/**
 * Shared utilities for nostr-biometric-login-service
 */
/**
 * Convert npub to hex public key
 * @param npub The npub to convert
 */
export declare function npubToHex(npub: string): string;
/**
 * Convert hex public key to npub
 * @param hex The hex public key to convert
 */
export declare function hexToNpub(hex: string): string;
/**
 * Generate a random string of specified length
 * @param length Length of the random string
 */
export declare function generateRandomString(length: number): string;
/**
 * Check if running in browser environment
 */
export declare function isBrowser(): boolean;
/**
 * Set a cookie in the browser
 *
 * NOTE: HttpOnly cannot be set via document.cookie — it can only be set via
 * a server-side Set-Cookie header. Session cookies should be set server-side
 * with the HttpOnly flag to prevent client-side script access.
 *
 * @param name Cookie name
 * @param value Cookie value
 * @param days Days until expiry
 */
export declare function setCookie(name: string, value: string, days: number): void;
/**
 * Get a cookie value
 * @param name Cookie name
 */
export declare function getCookie(name: string): string | null;