Cryptanalysis

1. Cryptanalysis codes & ciphers

2. Simple Substitution Reciprocal system works both ways A = Z, and Z = A • Atbash cipher • A is replaced with Z, B with Y, etc.

3. Simple Substitution Non-reciprocal system the alphabet is written out twice • Keyboard cipher • QWERTY becomes ABCDEF, etc. • recipient labels the buttons on the keyboard so that when the enciphered message is typed, the plaintext is revealed

4. Simple Substitution • Caesar shift • each letter is shifted a set number of spaces • Variable shift • using a key number

5. Simple Substitution • Random alphabet table • Key word • key word first • remove repeated letters • the rest of the alphabet follows in sequence

6. More on Simple Substitution • Orphan Annie cipher • create a non-reciprocal alphabet table, where the top row is A-Z and the bottom row is random • starting with A, create a new sequence of letters (A  J  S  C, etc.) • use the new sequence to form a new alphabet table and perform a Caesar shift • recipient needs a copy of the original table

7. Pigpen • Original form • Alternate arrangements • Use key word for added complexity

8. Other Simple Substitution Ciphers Non-reciprocal substitution • Cipher disc • Saint Cyr slide Substitution with symbols • Hieroglyphics • Shadow cipher • Babington code • a nomenclator

9. Other Simple Substitution Ciphers • Algebraic equation • letters are assigned numeric values, based on their positions in the alphabet • x is the number from the ciphertext • solving for y gives the plaintext value • only positive integers count, others are nulls