🔐 Crypto Codes

Hey there! 👋 Welcome to my collection of cryptography algorithms implemented from your college assignments.

This repo contains various encryption, hashing, and key exchange implementations for learning and educational purposes.

🔒 Symmetric Encryption

Algorithm	Description	Time Complexity
Caesar	The classic substitution cipher that shifts characters by a fixed offset	O(n)
Playfair	Digraph substitution cipher that encrypts pairs of letters	O(n)

💡 Example usage (click to expand)

// Caesar cipher example
String plaintext = "HELLO";
int shift = 3;
String encrypted = caesar.encrypt(plaintext, shift);  // Returns "KHOOR"

🔑 Asymmetric Encryption

Algorithm	Description	Security
RSA	Public-key cryptosystem for secure data transmission	Based on factoring large integers
Diffie-Hellman	Method for securely exchanging cryptographic keys over public channels	Based on discrete logarithm problem

⚙️ Implementation details (click to expand)

// RSA simplified example
KeyPair keys = RSA.generateKeyPair(1024);
String encrypted = RSA.encrypt("Secret message", keys.publicKey);
String decrypted = RSA.decrypt(encrypted, keys.privateKey);

🧮 Hashing Algorithms

Algorithm	Description	Output Size
MD5	Widely used hash function producing a 128-bit hash value	128 bits (16 bytes)

🧠 Math Utilities

Utility	Description	Used In
Euclidean	Algorithms for computing GCD and modular inverse	RSA, many crypto systems
Buffer_Overflow	Demonstration of memory vulnerability	Security testing

📖 How to Run

☕ Java Implementations

# Compile the Java file
javac RSA.java

# Run the program
java RSA

# Example output:
# Generated keys: (public_key, private_key)
# Encrypted: a7f12d8e...
# Decrypted: Hello, world!

🔧 C Implementations

# Compile with gcc
gcc Buffer_Overflow.c -o buffer

# Run the executable
./buffer

# Example output:
# Demonstrating buffer overflow vulnerability...

🤝 Contributing

Found a bug? Have a better implementation? Want to add a new algorithm? I'd love your help!

# Fork this repository
# Create your feature branch
git checkout -b cool-new-feature

# Commit your changes
git commit -m 'Added an awesome crypto algorithm'

# Push to the branch
git push origin cool-new-feature

# Open a Pull Request 🎉

⭐ Support

If this repo helped you understand crypto concepts better, consider giving it a star! Each star motivates me to add more algorithms and improve the existing ones! ✨

Jia2005/CSS-Codes