/**
 * @license
 * Copyright 2022 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */
import * as ellipticCurves from '../../../subtle/elliptic_curves';
import { HpkeKem } from './hpke_kem';
import { HpkeKemEncapOutput } from './hpke_kem_encap_output';
import { HpkeKemPrivateKey } from './hpke_kem_private_key';
/** Diffie-Hellman-based P-256 and P-521 HPKE KEM variant. */
export declare class NistCurvesHpkeKem implements HpkeKem {
    private readonly hkdf;
    private readonly curve;
    private constructor();
    TEST_ONLY: (recipientPublicKey: Uint8Array, senderKeyPair: HpkeKemPrivateKey) => Promise<HpkeKemEncapOutput>;
    /** Construct HPKE KEM using `curve`. */
    static fromCurve(curve: ellipticCurves.CurveType.P256 | ellipticCurves.CurveType.P521): NistCurvesHpkeKem;
    private deriveKemSharedSecret;
    /** Helper function factored out (insecure) to facilitate unit testing. */
    private encapsulateHelper;
    encapsulate(recipientPublicKey: Uint8Array): Promise<HpkeKemEncapOutput>;
    decapsulate(encapsulatedKey: Uint8Array, recipientPrivateKey: HpkeKemPrivateKey): Promise<Uint8Array>;
    getKemId(): Uint8Array;
}