52 lines
1.3 KiB
TypeScript
52 lines
1.3 KiB
TypeScript
// Output Feedback
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import { ModeOfOperation } from "./mode.js";
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export class OFB extends ModeOfOperation {
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#iv: Uint8Array;
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#lastPrecipher: Uint8Array;
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#lastPrecipherIndex: number;
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constructor(key: Uint8Array, iv?: Uint8Array) {
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super("OFB", key, OFB);
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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.#lastPrecipher = this.iv;
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this.#lastPrecipherIndex = 16;
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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);
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for (let i = 0; i < ciphertext.length; i++) {
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if (this.#lastPrecipherIndex === 16) {
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this.#lastPrecipher = this.aes.encrypt(this.#lastPrecipher);
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this.#lastPrecipherIndex = 0;
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}
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ciphertext[i] ^= this.#lastPrecipher[this.#lastPrecipherIndex++];
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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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return this.encrypt(ciphertext);
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}
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}
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