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