incomplete attempt to implement bitfi's key derivation algorithm

bitfi.py

#!/usr/bin/env python

import sys
import hmac
import hashlib
import binascii

import scrypt
import pycoin
from pybitcointools import *

def mkd(password, salt):
    return scrypt.hash(password, salt, N=32768, p=4, r=8, buflen=64)

def ci(s):
    acc = ""
    for c in s.upper():
        acc += str(ord(c)-64)
    # XXX overflow behaviour is... questionable
    return int(acc)

def idx(s):
    return ci(s) | 0x8000000

def b2long(b):
    return long(binascii.hexlify(b), 16)

def masterkey(password, salt, coin):
    k_par = mkd(password, salt)
    c_par = hashlib.sha256(salt).digest()
    # XXX k_par and c_par may need to be swapped
    param = hmac.new(c_par, k_par, hashlib.sha512).digest()
    msk = param[0:32]
    mcc = param[32:64]
    xprv = bip32_serialize((PRIVATE, 0, b'\x00'*4, 0, mcc, msk+b'\x01'))
    print xprv
    print bip32_serialize((PRIVATE, 0, b'\x00'*4, idx(coin), mcc, msk+b'\x01'))
    return bip32_ckd(xprv, idx(coin))


p = sys.argv[1]
s = sys.argv[2]
c = sys.argv[3]

print masterkey(p, s, c)