/**
 * @license
 * Copyright 2020 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */
/**
 * Computes an HKDF.
 *
 * @param size The length of the generated pseudorandom string in
 *     bytes. The maximal size is 255 * DigestSize, where DigestSize is the size
 *     of the underlying HMAC.
 * @param hash the name of the hash function. Accepted names are SHA-1,
 *     SHA-256 and SHA-512
 * @param ikm Input keying material.
 * @param info Context and application specific
 *     information (can be a zero-length array).
 * @param opt_salt Salt value (a non-secret random
 *     value). If not provided, it is set to a string of hash length zeros.
 * @return Output keying material (okm).
 */
export declare function compute(size: number, hash: string, ikm: Uint8Array, info: Uint8Array, opt_salt?: Uint8Array): Promise<Uint8Array>;