# Encryption and Decryption Using Cryptool

Cryptool is an open-source and freeware program that can be used in various aspects of cryptographic and cryptanalytic concepts. There are no other programs like it available over the internet where you can analyze the encryption and decryption of various algorithms. This tools provides graphical interface, better documentation to achieve the encryption and decryption, bundles of analytic tools, and several algorithms.

## What is Cryptool?

• A freeware program with graphical user interface (GUI).
• A tool for applying and analyzing cryptographic algorithms.
• Contains nearly all state-of-the-art crypto algorithms.
• “Playful” introduction to modern and classical cryptography.
• Not a “hacker" tool.

## Encryption and Decryption of Caesar Cipher

Here, we will implement an encryption and decryption of Caesar Cipher, which is actually a substitution method of cryptography. The Caesar Cipher involves replacing each letter of the alphabet with a letter –  placed down or up according to the key given.

To start with the process you have to move to the Encrypt/Decrypt tab of the program. There, you will find Symmetric (Classic) tab - Choose Caesar Cipher. For further information, you can get guided by the image below.

Figure1: Encrypt/Decrypt of Cryptool

In encryption, we are replacing the plaintext letter with the 3rd letter of the alphabet that is if “A” is our plaintext character, then the Ciphertext will be “D”.

Figure2: Caesar Cipher

So, if I give “Monarchy” as plaintext in Caesar Cipher, it will show me the encryption, as shown in the below image.

Figure3: Caesar Cipher Encryption

## Encryption and Decryption of Playfair

Again, we have to move to Encrypt/Decrypt - Symmetric - Playfair Cipher and perform the encryption part. We are putting the same plaintext – MONARCHY.

Figure4: Playfair Cipher

So, when we press the encrypt button, we will get the Ciphertext  – “ONARMDYB”.

Figure5: Playfair Encryption

## Encryption and Decryption of Hill Cipher

Again, we have to move to Encrypt/Decrypt - Symmetric - Hill Cipher and perform the encryption part. We are putting the plaintext as – DRGREERROCKS and assuming that the program gives us the Ciphertext as – FZIFTOTBXGPO.

Figure6: Hill Cipher

So, when we press the encrypt button, we will get the Ciphertext – “FZIFTOTBXGPO”.

Figure7: Hill Cipher Encryption

## Encryption and Decryption of Vigener Cipher

Again, we have to move to Encrypt/Decrypt - Symmetric - Vigener Cipher and perform the encryption part. We are putting the plaintext as – MICHIGANTECHNOLOGICALUNIVERSITY and assuming that the program gives us the Ciphertext as – TWWNPZOAAS…..,with the help of key as – HOUGHTON.

Figure8: Vigener Cipher

So, when we press the encrypt button, we will get the Ciphertext somewhat like – “TWWNPZOAASWNUHZBNWWGSNBVCSLYPMM”.

Figure9: Vigener Cipher Encryption

## Encryption and Decryption of Railfence Cipher

Again, we have to move to Encrypt/Decrypt - Symmetric - Railfence Cipher and perform the encryption part. We are putting the plaintext as – UNBREAKABLE and assuming that the program gives us the Ciphertext as – UEBNRAALBKE…..,with the help of key as – 3.

Figure10: Railfence Cipher

So, when we press the encrypt button, we will get the Ciphertext like – “UEBNRAALBKE”.

Figure11: Railfence Cipher Encryption