Cryptanalysis Guide

These brief writeups provide a solid foundational knowledge of ciphers and how to break them. If you are new to cryptography, it is recommended that you read them in order.

Quick Reference


Most common English bigrams

Most common English trigrams

Most common English quadrigrams

Index of coincidence (IOC) of English = 0.0667

IOC of Spanish: 0.0729

More IOC statistics