supermemory/apps/web/server/encrypt.ts

function convertStringToFixedNumber(input: string): number {
	let hash = 0;
	for (let i = 0; i < input.length; i++) {
		const char = input.charCodeAt(i);
		hash = (hash * 31 + char) % 1000000007; // Hashing by a large prime number
	}
	return hash;
}

const chars = `abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-1234567890`;
const shuffled = shuffle(
	chars.split(""),
	convertStringToFixedNumber(process.env.BACKEND_SECURITY_KEY),
);

function random(seed: number) {
	const x = Math.sin(seed++) * 10000;
	return x - Math.floor(x);
}

function shuffle(array: string[], seed: number) {
	let m = array.length,
		t,
		i;

	while (m) {
		i = Math.floor(random(seed) * m--);

		t = array[m];
		array[m] = array[i]!;
		array[i] = t!;
		++seed;
	}

	return array;
}

export const cipher = (text: string) => {
	let returned_text = "";

	for (let i = 0; i < text.length; i++) {
		returned_text += shuffled[chars.indexOf(text[i]!)];
	}

	return extend(returned_text);
};

export const decipher = (text: string) => {
	let returned_text = "";
	const index = Math.floor(
		random(convertStringToFixedNumber(process.env.BACKEND_SECURITY_KEY)) *
			(text.length / 2),
	);

	for (let i = 0; i < text.length; i++) {
		returned_text += chars[shuffled.indexOf(text[i]!)];
	}
	const total = parseInt(text[index]!);
	const str = parseInt(text.slice(index + 1, index + total + 1));
	return returned_text.slice(text.length - str);
};

const extend = (text: string, length = 60) => {
	const extra = length - text.length;

	if (extra < 0) {
		return text;
	}

	// Random index to store the length of the string
	const index = Math.floor(
		random(convertStringToFixedNumber(process.env.BACKEND_SECURITY_KEY)) *
			(length / 2),
	);

	const storage_string =
		text.length.toString().length.toString() + text.length.toString();
	let returned = "";
	let total = storage_string.length + text.length;

	for (let i = 0; i < extra; i++) {
		if (i == index) {
			returned += storage_string;
		} else {
			if (total >= length) {
				break;
			}
			// Add a random character
			returned += shuffled[Math.floor(random(Math.random()) * shuffled.length)];
			total++;
		}
	}
	returned += text;
	return returned;
};