Cryptography Implementation in Java

This project contains implementations of various cryptographic algorithms and utilities in Java. It demonstrates symmetric encryption (AES, DES, 3DES), asymmetric encryption (RSA), and basic cryptographic utilities.

Files Overview

Core Cryptographic Implementations

AES.java

Implementation of the Advanced Encryption Standard (AES) symmetric encryption algorithm.

• Uses AES-128 with CBC mode and PKCS5 padding
• Demonstrates key generation, encryption, and decryption
• Includes Base64 encoding for encrypted output
• Uses a 16-byte initialization vector (IV) for CBC mode

DES.java

Implementation of the Data Encryption Standard (DES) symmetric encryption algorithm.

• Uses DES with CBC mode and no padding (requires input to match block size)
• Demonstrates key generation from a string
• Shows encryption and decryption processes
• Includes Base64 encoding for encrypted output

TDES.java

Implementation of Triple DES (3DES) encryption algorithm.

• Uses DESede (Triple DES) with CBC mode and PKCS5 padding
• Demonstrates key generation from a custom 24-byte key
• Shows encryption and decryption with proper padding
• Includes Base64 encoding for encrypted output

RSA.java

Implementation of RSA asymmetric encryption algorithm.

• Generates 2048-bit RSA key pairs
• Demonstrates public key encryption and private key decryption
• Shows key pair generation and usage
• Includes Base64 encoding for encrypted messages

RSASignandEncrypt.java

Advanced RSA implementation combining digital signatures and encryption.

• Generates separate key pairs for Alice and Bob
• Demonstrates the concept of signing with private key and encrypting with public key
• Creates a signed message digest with SHA256 for verification
• Shows a hybrid approach for secure communication

RSAwithSignature.java

Complete implementation of RSA encryption with digital signatures for secure communication.

• Dual Key Pairs: Generates separate RSA key pairs for Alice (sender) and Bob (receiver)
• Message Signing: Alice signs the message using her private key with SHA256withRSA
• Message Encryption: Alice encrypts the message using Bob's public key
• Message Decryption: Bob decrypts the message using his private key
• Signature Verification: Bob verifies the signature using Alice's public key
• Complete Workflow: Demonstrates end-to-end secure communication with both confidentiality and authenticity
• Security Features:
  • Ensures message confidentiality (only Bob can decrypt)
  • Ensures message authenticity (proves message came from Alice)
  • Prevents tampering (signature verification fails if message is modified)

Utility Classes

Basic.java

Collection of basic cryptographic and mathematical utilities.

• isPrime(int x): Checks if a number is prime
• isCoPrime(BigInteger x, BigInteger y): Checks if two numbers are coprime
• totient(BigInteger x): Calculates Euler's totient function
• euclidean(): Implements the Euclidean algorithm for finding GCD

Features

• Symmetric Encryption: AES, DES, and 3DES implementations
• Asymmetric Encryption: RSA encryption and key pair generation
• Digital Signatures: RSA-based signing (in progress)
• Mathematical Utilities: Prime checking, GCD calculation, totient function
• Base64 Encoding: All encrypted outputs are Base64 encoded for safe transmission
• Multiple Cipher Modes: CBC mode with proper initialization vectors

Usage

To run any of the implementations:

javac <filename>.java
java <classname>

For example:

javac AES.java
java AES

Security Notes

• The implementations use hardcoded keys and IVs for demonstration purposes
• In production environments, use secure random key generation
• The DES algorithm is considered insecure for modern applications
• Always use proper padding and initialization vectors
• RSA key size of 2048 bits is currently considered secure

Dependencies

This project uses standard Java cryptography libraries:

• javax.crypto.* for symmetric encryption
• java.security.* for asymmetric encryption and key management
• java.util.Base64 for encoding
• java.math.BigInteger for large number operations

Educational Purpose

This project is designed for educational purposes to demonstrate:

• Different types of encryption algorithms
• Key generation and management
• Proper use of initialization vectors and padding
• Basic cryptographic mathematical operations