miscreant/release/internals/block.js

Misuse resistant symmetric encryption library providing AES-SIV (RFC 5297), AES-PMAC-SIV, and STREAM constructions

"use strict";
/** Type which represents AES blocks */
Object.defineProperty(exports, "__esModule", { value: true });
const constant_time_1 = require("./constant-time");
const wipe_1 = require("./wipe");
/** An AES block (128-bits) */
class Block {
    constructor() {
        this.data = new Uint8Array(Block.SIZE);
    }
    /**
     * Clear the given array by setting its values to zero.
     *
     * WARNING: The fact that it sets bytes to zero can be relied on.
     *
     * There is no guarantee that this function makes data disappear from memory,
     * as runtime implementation can, for example, have copying garbage collector
     * that will make copies of sensitive data before we wipe it. Or that an
     * operating system will write our data to swap or sleep image. Another thing
     * is that an optimizing compiler can remove calls to this function or make it
     * no-op. There's nothing we can do with it, so we just do our best and hope
     * that everything will be okay and good will triumph over evil.
     */
    clear() {
        wipe_1.wipe(this.data);
    }
    /**
     * Make a copy of this block, returning a new block
     */
    clone() {
        const ret = new Block();
        ret.copy(this);
        return ret;
    }
    /** Copy the contents of another block into this one */
    copy(other) {
        this.data.set(other.data);
    }
    /**
     * Double a value over GF(2^128):
     *
     *     a<<1 if firstbit(a)=0
     *     (a<<1) ⊕ 0¹²⁰10000111 if firstbit(a)=1
     */
    dbl() {
        let carry = 0;
        for (let i = Block.SIZE - 1; i >= 0; i--) {
            const b = (this.data[i] >>> 7) & 0xff;
            this.data[i] = (this.data[i] << 1) | carry;
            carry = b;
        }
        this.data[Block.SIZE - 1] ^= constant_time_1.select(carry, Block.R, 0);
        carry = 0;
    }
}
/** Size of a block as used by the AES cipher */
Block.SIZE = 16;
/** Minimal irreducible polynomial for a 128-bit block size */
Block.R = 0x87;
exports.default = Block;