/** Parameters shared by every interoperable Argon2id implementation. */
export interface Argon2idOptions {
    password: Uint8Array;
    salt: Uint8Array;
    iterations: number;
    parallelism: number;
    memorySize: number;
    hashLength: number;
}
/**
 * Optional asynchronous Argon2id implementation supplied by a host runtime.
 *
 * A selected backend is authoritative: derivation failures are propagated and
 * never retried with another implementation. Hosts should report readiness only
 * after proving that their native implementation is available and interoperable.
 * Make preload and isReady reentrant, including calls made by the host itself.
 * Concurrent cold calls share one preload attempt. Later calls may retry after
 * settlement; hosts should cache permanent failures or apply retry backoff.
 */
export interface AsyncArgon2idBackend {
    preload: () => Promise<void>;
    isReady: () => boolean;
    deriveKey: (options: Readonly<Argon2idOptions>) => Promise<Uint8Array>;
}
/** Installs a process/page-wide optional Argon2id backend. */
export declare function registerArgon2idBackend(backend: AsyncArgon2idBackend): void;
/** Removes `backend` if it is still the active optional implementation. */
export declare function unregisterArgon2idBackend(backend: AsyncArgon2idBackend): void;
/**
 * Returns a proven-ready backend. A cold backend is prepared in the background
 * while the current derivation retains the portable implementation path.
 */
export declare function readyArgon2idBackend(): AsyncArgon2idBackend | undefined;
/** Rejects malformed alternative-backend output before it can become wallet key material. */
export declare function validateArgon2idResult(value: Uint8Array, expectedLength: number): Uint8Array;
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