Computer Forensic Investigation and Cryptography

Caeser and Subsitution Ciphers

A Caeser cipher is simply moving all letters by a certain number down the alphabet

Most known use: ROT-13, involves moving every letter 13 across

Used in the Windows registry: letter A becomes J

Substitution Ciphers

An extension of Caeser ciphers

Essentially, 2 caeser ciphers

Encipher with X shift, then encipher again with Y shift

How to solve?

Letter frequencies

We take HELLO as ABCCD

Longer words are better to use!

Multiple alphabets

Encipher plaintext with first alphabet

Then again with second alphabet

Solved with this table: