mode-cbc.ts•1.61 kB
// Cipher Block Chaining
import { ModeOfOperation } from "./mode.js";
export class CBC extends ModeOfOperation {
#iv: Uint8Array;
#lastBlock: Uint8Array;
constructor(key: Uint8Array, iv?: Uint8Array) {
super("ECC", key, CBC);
if (iv) {
if (iv.length % 16) {
throw new TypeError("invalid iv size (must be 16 bytes)");
}
this.#iv = new Uint8Array(iv);
} else {
this.#iv = new Uint8Array(16);
}
this.#lastBlock = this.iv;
}
get iv(): Uint8Array { return new Uint8Array(this.#iv); }
encrypt(plaintext: Uint8Array): Uint8Array {
if (plaintext.length % 16) {
throw new TypeError("invalid plaintext size (must be multiple of 16 bytes)");
}
const ciphertext = new Uint8Array(plaintext.length);
for (let i = 0; i < plaintext.length; i += 16) {
for (let j = 0; j < 16; j++) {
this.#lastBlock[j] ^= plaintext[i + j];
}
this.#lastBlock = this.aes.encrypt(this.#lastBlock);
ciphertext.set(this.#lastBlock, i);
}
return ciphertext;
}
decrypt(ciphertext: Uint8Array): Uint8Array {
if (ciphertext.length % 16) {
throw new TypeError("invalid ciphertext size (must be multiple of 16 bytes)");
}
const plaintext = new Uint8Array(ciphertext.length);
for (let i = 0; i < ciphertext.length; i += 16) {
const block = this.aes.decrypt(ciphertext.subarray(i, i + 16));
for (let j = 0; j < 16; j++) {
plaintext[i + j] = block[j] ^ this.#lastBlock[j];
this.#lastBlock[j] = ciphertext[i + j];
}
}
return plaintext;
}
}