Skip to content
Pure Python Paillier Homomorphic Cryptosystem
Python
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
paillier Add setup.py and create paillier package Nov 13, 2014
tests Plaintext constant addition and multiplication Aug 18, 2011
.gitignore Initial commit Aug 8, 2011
LICENSE Initial commit Aug 8, 2011
README.md Add setup.py and create paillier package Nov 13, 2014
demo.py
requirements.txt Initial commit Aug 8, 2011
setup.py Add setup.py and create paillier package Nov 13, 2014

README.md

Pure Python Paillier Homomorphic Cryptosystem

This is a very basic pure Python implementation of the Paillier Homomorphic Cryptosystem.

Homomorphic Cryptosystems

The idea of homomorphic computation is to encrypt some numbers, perform algebraic operations like "add" and "multiply" on cyphertexts, then decrypt the result and find it to be exactly the same as if corresponding "+" and "*" operations were applied to the plaintexts.

In other words, a homomorphic cryptosystem enables cryptographically secure computations in an untrusted environment.

Paillier cryptosystem

Paillier cryptosystem is a probabilistic asymmetric algorithm for public key cryptography. Paillier cryptosystem is partially homomorphic as it can only add encrypted numbers or multiply an encrypted number by an unencrypted multiplier.

Implementation

This pure Python implementation exploits Python's long type with its arbitrary precision arithmetics. Public key is serializable, thus it can be pickled along with the encrypted numbers and sent to a remote server for computation.

The code is loosely based on Thep and a few ActiveState recipes.

Please note that this implementation's primary purpose is education; it is not suitable for production use as it is.

Installation and Tests

The paillier.py module has no external dependencies besides included primes.py. Simply run demo.py to see it in action.

To run unit tests please install Nose:

$ pip install -r requirements.txt
$ nosetests
...............
Ran 814 tests in 11.544s
OK

Usage

$ ipython
Python 2.7.1 (r271:86832, Jun 16 2011, 16:59:05)
Type "copyright", "credits" or "license" for more information.

In [1]: from paillier.paillier import *

In [2]: priv, pub = generate_keypair(128)

In [3]: x = encrypt(pub, 2)

In [4]: y = encrypt(pub, 3)

In [5]: x,y
Out[5]:
(72109737005643982735171545918..., 9615446835366886883470187...)

In [6]: z = e_add(pub, x, y)

In [7]: z
Out[7]: 71624230283745591274688669...

In [8]: decrypt(priv, pub, z)
Out[8]: 5L

License and Copyright

LGPL v3, see LICENSE

(C) 2011 Mike Ivanov

You can’t perform that action at this time.