/**
 * base64url ↔ ArrayBuffer codecs for the browser WebAuthn API: challenges and
 * credential ids arrive base64url-encoded from the server and must become
 * ArrayBuffers for `navigator.credentials`, and the credential payloads go
 * back the other way. One copy — LoginPage and PasskeyManager each carried a
 * verbatim clone.
 */
/** base64url (padded or not) → ArrayBuffer. */
export declare function base64UrlToBuffer(b64url: string): ArrayBuffer;
/** ArrayBuffer → unpadded base64url. */
export declare function bufferToBase64Url(buffer: ArrayBuffer): string;