/**
 * @param {unknown} crit
 * @param {Record<string, unknown>} protectedHeader
 */
export function assertSignSide(crit: unknown, protectedHeader: Record<string, unknown>): void;
/**
 * @param {unknown} crit
 * @param {Record<string, unknown>} protectedHeader
 * @param {Iterable<string>} [extraKnown]
 */
export function assertVerifySide(crit: unknown, protectedHeader: Record<string, unknown>, extraKnown?: Iterable<string>): void;
/**
 * Critical header names this package understands without an explicit
 * opt-in from the verifier. JWT does not use `b64` (RFC 7797) — that
 * extension is JWS-only — so this set is empty. Add opt-in names via
 * the `knownCriticalHeaders` verify option.
 */
export const KNOWN_CRIT: Readonly<Set<never>>;