In [ ]:

    

import struct
import array
import os

def pack_neg(ID):
 type = 0
 id = ID
 data = struct.pack('>II', type, id)
 return data

def unpack_neg(data):
 type,id = struct.unpack('>II', data)
 return (type,id)

print "negotiation", unpack_neg(pack_neg(16))


def pack_init(clock, RAND, link_key):
  #clock - 26 bits, but lets send 32
  #RAND - 128 bit byte array
  #link key - 128 bit
  if len(RAND) != 16: 
    raise Exception("rand key not 128 bit") 
  if len(link_key) != 16:
    raise Exception("link key not 128 bit")

  type = 1
  data = struct.pack('>II', type, clock)
  r = array.array('B', RAND).tostring()
  l = array.array('B', link_key).tostring()
  return data + r + l

def unpack_init(data):
  d = struct.unpack('>II' + ('B' * 16) + ('B' * 16), data)
  type = d[0]
  clock = d[1]
  RAND = bytearray(d[2:18])
  link_key = bytearray(d[18:34])
  return (clock, RAND, link_key)

print "init", unpack_init(pack_init(20, bytearray(os.urandom(16)),bytearray(os.urandom(16))))


def pack_data(clock, data):
  type = 2  
  length = len(data)
  header = struct.pack('>III', type, clock, length)
  payload = array.array('B', data).tostring()
  d = header + payload
  return d

def unpack_data(data):
  print len(data)
  type, clock, length = struct.unpack('>III', data[:12])  
  d = struct.unpack('>' + ('B' * length), data[12:])
  d = bytearray(d)
  return (type,clock,length,d)
print unpack_data(pack_data(7, 'Hello'))