basex

Encoding/decoding of any given alphabet with any base using bitcoin style leading zero compression

This is a port of js base-x package from cryptocoinjs/base-x.

WARNING: This module is NOT RFC3548 compliant, it cannot be used for base16 (hex), base32, or base64 encoding in a standards compliant manner.

Example

Base58

from basex import basex

BASE58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
bs58 = basex(BASE58)

decoded = bs58.decode('5Kd3NBUAdUnhyzenEwVLy9pBKxSwXvE9FMPyR4UKZvpe6E3AgLr')

print(decoded)
# => bytearray(b'\x80\xed\xdb\xdc\x11h\xf1\xda\xea\xdb\xd3\xe4L\x1e?\x8fZ(L )\xf7\x8a\xd2j\xf9\x85\x83\xa4\x99\xde[\x19\x13\xa4\xf8c')

print(bs58.encode(decoded))
# => 5Kd3NBUAdUnhyzenEwVLy9pBKxSwXvE9FMPyR4UKZvpe6E3AgLr

Alphabets

See below for a list of commonly recognized alphabets, and their respective base.

Base	Alphabet
2	01
8	01234567
11	0123456789a
16	0123456789abcdef
32	0123456789ABCDEFGHJKMNPQRSTVWXYZ
32	ybndrfg8ejkmcpqxot1uwisza345h769 (z-base-32)
36	0123456789abcdefghijklmnopqrstuvwxyz
58	123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz
62	0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
64	ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
67	ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.!~

How it works

It encodes octet arrays by doing long divisions on all significant digits in the array, creating a representation of that number in the new base. Then for every leading zero in the input (not significant as a number) it will encode as a single leader character. This is the first in the alphabet and will decode as 8 bits. The other characters depend upon the base. For example, a base58 alphabet packs roughly 5.858 bits per character.

This means the encoded string 000f (using a base16, 0-f alphabet) will actually decode to 4 bytes unlike a canonical hex encoding which uniformly packs 4 bits into each character.

While unusual, this does mean that no padding is required and it works for bases like 43.

LICENSE MIT

A direct derivation of the base58 implementation from bitcoin/bitcoin, generalized for variable length alphabets.