snapshot of https://github.com/RocketChat/Rocket.Chat.git (develop, 2026-09-16; blobs > 131072B omitted)

apps/meteor/client/lib/e2ee/helper.ts

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+export async function encryptAESCTR(counter: BufferSource, key: CryptoKey, data: BufferSource) {
+	return crypto.subtle.encrypt({ name: 'AES-CTR', counter, length: 64 }, key, data);
+}
+
+export function generateAESCTRKey(): Promise<CryptoKey> {
+	return crypto.subtle.generateKey({ name: 'AES-CTR', length: 256 }, true, ['encrypt', 'decrypt']);
+}
+
+/**
+ * Generates 12 uniformly random words from the word list.
+ *
+ * @remarks
+ * Uses {@link https://en.wikipedia.org/wiki/Rejection_sampling | rejection sampling} to ensure uniform distribution.
+ *
+ * @returns A space-separated passphrase.
+ */
+export async function generatePassphrase() {
+	const { wordlist } = await import('./wordList');
+
+	// Number of words in the passphrase
+	const WORD_COUNT = 12;
+	// We use 32-bit random numbers, so the maximum value is 2^32 - 1
+	const MAX_UINT32 = 0xffffffff;
+
+	const range = wordlist.length;
+	const rejectionThreshold = Math.floor(MAX_UINT32 / range) * range;
+
+	const words: string[] = [];
+	const buf = new Uint32Array(1);
+
+	for (let i = 0; i < WORD_COUNT; i++) {
+		let v: number;
+		do {
+			crypto.getRandomValues(buf);
+			v = buf[0];
+		} while (v >= rejectionThreshold);
+		words.push(wordlist[v % range]);
+	}
+
+	return words.join(' ');
+}
+
+export async function createSha256HashFromText(data: string) {
+	const hash = await crypto.subtle.digest('SHA-256', new TextEncoder().encode(data));
+	return Array.from(new Uint8Array(hash))
+		.map((b) => b.toString(16).padStart(2, '0'))
+		.join('');
+}
+
+export async function sha256HashFromArrayBuffer(arrayBuffer: ArrayBuffer) {
+	const hashArray = Array.from(new Uint8Array(await crypto.subtle.digest('SHA-256', arrayBuffer)));
+	return hashArray.map((b) => b.toString(16).padStart(2, '0')).join('');
+}