Function getTokenKey

cwa/src/privateToken.ts:52–65

(
	privateMediaSecret: PrivateMediaSecret,
)

let maybeTokenKey: CryptoKey | null = null
async function getTokenKey(
	privateMediaSecret: PrivateMediaSecret,
): Promise<CryptoKey> {
	if (maybeTokenKey == null) {
		maybeTokenKey = await crypto.subtle.importKey(
			'raw',
			base64ToArray(privateMediaSecret),
			{ name: 'HMAC', hash: 'SHA-256' },
			false,
			['sign', 'verify'],
		)
	}
	return maybeTokenKey
}

function buildMessage(userId: UserId, mediaHash: MediaHash): ArrayBuffer {
	const encodedUserId = new TextEncoder().encode(userId)