/**
 * HMAC-SHA256 data-link signatures — copied from mcp-ui `src/utils/signature.ts`.
 *
 * The algorithm is load-bearing for interop: a link signed by mcp-ui must verify
 * here and vice versa. Do not "improve" the canonical string (`${id}.${exp}`),
 * the base64url digest encoding, or the epoch-seconds `exp`. Changing any of
 * them silently invalidates every link the other side issued.
 *
 * mcp-ui's exported `signDataLink` (id/exp/secret -> digest) is named
 * `computeDataLinkSignature` here so it does not collide with this package's
 * public `signDataLink(payload) -> SignedLink`. The body is unchanged.
 */
export type SignatureParams = {
    id: string;
    exp: number;
    secret: string;
};
export type SignedUrlParams = {
    id: string;
    sig: string;
    exp: number;
};
/** mcp-ui `signDataLink`: base64url HMAC-SHA256 over `${id}.${exp}`. */
export declare function computeDataLinkSignature({ id, exp, secret }: SignatureParams): string;
/** Constant-time compare, and expired links never verify. */
export declare function verifyDataLinkSignature(id: string, exp: number, sig: string, secret: string): boolean;
/** Opaque handle shape: `/v1/data-links/:id?sig=&exp=` and nothing else. */
export declare function createSignedDataUrl(baseUrl: string, id: string, exp: number, secret: string): string;
export declare function parseSignedUrlParams(url: string): SignedUrlParams | null;
export declare function generateExpiration(hoursFromNow?: number): number;
export declare function isExpired(timestamp: number): boolean;