- RSA
- RSA cryptography is a popular asymmetric key cryptosystem, used in the famous PGP email program. I first became interested in this during the sixth form, and volunteered to talk to my school's maths society on the subject. These pages began as the overheads I used, but have since been substantially revised and new material added. more...
- JavaScript MD5
- I provide free JavaScript implementations of these secure hash algorithms. Their most common applications is for improving security on web login forms. more...
- Vigenere Cipher
- The is an old cipher, from the days of paper-based cryptography. With a computer it becomes quite easy to cryptanalyze. I have written a program which allows you to encrypt and decrypt strings and files. Given enough ciphertext, it can decode English plaintexts without the key. more...
- Word Patterns
- Another simple cipher is a monoalphabet. In its classic form, the key is a table mapping each plaintext letter to/from a ciphertext letter. With enough ciphertext, you can break these by making guesses such as E being the most frequent letter. You can also look for series of characters that repeat characters in the same pattern as known words, for example XJJX might be Abba, Anna, Boob, etc. This program takes a list of words, and produces a file that lets you find the words quickly, based on their pattern of repeating characters. more...
