i]
+            t = (S[i] + S[j]) % 256
+            plaintextBytes[x] ^= S[t]
+        self.i = i
+        self.j = j
+        return bytesToString(plaintextBytes)
+
+    def decrypt(self, ciphertext):
+        return self.encrypt(ciphertext)