pprp 0.2.0

Overview

This package was a remedy to there being no PyPI-published, pure-Python Rijndael (AES) implementations, and that nothing available, in general, was compatible with both Python2 and Python3. The same is true of the PBKDF2 key-expansion algorithm.

The encrypter expects a source generator (which yields individual blocks). The encrypter and decrypter functions are written as generators. Decrypted data has PKCS7 padding. A utility function is provided to trim this (trim_pkcs7_padding).

The implementation includes Python2 and Python3 implementations of both Rijndael and PBKDF2, and chooses the version when loaded.

This project is also referred to as pprp, which stands for “Pure Python Rijndael and PBKDF2”.

Installation

Install via pip:

$ sudo pip install pprp

Example

Encrypt and decrypt the data, and compare the results. This example works in both Python 2 and 3.

Top imports and defines:

import io
import os.path
import hashlib

import pprp

# Make the strings the right type for the current Python version.
def trans(text):
    return text.encode('ASCII') if sys.version_info[0] >= 3 else text

passphrase = trans('password')
salt = trans('salt')
block_size = 16
key_size = 32
data = "this is a test" * 100

Do the key-expansion:

key = pprp.pbkdf2(passphrase, salt, key_size)

Define the source generator (we’ll give this to the encrypter):

def source_gen():
    for i in range(0, len(data), block_size):
        block = data[i:i + block_size]
        len_ = len(block)

        if len_ > 0:
            yield block.encode('ASCII')

        if len_ < block_size:
            break

Connect the encryptor to the decryptor:

encrypted_gen = pprp.rjindael_encrypt_gen(key, source_gen(), block_size)

Run, sink the output into an IO stream, and trim the padding off the last block:

s = io.BytesIO()
ends_at = 0
for block in pprp.rjindael_decrypt_gen(key, encrypted_gen, block_size):
    ends_at += block_size
    if ends_at >= len(data):
        block = pprp.trim_pkcs7_padding(block)

    s.write(block)

decrypted = s.getvalue()

Check the result:

assert data == decrypted.decode('ASCII')