🐇 Rabbit Stream Cipher (C++ & ARM64 Assembly)

This project is a Rabbit stream cipher implementation in both C++ and ARM64 Assembly, designed for performance benchmarking and educational understanding of low-level cryptographic operations.

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🚀 Features

• Full implementation of Rabbit cipher key setup and encryption
• Parallel C++ and ARM64 Assembly versions for comparison
• Easy-to-read structure for learning or extending the cipher
• Tested with sample plaintext and 128-bit key

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🧠 What Is Rabbit Cipher?

Rabbit is a high-speed stream cipher designed for software applications. It was one of the finalists in the eSTREAM project and is known for its balance between performance and security.

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🗂️ Project Structure

.
├── main.cpp     # C++ implementation and test harness
├── asm.s        # ARM64 Assembly implementation of key setup and encryption
├── README.md    # You are here 🚀

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🔧 Build Instructions

You'll need an ARM64 environment (e.g., Apple Silicon Mac or QEMU/VM with ARM64 Linux). Then:

# Assemble and link
as -o asm.o asm.s
g++ -o rabbit main.cpp asm.o
./rabbit

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📌 Usage

The main.cpp file contains two demos:

• main1() uses the C++ implementation
• main2() uses the Assembly implementation

Both perform the following:

1. Encrypt the string "Hello, Rabbit Cipher!" using a 128-bit key.
2. Print the encrypted hex bytes.
3. Decrypt the ciphertext to recover the original plaintext.

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📷 Example Output

****************CPP****************
Original: Hello, Rabbit Cipher!
Encrypted: 3F 1A 9C ...
Decrypted: Hello, Rabbit Cipher!
****************ASM****************
Original: Hello, Rabbit Cipher!
Encrypted: 3F 1A 9C ...
Decrypted: Hello, Rabbit Cipher!

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🛠️ Functions

In C++:

• rabbit_key_setup – Initializes internal state with the key
• rabbit_crypt – Encrypts or decrypts data using keystream XOR

In Assembly:

• rabbit_key_setup_ – Optimized key setup (.global)
• rabbit_crypt_ – Optimized stream encryption

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🎯 Goals

• Verify correctness and consistency between C++ and Assembly
• Learn inner workings of Rabbit cipher and ARM64 calling conventions
• Explore cryptographic implementation at the hardware level

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📖 References

• Rabbit Cipher Specification (eSTREAM)
• ARM64 Instruction Set Manual
• Cryptography and Network Security by William Stallings (for conceptual clarity)