A Java program that decrypts classical ciphers without keys using frequency analysis. Includes support for simple (mono alphabetic) substitution cipher, Vigenere cipher, Caesar cipher, Vernam cipher, and variations.

Automated cryptanalysis of the Vigenère cipher using Kasiski examination, Index of Coincidence (IC), and Mutual Index of Coincidence (MIC). Recovers keys (length ≤ 5) and decrypts ciphertexts into plaintext. Implemented in Python for cryptography and cybersecurity applications.