In the version of Triple-DES that is used here, a threefold encryption operation is performed with two different DES keys:
The plaintext block is DES-encrypted with the first key.
The resulting block is DES-decrypted with the second key.
The resulting block is now DES-encrypted once more with the first key.
Decryption entails alternating between encryption and decryption in the reverse sequence. This method is also known as Encrypt-Decrypt-Encrypt (EDE).
As in DES, CrypTool offers both CBC mode and ECB mode.
The key is entered in the Key entry dialog.
CrypTool contains a tool which performs a Brute-force attack on the Triple-DES encryption algorithm in CBC mode.
In the Examples chapter there is one example which covers both encryption and decryption using the Triple-DES encryption algorithm in CBC mode and also the Brute-force attack.