/**
 * @file prf.ts
 * @description TLS 1.2 pseudo-random function (RFC 5246 §5) with SHA-256.
 * @module dtls/prf
 *
 * The cipher suite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 uses P_SHA256 for
 * the PRF. This module also exposes the underlying HMAC-based P_hash.
 */
/**
 * P_hash(secret, seed) expanded to `length` bytes (RFC 5246 §5).
 *   A(0) = seed
 *   A(i) = HMAC(secret, A(i-1))
 *   P_hash = HMAC(secret, A(1)+seed) | HMAC(secret, A(2)+seed) | ...
 *
 * @param hashAlg - Node hash name, e.g. 'sha256'.
 * @param secret
 * @param seed
 * @param length
 */
export declare function pHash(hashAlg: string, secret: Buffer, seed: Buffer, length: number): Buffer;
/**
 * TLS 1.2 PRF = P_SHA256(secret, label + seed).
 *
 * @param secret
 * @param label - ASCII label, e.g. "master secret".
 * @param seed
 * @param length
 */
export declare function prf(secret: Buffer, label: string, seed: Buffer, length: number): Buffer;