Class PKCS1

modules/crypt/etc/pkcs1.js:41–113

import BER from "ber";

export default class PKCS1 {
	static I2OSP(I, l) {
		var c = ArrayBuffer.fromBigInt(I);
		if (l && l > c.byteLength) {
			// prepend 0
			var d = l - c.byteLength;
			var t = new Uint8Array(d);
			for (var i = 0; i < d; i++)	// just in case
				t[i] = 0x00;
			c = t.buffer.concat(c);
		}
		return c;
	};
	static sIS2SP(sI, l) {
		if (!l) {
			l = 4;
			var c = new Uint8Array(l);
			var skip = true;
			var i = 0;
			while (--l >= 0) {
				var x;
				if ((x = (sI >>> (l*8))) != 0 || !skip) {
					c[i++] = x & 0xff;
					skip = false;
				}
			}
			if (i == 0)
				c[i++] = 0;
			c = c.slice(0, i);
		}
		else {
			// l must be <= 4
			var c = new new Uint8Array(l);
			var i = 0;
			while (--l >= 0)
				c[i++] = (sI >>> (l*8)) & 0xff;
		}
		return c.buffer;
	};
	static OS2IP(OS) {
		if (OS instanceof Uint8Array) {
			let offset = OS.byteOffset;
			OS = OS.buffer.slice(offset, offset + OS.byteLength);
		}
		return BigInt.fromArrayBuffer(OS);
	};
	static randint(max) {
		var i = BigInt.fromArrayBuffer(RNG.get(BigInt.bitLength(max) >>> 3));
		while (i >= max)
			i >>>= 1;
		return i;
	};
	static parse(buf, privFlag) {
		// currently RSA only
		var key = {};
		var ber = new BER(buf);
		if (ber.getTag() != 0x30)	// SEQUENCE
			throw new Error("PKCS1: not a sequence");