| 0,0 → 1,69 |
|---|
| """ crypto.keyedHash.michael |
| |
| A reference implementation of the Michael Message Integrety Chek (MIC) |
| that is defined in IEEE 802.11 Task Group 'i' |
| |
| Michael is a 64-bit MIC, with a design strength of 20 bits. |
| |
| Copyright © (c) 2002 by Paul A. Lambert |
| Read LICENSE.txt for license information. |
| """ |
| from struct import pack, unpack |
| from binascii_plus import * |
| |
| class Michael: |
| """ The Michael keyed hash as defined in IEEE 802.11i D2.0 """ |
| def __init__(self, key = None): |
| self.name = 'Michael' |
| self.blocksize = 1 # single octets can be hashed by padding to raw block size |
| self.raw_block_size = 4 # operates on 32 bits or 4 byte blocks |
| self.digest_size = 8 # MIC size of 64 bits or 8 bytes |
| self.keySize = 8 # key size is 8 octets |
| self.strength = 20 |
| if key != None: |
| self.setKey(key) |
| |
| def __del__(self): |
| self.setKey(8*chr(0)) # feable attempt to clear keys on exit |
| |
| def setKey(self,key): |
| """ setKey(key) ... key is binary string """ |
| assert( len(key)== self.keySize), 'Key must be 8 octets' |
| self._key = unpack('<II', key) # unpack into 2 32bit integers |
| |
| def __call__(self,data,more=None): |
| return self.hash(data) |
| |
| def hash(self,data): |
| """ Michael keyed hash """ |
| fullBlocks, extraOctets = divmod(len(data),4) |
| paddedData = data + chr(0x5a) + chr(0)*(7-extraOctets) |
| l, r = self._key |
| for i in range(fullBlocks+2): |
| mSub_i = unpack('<I', paddedData[i*4:i*4+4])[0] # ith block as 32 bit integer |
| l = l ^ mSub_i |
| l, r = b(l,r) |
| digest = pack('<II', l, r ) |
| return digest |
| |
| def update(self,data): |
| raise 'No update method supported for Michael keyed hash' |
| def digest(self): |
| raise 'No digest method supported for Michael keyed hash' |
| def final(self,data): |
| raise 'No final method supported for Michael keyed hash' |
| |
| def b(l,r): |
| """ The 'b' block function for the IEEE 802.11i Michael Integrity Check """ |
| r ^= (((l<<17) & 0xffffffffL)|((l>>15) & 0x1ffffL)) # r = r ^ (l <<< 17) |
| l = (l+r) & 0xffffffffL # l = (l+r) mod 2**32 |
| r ^= ((l & 0xff00ff00L)>>8)|((l & 0x00ff00ffL)<<8) # r = r ^ XSWAP(l) |
| l = (l+r) & 0xffffffffL # l = (l+r) mod 2**32 |
| r ^= (((l<<3) & 0xffffffffL) | ((l>>29)& 0x7)) # r = r ^ (l <<< 3) |
| l = (l+r) & 0xffffffffL # l = (l+r) mod 2**32 |
| r ^= (((l<<30L) & 0xffffffffL)|((l>>2) & 0x3fffffff)) # r = r ^ (l >>> 2) |
| l = (l+r) & 0xffffffffL # l = (l+r) mod 2**32 |
| return (l,r) |
| |
| |
| |