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https://github.com/eliainnocenti/cryptography-exercises

Exercises for Cryptography Exam @ Polito - Cryptographic primitives in C with OpenSSL and prototype attacks in Python.
https://github.com/eliainnocenti/cryptography-exercises

asymmetric-cryptography c cryptography ctf digest encryption-decryption offensive-security openssl python rand random-number-generators random-numbers symmetric-cryptography

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Exercises for Cryptography Exam @ Polito - Cryptographic primitives in C with OpenSSL and prototype attacks in Python.

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README 

          
# Cryptography Exercises



![polito](resources/logo_polito.jpg)



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`**](C/OpenSSL/01-random-numbers/README.md)                   | Generating cryptographically secure pseudo-random numbers using OpenSSL. |

| [**`Symmetric Encryption`**](C/OpenSSL/02-symmetric-encryption/README.md)       | Implementing symmetric encryption algorithms with OpenSSL.               |

| [**`Digests and MACs`**](C/OpenSSL/03-digests-MACs/README.md)                   | Exploring cryptographic digests and MACs.                                |

| [**`Big Numbers`**](C/OpenSSL/04-big-numbers/README.md)                         | Handling big numbers in cryptographic operations.                        |

| [**`Asymmetric Cryptography`**](C/OpenSSL/05-asymmetric-cryptography/README.md) | 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`**](C/CTFs/rand/README.md)                                           | Bytewise operations on random strings to capture the flag.               |

| [**`Encryption`**](C/CTFs/enc/README.md)                                      | Various encryption challenges including padding, decryption, and more.   |

| [**`Digest`**](C/CTFs/dgst/README.md)                                         | Compute keyed digests and modify digest algorithms to capture the flag.  |

| [**`HMAC`**](C/CTFs/hmac/README.md)                                           | Compute HMAC-SHA256 of two files to capture the flag.                    |

| [**`Asymmetric`**](C/CTFs/asym/README.md)                                     | 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/`**](Python/Basics/symmetric/README.md)              | Symmetric cryptography fundamentals: key generation, block/stream ciphers, padding, AEAD, hash functions, and key derivation. |

| [**`asymmetric/`**](Python/Basics/asymmetric/README.md)            | 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/`**](Python/CTFs/symmetric/README.md)               | CTF challenges focused on symmetric cryptography attacks: padding oracles, mode vulnerabilities, cookie forgery, and implementation flaws. |

| [**`asymmetric/`**](Python/CTFs/asymmetric/README.md)             | Progressive RSA challenges (Levels 1-9) and public-key cryptosystem attacks, covering factorization, parameter attacks, and advanced cryptanalysis. |

| [**`hash/`**](Python/CTFs/hash/README.md)                         | Hash function challenges including collision attacks, length extension vulnerabilities, and cryptographic hash analysis. |



## Author



- GitHub: [@eliainnocenti](https://github.com/eliainnocenti)

- Email: [elia.innocenti@studenti.polito.it](mailto:elia.innocenti@studenti.polito.it)