Efficient Python string obfuscation

Question

I need to obfuscate Unicode text lines to slow down those who can extract them. Ideally, this will be done using the Python built-in module or a small additional library; the length of the string will be the same or less than the original; and "unobfuscation" will be as fast as possible.

I tried various character substitutions and XOR routines, but they are slow. Base64 and hexadecimal encoding significantly increase the size. To date, the most efficient method I have found compresses zlib at the lowest setting (1). Is there a better way?

Answer 1

It uses a simple, fast encryption scheme for bytes objects.

 # For Python 3 - strings are Unicode, print is a function def obfuscate(byt): # Use same function in both directions. Input and output are bytes # objects. mask = b'keyword' lmask = len(mask) return bytes(c ^ mask[i % lmask] for i, c in enumerate(byt)) def test(s): data = obfuscate(s.encode()) print(len(s), len(data), data) newdata = obfuscate(data).decode() print(newdata == s) simple_string = 'Just plain ASCII' unicode_string = ('sensei = \N{HIRAGANA LETTER SE}\N{HIRAGANA LETTER N}' '\N{HIRAGANA LETTER SE}\N{HIRAGANA LETTER I}') test(simple_string) test(unicode_string) 

Python Version 2:

 # For Python 2 mask = 'keyword' nmask = [ord(c) for c in mask] lmask = len(mask) def obfuscate(s): # Use same function in both directions. Input and output are # Python 2 strings, ASCII only. return ''.join([chr(ord(c) ^ nmask[i % lmask]) for i, c in enumerate(s)]) def test(s): data = obfuscate(s.encode('utf-8')) print len(s), len(data), repr(data) newdata = obfuscate(data).decode('utf-8') print newdata == s simple_string = u'Just plain ASCII' unicode_string = (u'sensei = \N{HIRAGANA LETTER SE}\N{HIRAGANA LETTER N}' '\N{HIRAGANA LETTER SE}\N{HIRAGANA LETTER I}') test(simple_string) test(unicode_string) 

Answer 2

How about the old ROT13 stunt?

 >>> x = 'some string' >>> y = x.encode('rot13') >>> y 'fbzr fgevat' >>> y.decode('rot13') u'some string' 

For a Unicode string:

 >>> x = u'國碼' >>> print x國碼>>> y = x.encode('unicode-escape').encode('rot13') >>> print y \h570o\h78op >>> print y.decode('rot13').decode('unicode-escape')國碼