Pseudo-Random Number Generator

Overview

This project implements a Pseudo-Random Number Generation technique for generating encryption keys. It involves key generation using both system entropy and standard libraries.

This program will iterate through a range of seeds and attempt to decrypt a known ciphertext using the generated keys. If the correct key is found, it will print the seed and the corresponding key.

Find the Pseudo-Random Number Generation Lab here

Download SEED-Ubuntu 24.04

Components

Project structure:

pseudo_rng/
├── generate_256bit_key
├── generate_256bit_key.c
├── generate_key
├── generate_key.c
├── guess_key
├── guess_key.c
└── README.md

• generate_256bit_key.c:

Generates a 256-bit key using /dev/urandom for high-quality randomness.

• generate_key.c:

Generates a 128-bit key using the standard library's rand() function seeded with the current time.

• guess_key.c:

Attempts to guess a key by iterating through possible seeds and decrypting known ciphertext using the generated keys.

• guess_key, generate_256bit_key, generate_key :

Executable files

Requirements

• A C compiler (e.g., GCC)
• OpenSSL library - for cryptographic functions
• SEED-Ubuntu 20.04 VM (or you can tweak your Ubuntu to have SEED's capabilities)

Part 1: Generating an Encryption Key

Create a file for generating a random key

nano generate_key.c

Check generate_key.c in the repo

Compile & Run code:

gcc generate_key.c -o generate_key
./generate_key

N|B:

• The function rand() will generate a constant sequence of random numbers, while srand() ensures there is a unique pattern every single time the code is executed.

rand()%256 keeps the generated number within the 0 to 255 range

Part 2: Guessing the Key

Create a another file for the guessing key function/program

nano guess_key.c

Check guess_key.c in the repo

Convert the timestamp given to seconds

date -d "2018-04-17 23:08:49" +%s

Compile code:

gcc guess_key.c -o guess_key
./guess_key

N|B:- Use the EVP API (for encryption/decryption and for the cipher) instead of AES_DECRYPT

Part 3: Getting random numbers from /dev/random and /dev/urandom

Generate the random numbers:

cat /dev/random | hexdump
cat /dev/urandom | hexdump

Monitor entropy:

watch -n 0.1 cat /proc/sys/kernel/random/entropy_avail

Place results in new file:

head -c 1M /dev/random > output.bin

Check output file's details:

ent output.bin

Part 4: Generating a 256-bit Encryption Key

Create a file for generating a random key

nano generate_256bit_key.c

Check generate_256bit_key.c in the repo

Compile code & and run the executable file generated:

gcc generate_256bit_key.c -o generate_256bit_key
./generate_256bit_key

+-------------------------------------+ FIN +-----------------------------------+