1. Introduction & history

Python-RSA’s history starts in 2006. As a student assignment for the University of Amsterdam we wrote a RSA implementation. We chose Python for various reasons; one of the most important reasons was the unlimited precision integer support.

It started out as just a module for calculating large primes, and RSA encryption, decryption, signing and verification using those large numbers. It also included generating public and private keys. There was no functionality for working with byte sequences (such as files) yet.

Version 1.0 did include support for byte sequences, but quite clunky, mostly because it didn’t support 0-bytes and thus was unsuitable for binary messages.

Version 2.0 introduced a lot of improvements by Barry Mead, but still wasn’t compatible with other RSA implementations and used no random padding.

Version 3.0 introduced PKCS#1 v1.5 functionality, which resulted in compatibility with OpenSSL and many others implementing the same standard. Random padding was introduced that considerably increased security, which also resulted in the ability to encrypt and decrypt binary messages.

Key generation was also improved in version 3.0, ensuring that you really get the number of bits you asked for. At the same time key generation speed was greatly improved. The ability to save and load public and private keys in PEM and DER format as also added.