/** Protects (encrypts + authenticates) small cookie payloads. Replace to key cookies from your own KMS
 * (a hosted-seam extension point). */
export interface ICookieProtector {
    protect(plaintext: string, purpose: string): Promise<string>;
    /** Returns null (not throw) on any tamper/decrypt failure. */
    unprotect(protectedText: string, purpose: string): Promise<string | null>;
}
/** Default cookie protector: AES-256-GCM (JWE `dir`/`A256GCM`) with a per-purpose key derived from a
 * secret via SHA-256. Uses Web Crypto, so it also runs at the edge. */
export declare class JoseCookieProtector implements ICookieProtector {
    private readonly secret;
    constructor(secret: string);
    protect(plaintext: string, purpose: string): Promise<string>;
    unprotect(protectedText: string, purpose: string): Promise<string | null>;
    /**
     * Derives the per-purpose AES key with HKDF-SHA256 rather than a bare digest.
     *
     * This was `SHA-256(secret | purpose)` — one unsalted round over the raw secret. SHA-256 is fast
     * by design, so if the secret is anything short of high-entropy random (an operator-chosen
     * passphrase, a value copied from a wiki) it is directly guessable offline from one captured
     * cookie: recovering it yields the key for every purpose, which decrypts and FORGES the correlation
     * and session cookies. HKDF is the right primitive for turning key material into per-context keys,
     * and it carries the purpose as `info` instead of splicing it into the hash input.
     */
    private deriveKey;
}