BaseHash

BaseHash is a small library for creating reversible obfuscated identifier hashes to a given base and length. The project is based on the GO library, PseudoCrypt by Kevin Burns. The library is extendible to use custom alphabets and other bases.

The library uses golden primes and the Baillie-PSW primality test for hashing to n length. From testing, I have gotten base62 up to 171 in length.

Maximum number is Base^Length - 1.
-> 62^171 - 1 or 315485137315301582773830923281251564555089304044116975095028710
                 008180170985809814948409129256031320171601473029340987051144213
                 425607224233134700199050224309707192084206558324823774511143549
                 765069844412467187455459156942237963528166277256376429656681225
                 8180788198965409784329587392583208081351811265973977087

Encode

from basehash import base62

encoded = base62.encode(2013)
decoded = base62.decode('WT')

print encoded, decoded

WT 2013

Hash

from basehash import base62

hashed   = base62.hash(2013, 8)
unhashed = base62.unhash('6LhOma5b')

print hashed, unhashed

6LhOma5b 2013

Generating your own primes

The default primes are generated using the golden ratio, 1.618033988749894848 but this can be changed with basehash.base.GENERATOR

# Generate primes, default golden ratio.
GENERATOR = 1.618033988749894848 # Change to whatever you'd like

Maximum number while hashing

There is a maximum number while hashing with any given base. To find out what this number is, we use the Base^Length - 1 inside the base_maximum(length) method

from basehash import base36

print base36.maximum(12)

4738381338321616895

So with the max number for base36 at length 12 as 4738381338321616895 we get the following:

from basehash import base36

hash = base36.hash(4738381338321616895, 12)
# 'DR10828P4CZP'

hash = base36.hash(4738381338321616896, 12)
# ValueError: Number is too large for given length. Maximum is 36^12 - 1.

Extending

from basehash.base import *

ALPHA = tuple('24680ACEGIKMOQSUWYbdfhjlnprtvxz')

# Length 'base' is 31 -> len(ALPHA)

def encode(num):
    return base_encode(num, ALPHA)

def decode(key):
    return base_decode(key, ALPHA)

def hash(num, length=HASH_LENGTH):
    return base_hash(num, length, ALPHA)

def unhash(key):
    return base_unhash(key, ALPHA)

def maximum(length=HASH_LENGTH):
    return base_maximum(len(ALPHA), length)