1Introduction & history
2======================
3
4Python-RSA's history starts in 2006. As a student assignment for the
5University of Amsterdam we wrote a RSA implementation. We chose Python
6for various reasons; one of the most important reasons was the
7`unlimited precision integer`_ support.
8
9.. _`unlimited precision integer`:
10    https://docs.python.org/3/library/stdtypes.html#numeric-types-int-float-complex
11
12It started out as just a module for calculating large primes, and RSA
13encryption, decryption, signing and verification using those large
14numbers. It also included generating public and private keys. There
15was no functionality for working with byte sequences (such as files)
16yet.
17
18Version 1.0 did include support for byte sequences, but quite clunky,
19mostly because it didn't support 0-bytes and thus was unsuitable for
20binary messages.
21
22Version 2.0 introduced a lot of improvements by Barry Mead, but still
23wasn't compatible with other RSA implementations and used no random
24padding.
25
26Version 3.0 introduced PKCS#1 v1.5 functionality, which resulted in
27compatibility with OpenSSL and many others implementing the same
28standard. Random padding was introduced that considerably increased
29security, which also resulted in the ability to encrypt and decrypt
30binary messages.
31
32Key generation was also improved in version 3.0, ensuring that you
33really get the number of bits you asked for. At the same time key
34generation speed was greatly improved. The ability to save and load
35public and private keys in PEM and DER format as also added.
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