Crypt includes traditional ciphers such as the Caesar Cipher, Autokey Cipher, and Railfence Cipher, as well as modern ciphers like AES, DES, and the asymmetrical cipher RSA.

How to:

Clone this repo.

Install pycryptodome if not installed already.

Note: $ is to denote terminal commands. Do not include it as part of the command.

$ pip install pycryptodome

• Python 3.x

$ pip3 install pycryptodome

Run the application.

$ python main.py

• Python 3.x

$ python3 main.py

Follow the instructions given in the command-line application.

Note: RSA will output keys and encrypted data to the subdirectory /rsa

Symmetric Encryption

Traditional Ciphers

Caesar Cipher

The Caesar Cipher is a substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet.

Encryption:

Each letter in the plaintext is shifted by a fixed number, known as the key. For example, with a key of 3, 'A' would be encrypted to 'D', 'B' to 'E', and so on.

Decryption:

Each letter in the ciphertext is shifted back by the same fixed number.

Example:

• Plaintext: HELLO
• Key: 3
• Ciphertext: KHOOR

Autokey Cipher

The Autokey Cipher is a polyalphabetic substitution cipher that uses a keyword followed by the plaintext itself to create the key.

Encryption:

A keyword is chosen and appended to the plaintext (after removing the keyword length) to create a running key. Each letter of the plaintext is shifted by the corresponding letter of the running key, where 'A' represents a shift of 0, 'B' a shift of 1, and so on.

Decryption:

The keyword is used to decipher the first part of the message. The plaintext itself is then used to decipher the remaining part.

Example:

• Plaintext: HELLO
• Keyword: KEY
• Ciphertext: RIJSS

Railfence Cipher

The Railfence Cipher is a transposition cipher that arranges the plaintext in a zigzag pattern across multiple "rails" and then reads it off row by row.

Encryption:

The plaintext is written in a zigzag pattern across a fixed number of rails. The ciphertext is obtained by reading the pattern row by row.

Decryption:

The ciphertext is written in the zigzag pattern and read off in the original order.

Example:

• Plaintext: HELLO WORLD
• Number of Rails: 3
• Ciphertext: HOREL OLLWD

Modern Ciphers

AES (Advanced Encryption Standard)

AES is a symmetric key encryption standard adopted by the U.S. government. It supports key sizes of 128, 192, and 256 bits and operates on 128-bit blocks.

Encryption:

The plaintext is divided into 128-bit blocks. Each block undergoes multiple rounds of substitution, permutation, mixing, and key addition.

Decryption:

The process is reversed using the same key to retrieve the original plaintext.

Key Features:

• Strong security
• Widely used in various applications

DES (Data Encryption Standard)

DES is a symmetric key encryption algorithm that uses a 56-bit key and operates on 64-bit blocks.

Encryption:

The plaintext is divided into 64-bit blocks. Each block undergoes 16 rounds of permutation and substitution based on the key.

Decryption:

The process is reversed using the same key to retrieve the original plaintext.

Key Features:

• Less secure by modern standards due to short key length
• Superseded by AES

Asymmetric Encryption

RSA (Rivest–Shamir–Adleman)

RSA is an asymmetric key encryption algorithm that uses a pair of keys: a public key for encryption and a private key for decryption.

Encryption:

The plaintext is encrypted using the recipient's public key. Only the recipient can decrypt the ciphertext using their private key.

Decryption:

The ciphertext is decrypted using the recipient's private key.

Key Features:

• Based on the mathematical difficulty of factoring large prime numbers
• Widely used for secure data transmission