import type { Config } from './config.js';
export type KeyState = 'cold' | 'fresh' | 'stale';
export interface KeyStatus {
    state: KeyState;
    since?: number;
    lastError?: string;
    keyCount: number;
}
export declare const base64urlDecode: (segment: string) => Uint8Array<ArrayBuffer> | null;
export declare class KeySource {
    private readonly cfg;
    private snap;
    private inflight;
    private lastForced;
    private lastAttempt;
    private lastError;
    constructor(cfg: Config);
    key(kid: string): Promise<CryptoKey>;
    prefetch(): Promise<void>;
    status(): KeyStatus;
    private error;
    private tryForceRefetch;
    private refresh;
    private fetch;
}