| 0,0 → 1,75 |
|---|
| """ crypto.cipher.wep |
| |
| The WEP encryption algorithm used in IEEE 802.11 |
| |
| Copyright © (c) 2002 by Paul A. Lambert |
| Read LICENSE.txt for license information. |
| |
| September 2002 |
| """ |
| from crypto.cipher.arc4 import ARC4 |
| from crypto.errors import IntegrityCheckError, BadKeySizeError |
| from zlib import crc32 |
| from struct import pack |
| |
| class WEP: |
| """ WEP Stream Cipher Algorithm |
| Automatically adds and removes IV and KeyId |
| """ |
| def __init__(self, key=None, keyId=None): |
| """ key -> octet string for key """ |
| self.name = 'WEP' |
| self.strength = None # depends on keySize |
| self.arc4 = ARC4() # base algorithm |
| self.__key = [None,None,None,None] # four possible keys, initialize to invalid keys |
| self.encryptHeaderSize = 4 |
| self.setCurrentKeyId(keyId) |
| if key != None: |
| self.setKey(key) |
| |
| def setKey(self, key, keyId=None): |
| """ Set key, key string is typically 5 or 13 octets long |
| """ |
| if not(len(key) in (5,13)): |
| raise BadKeySizeError,'Key not valid size of 5 or 13 octets' |
| if keyId != None : |
| self.setCurrentKeyId(keyId) |
| self.__key[self.currentKeyId] = key |
| self.keySize = len(key) |
| self.strength = self.keySize * 8 |
| |
| def setCurrentKeyId(self, keyId): |
| if keyId == None : |
| self.currentKeyId = 0 |
| elif (0<=keyId<4): |
| self.currentKeyId = keyId |
| else: |
| raise 'WEP keyId must be value 0, 1, 2 or 3' |
| |
| def encrypt(self, plainText, iv, keyId=None): |
| """ Encrypt a string and return a binary string |
| Adds WEP encryption header and crc |
| """ |
| assert(len(iv)==3),'Wrong size WEP IV' |
| if keyId != None : |
| self.setCurrentKeyId(keyId) |
| assert(self.__key[self.currentKeyId]!=None), 'Must set key for specific keyId before encryption' |
| self.arc4.setKey( iv + self.__key[self.currentKeyId] ) |
| crc = pack('<I',crc32(plainText)) |
| cipherText = self.arc4.encrypt(plainText+crc) |
| # add header that contains IV |
| cipherText = iv + chr((self.currentKeyId<<6)) + cipherText |
| return cipherText |
| |
| def decrypt(self, cipherText): |
| """ Decrypt a WEP packet, assumes WEP 4 byte header on packet """ |
| iv = cipherText[:3] |
| self.currentKeyId = (ord(cipherText[3])&0xC0)>>6 |
| assert(self.__key[self.currentKeyId]!=None), 'Must set key for specific keyId before encryption' |
| self.arc4.setKey( iv + self.__key[self.currentKeyId] ) |
| plainText = self.arc4.decrypt(cipherText[self.encryptHeaderSize:]) |
| if plainText[-self.encryptHeaderSize:] == pack('<I',crc32(plainText)): # check data integrity |
| raise IntegrityCheckError, 'WEP Integrity Check Error' |
| return plainText[:-4] |
| |
| |