XOR Encryption Utility

This utility is a multi-threaded XOR encryptor/decryptor written in C++. It performs a simple XOR cryptographic transform on input data using a key provided from an external file. The utility supports multiple threads for parallel processing and ensures consistent output regardless of thread count.

Features

• XOR encryption and decryption with a rotating key.
• Multi-threaded processing for large data.
• Consistent output across single-threaded and multi-threaded runs.

Usage

Command Syntax

./encryptUtil -n <number_of_threads> -k <keyfile> < input_plaintext > output_cyphertext

Parameters

• -n <number_of_threads>: Number of threads for parallel processing.
• -k <keyfile>: Path to the file containing the XOR key.
• < input_plaintext>: Input plaintext data to be encrypted or decrypted.
• > output_cyphertext: Output file for the result.

Examples

Encrypt with a single thread:

./encryptUtil -n 1 -k keyfile < plaintext > cyphertext

Encrypt with multiple threads (e.g., 4 threads):

./encryptUtil -n 4 -k keyfile < plaintext > cyphertext

Decrypt (using the same key):

./encryptUtil -n 4 -k keyfile < cyphertext > decrypted_plaintext

Verify the decryption:

diff plaintext decrypted_plaintext

Sample Data Creation

To create sample plaintext and keyfile:

echo -n -e '����' > plaintext
echo -n -e 'ðð' > keyfile

File Inspection

To inspect the binary contents of files:

hexdump -C <filename>

Build Instructions

Requirements

• GCC with C++17 support
• POSIX-compliant system (Linux, macOS, etc.)

Compilation

To compile the utility:

make

Cleaning Up

To clean up the compiled files:

make clean

Performance Testing

Test the utility with large files and multiple threads:

dd if=/dev/urandom bs=1M count=100 of=large_plaintext
time ./encryptUtil -n 1 -k keyfile < large_plaintext > large_cyphertext_single
time ./encryptUtil -n 4 -k keyfile < large_plaintext > large_cyphertext_multi

Notes

• Ensure the keyfile is non-empty and matches the expected binary format.
• The program supports plaintext files of any size, even exceeding available memory.

License

This project is licensed under the MIT License. See the LICENSE file for details.