/** HMAC-<alg> with a secret + message → hex string. */
export declare function webCryptoHmacHex(algorithm: "SHA-1" | "SHA-256" | "SHA-512", secret: string, message: string): Promise<string>;
/** Constant-time string equality — used everywhere signatures are
*  compared. */
export declare function timingSafeEqual(a: string, b: string): boolean;
export declare function bytesToHex(bytes: Uint8Array): string;
export declare function b64ToBytes(value: string): Uint8Array;