One-Time Pad

Description

A One-Time Pad tool incorporating HMAC and keyed plaintext shuffle.

Key Features
1. Hash-Based Message Authentication Code (HMAC)
2. Fisher-Yates Shuffle
Usage Examples
Warnings
File Structures

Key Features

Hash-Based Message Authentication Code (HMAC)

HMAC is a mitigation for the inherent malleability of OTP messages. This implementation uses a quantity of bytes from the pad data as a Nonce for an HMACSHA512 MAC.

This feature makes it simple for the recipient to verify the integrity of the cyphertext and plaintext contents.

Fisher-Yates Shuffle

The Fisher-Yates keyed shuffle method is an improved approach to the Russian Copulation technique for countering known text attacks. This algorithm shuffles elements in an array based on a provided key and allows for the un-shuffling of the array given the original key.

This increases the difficulty for adversaries that are attempting a brute force decryption. Even known or expected words in the message will be shuffled into an ambiguous mixture.

Usage Examples

Create Padbook

./oneTimePad -g -b example.bin -o padDir

-g: Use a bin file to generate a directory of pad files.
-b: Path for the bin file for generating pad files.
-o: Path for the output files.

Encrypt Message

./oneTimePad -e -m message.txt -p pad1.xml -o message.xml

-e: Encrypt a plaintext message using the specified pad file.
-m: Path for the plaintext or encrypted message file.
-p: Path to the pad file.
-o: Path for the output files.

Decrypt Message

./oneTimePad -d -m message.xml -p pad1.xml -o message.txt

-d: Decrypt an encrypted message using the specified pad file.
-m: Path for the plaintext or encrypted message file.
-p: Path to the pad file.
-o: Path for the output files.

Notes

Maximum Message Length: The message must be equal to or shorter than the key.
Padding: If the message is shorter than the key this tool appends psudo-random chars to the end of the message. This is the only place a psudo-random function is used.

Warnings

Ensuring the secure deletion of files within this application poses a challenge without a universally dependable solution. Users should use operating system and storage-specific methods for securely deleting files.

For the generation of pad data, it's crucial to derive it from a true random bit source. Pseudo-random number generators are not sufficient for this purpose due to their deterministic nature.

Explore my RNG-RD project for an example of a Random Bit Generator(RBG).

File Structures

message.xml
<message>
    <mac></mac>
    <body></body>
</message>

padx.xml
<pad>
    <nonceBytes></nonceBytes>
    <shuffleBytes></shuffleBytes>
    <messageBytes></messageBytes>
</pad>

atjersland/OTP