CrypTool is an excellent free tool that allows you encrypt/decrypt messages, and learn how encryption algorithms works.

The encryption of a text, consists vary by the letters that appear in the original message, so that those who read the encrypted message, will not know what is hidden behind the amalgam of letters.
The encrypted messages have been used during the various wars throughout history, to encrypt the communications and prevent the other side to know the following movements of his enemy.
The writer Edgar Allan Poe was an expert in the art of deciphering encrypted messages, and in one of their stories, “The Gold Bug”, focuses the plot and story line in the decryption of an encrypted message.

CrypTool is not limited to being a simple tool that allows us to encrypt and decrypt text messages, it also provides additional information about some of the encryption algorithms supported by the program.

This software has a wizard that guides us through the available options. When we started the wizard, we have the following possibilities:

• Encryption/Decryption: In this option we will be able to encrypt or decrypt any type of text.

• Cryptanalysis: This option analyzes an encrypted text and displays relevant statistics about the algorithm of encryption used to encrypt the text.

• Hash Functions: Here we have the opportunity to select different algorithms that compute the “Hash” of a text. The algorithms that we can select are: md5, sha-1, sha-256, ripemd160, tiger, and whirlpool.

• Math Functions: In this screen we can choose the option of factoring a number in prime numbers, or perform some operations with prime numbers: generate a prime number, or to determine if a number is prime or not.

• Codes: In this section we have several possibilities. We can encode texts to hex, base-64, decimal, binary and more. We may also encode a text to morse code and vice versa. Finally we will be able to create visual codes such as bar codes, QRcodes, etc.

• Tools: Here we have at our disposal a series of tools that allow us to encrypt a text with a password, check the strength of a password, analyze a server to detect the Heartbleed vulnerability, and a random numbers generator.

When we use the options encryption/decryption, we have the possibility of choosing between different encryption algorithms, Classical or Modern. The classics include: Caesar, Vigenère, Subsitution, Enigma, Playfair, ADFGVX, XOR, Transposition and Scytale.
In terms of the modern algorithms we will be able to choose between symmetrical encryption algorithms (AES, DES, SDES, Twofish, TEA, RC2) and asymmetric (RSA).

If we do not want to use the wizard, we can create a workspacewhere we can choose the different encryption/decryption algorithms and try them directly in the work space.
When we are working in a workspace, the number of algorithms that we can prove is greater than if we use the wizard. In addition, when we use any algorithm in the workspace, we can seel more information about the history and use of this algorithm.

“Workspaces”, increases the number of possibilities that we have when we explore and learn new encryption/decryption algorithms. Without a doubt if we have interest in the world of encryption, we can spend hours in the “workspace” mode testing new algorithms and seeing how these algorithms works.

The program is only available in English and German.

Without a doubt this is an excellent program, that will improve greatly the compression of how cryptography works, for those who are curious about this topic.