Question

Short Question: Is there a proved strong reversible encryption method (in Python)?

Requirement: Do not require 3rd part of Python libraries.
Apply environment: transport data through networks.

I saw a method using str.translate() with a key-generated table. Here is the table generating function:

def get_table(key):
    m = hashlib.md5()
    m.update(key)
    s = m.digest()
    (a, b) = struct.unpack('<QQ', s)
    table = [c for c in string.maketrans('', '')]
    for i in xrange(1, 1024):
        table.sort(lambda x, y: int(a % (ord(x) + i) - a % (ord(y) + i)))
    return ''.join(table)

Questions about this function:

1. Is this a good/strong reversible encryption?
2. In the function 1024 is a big number, need we loop so many times to get a table that strong enough?

Thanks in advance.

Answer 1

If you want strong encryption without a third-party library, you’re out of luck–the Python Standard Library only has hash functions. If you want secure encryption you’ll have to either implement something like AES yourself (this is not a good idea, as it’s really easy for the inexperienced to mess up when implementing an encryption algorithm), or change your requirements and use PyCrypto.