One-Time Pad (OTP) Encryption & Decryption Tool

This repository contains simple C programs to encrypt and decrypt files using the One-Time Pad (OTP) encryption technique. The encryption process uses a random key for each character, making it highly secure when used correctly.

How It Works

Encryption (enc.c)

• The encryption program reads the input file character by character.
• A random key is generated for each character using rand().
• The character is XORed with the key to produce an encrypted output.
• The key and encrypted character are saved separately in two different files.

Decryption (dec.c)

• The decryption program reads the encrypted file and the corresponding key file.
• Each encrypted character is XORed with its respective key to retrieve the original character.
• The decrypted content is saved in an output file. .

Compilation & Usage

Compile the programs:

gcc enc.c -o enc
gcc dec.c -o dec

Encrypt a file:

./enc <input_file>

• The encrypted file is saved as crypt.out.
• The corresponding key file is saved as key.out.

Decrypt a file:

./dec crypt.out key.out

• The decrypted output is saved as decrypted.out.

Important Notes

• The key file must be securely stored and never reused for different messages.
• The encryption is only as strong as the randomness of rand(), which may not be truly random.
• For true OTP security, use a cryptographically secure random number generator.
• The size of the key must be equal to the size of the message to ensure perfect secrecy.

License

This project is for educational purposes only. Use responsibly!