Cryptography Exercises

This repository contains materials for the Cryptography course at Politecnico di Torino, focusing on both implementation and attack scenarios to bridge theory and practice.

Overview

The exercises are divided into two main parts:

• C Programming with OpenSSL:
  Learn how to implement cryptographic primitives and protocols in C. Exercises include:

  • Random Numbers: Generating cryptographically secure pseudo-random numbers.
  • Symmetric Encryption: Implementing and understanding symmetric ciphers.
  • Digests & MACs: Working with hash functions and message authentication codes.
  • Big Numbers: Handling large integer arithmetic for crypto applications.
  • Asymmetric Cryptography: Exploring public-key techniques and RSA.

• Python for Cryptography and Attacks:
  Focus on rapid prototyping, cryptanalysis, and CTF-style challenges. Python is used for both implementing cryptographic primitives and attacking them, making it ideal for practical exploit development and cryptanalysis.

Note

For further details, refer to the course slides and materials provided during the lectures.

Repository Structure

The repository is organized as follows:

Section	Description
C/OpenSSL	Exercises using C and OpenSSL covering various cryptographic topics.
C/CTFs	Capture The Flag (CTF) challenges implemented in C, focusing on practical cryptographic problems and solutions.
Python	Python-based cryptography exercises, attacks, and CTF challenges.

C/OpenSSL

Inside the C/OpenSSL folder, exercises are structured into dedicated directories:

Exercise	Description
Random Numbers	Generating cryptographically secure pseudo-random numbers using OpenSSL.
Symmetric Encryption	Implementing symmetric encryption algorithms with OpenSSL.
Digests and MACs	Exploring cryptographic digests and MACs.
Big Numbers	Handling big numbers in cryptographic operations.
Asymmetric Cryptography	Working with asymmetric cryptography and public key operations.

C/CTFs

Inside the C/CTFs folder, exercises are structured into dedicated directories:

CTF Challenge	Description
Rand	Bytewise operations on random strings to capture the flag.
Encryption	Various encryption challenges including padding, decryption, and more.
Digest	Compute keyed digests and modify digest algorithms to capture the flag.
HMAC	Compute HMAC-SHA256 of two files to capture the flag.
Asymmetric	Find missing parameters using BIGNUM primitives to capture the flag.

Python

The Python/ directory has been significantly expanded and now includes a wide range of cryptography exercises, attacks, and CTF-style challenges. The structure is as follows:

Basics

The Basics section provides comprehensive implementations of fundamental cryptographic concepts:

Exercise/Subdirectory	Description
symmetric/	Symmetric cryptography fundamentals: key generation, block/stream ciphers, padding, AEAD, hash functions, and key derivation.
asymmetric/	Asymmetric cryptography fundamentals: prime generation, RSA operations, digital signatures, and key exchange protocols.

Attacks

The Attacks section contains practical implementations of cryptographic attack techniques:

Exercise/Subdirectory	Description
symmetric/	Attacks on symmetric cryptography: ECB/CBC attacks, padding oracle attacks, keystream reuse, and cipher vulnerabilities.
asymmetric/	Attacks on asymmetric cryptography: RSA vulnerabilities, factorization attacks, side-channel analysis, and mathematical cryptanalysis.

CTFs

The CTF section contains practical challenge scenarios designed to test and improve cryptographic attack skills:

Exercise/Subdirectory	Description
symmetric/	CTF challenges focused on symmetric cryptography attacks: padding oracles, mode vulnerabilities, cookie forgery, and implementation flaws.
asymmetric/	Progressive RSA challenges (Levels 1-9) and public-key cryptosystem attacks, covering factorization, parameter attacks, and advanced cryptanalysis.
hash/	Hash function challenges including collision attacks, length extension vulnerabilities, and cryptographic hash analysis.

Author

• GitHub: @eliainnocenti
• Email: elia.innocenti@studenti.polito.it