# Cryptanalysis

## Contents

## Cryptanalysis basics

- Cryptanalysis and attacks - Wikipedia
- Amount of information available to the attacker (further to Kerckhoffs' principle)
- Ciphertext-only: the cryptanalyst has access only to a collection of ciphertexts or codetexts.
- Known-plaintext: the attacker has a set of ciphertexts to which they know the corresponding plaintext.
- Chosen-plaintext (chosen-ciphertext): the attacker can obtain the ciphertexts (plaintexts) corresponding to an arbitrary set of plaintexts (ciphertexts) of their own choosing.
- Adaptive chosen-plaintext: like a chosen-plaintext attack, except the attacker can choose subsequent plaintexts based on information learned from previous encryptions, similarly to the Adaptive chosen ciphertext attack.
- Related-key attack: Like a chosen-plaintext attack, except the attacker can obtain ciphertexts encrypted under two different keys. The keys are unknown, but the relationship between them is known; for example, two keys that differ in the one bit.

- Computational resources required
- Time – the number of computation steps (e.g., test encryptions) which must be performed.
- Memory – the amount of storage required to perform the attack.
- Data – the quantity and type of plaintexts and ciphertexts required for a particular approach.

## Illustrations