• Multiply Two Big Numbers

• Modular Arithmetic

• Euclid's super algorithm

Here is a set of RSA cryptosystem tools.

• Get RSA Key Information
• Encrypt or Decrypt RSA messages
• RSA 129
  The historic RSA challenge from 1977.

• Get a Fiat-Shamir certificate
  for playing the square root game.
• Get some Random Numbers
  for playing the square root game. Get at least six sets.
• Get your prize
  by playing the square root game. You have to register your public key and get some random numbers before playing.

• Frequency Counts
  • Single Letter Frequencies
  • Block Frequencies
  • A sample text for counts.

• Caesar Ciphers

• Affine Ciphers

• MonoAlphabetic Ciphers
  • Chap. 1, Exercise 20 text

• Vigenere Ciphers
  • Chap. 2, Exercise 5 text
  • Chap. 2, Exercise 6 text
  • Leibniz quote
  • Minihan (NSA) quote 1
  • Minihan quote 2

• Crack a Vigenere Cipher!
  • Use Kasiski's method to find key length
  • Use Friedman's method to find key length
  • Count a subsequence of the text
  • Keyword guesser

• Enigma Machine in Java by Andy Carlson

• Shift Sequences