Cipher Java Projects

A set of Java projects implementing various classical ciphers, including encryption, decryption, and statistical analysis for cracking.

1. Caesar Cipher

• Description: This project implements the Caesar cipher, a simple substitution cipher that shifts letters by a fixed distance. It also includes a statistical method to crack the cipher using English letter frequencies and chi-squared analysis.

• Files: casear0.java, brutus.java, MonoAlphsubstitution.java

Features

• Encrypt and decrypt text using a Caesar shift
• Automatically crack Caesar cipher using letter frequency analysis

How to Use

1.Compile the program:

javac Caesar.java Brutus.java

2. Run Caesar cipher with a shift:

java Caesar "text to encrypt or decrypt"

3. Crack Caesar cipher without the key:

   java Brutus "encrypted text"

Example:

$ java Caesar 3 "The ships hung in the sky."

Wkh vklsv kxqj lq wkh vnb.

$ java Brutus "Wkh vklsv kxqj lq wkh vnb."

The ships hung in the sky.

2. Substitution Ciphers

Description: This project implements several substitution ciphers in an object-oriented design. It includes:

1. Substitution – abstract class implementing the Cipher interface for character-by-character encryption/decryption.

2. MonoAlphaSubstitution – monoalphabetical substitution cipher with a customizable key.

3. Caesar – special case of monoalphabetical substitution with a fixed shift.

4. Vigenere – polyalphabetic substitution cipher using a keyword for encryption/decryption.

• Files: caesar.java, substitution.java, monoAlphaSubstitution.java, Vigenere.java

Features

-Encrypt/decrypt with monoalphabetical substitution

-Encrypt/decrypt with Caesar cipher

-Encrypt/decrypt with Vigenère cipher

-Validates command-line arguments for proper usage

How to Use

1.Compile the project:

javac Substitution.java MonoAlphaSubstitution.java Caesar.java Vigenere.java

2. Run MonoAlphaSubstitution:

java MonoAlphaSubstitution encrypt "text"

java MonoAlphaSubstitution decrypt "text"

3. Run Caesar:

   java Caesar encrypt "text"

   java Caesar decrypt "text"

4. Run Vigenère:

java Vigenere encrypt "text"

java Vigenere decrypt "text"

Shared files

cipher.java