About CrypTool 1

CrypTool 1 (CT1) is a free Windows program for cryptography and cryptanalysis. CT1 is available in 6 languages and still one of our most popular software variants.

CT1 supports both contemporary teaching methods at schools and universities as well as awareness training for employees and civil servants. The program can be downloaded here.

Originally designed as an internal business application for information security training, CrypTool 1 has since developed into an important open-source project in the field of cryptology and IT security awareness.

The current version of CrypTool 1 offers among other things:

  • Numerous classic and modern cryptographic algorithms (encryption and decryption, key generation, secure passwords, authentication, secure protocols, etc.)

  • Visualization of several algorithms (Caesar, Enigma, RSA, Diffie-Hellman, digital signatures, AES, etc.)

  • Cryptanalysis of several algorithms (Vigenère, RSA, AES, etc.)

  • Cryptanalytical measurement methods (entropy, n-grams, autocorrelation, etc.)

  • Related auxiliary methods (primality tests, factorization, base64 encoding, etc.)

  • Number theory tutorial

  • Comprehensive online help