text: // Copyright (c) 2018 The Bitkincoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_CRYPTO_HKDF_SHA256_32_H
  #define BITCOIN_CRYPTO_HKDF_SHA256_32_H
  
  #include <crypto/hmac_sha256.h>
  
  #include <stdint.h>
  #include <stdlib.h>
  
  /** A rfc5869 HKDF implementation with HMAC_SHA256 and fixed key output length of 32 bytes (L=32) */
  class CHKDF_HMAC_SHA256_L32
  {
  private:
      unsigned char m_prk[32];
      static const size_t OUTPUT_SIZE = 32;
  
  public:
      CHKDF_HMAC_SHA256_L32(const unsigned char* ikm, size_t ikmlen, const std::string& salt);
      void Expand32(const std::string& info, unsigned char hash[OUTPUT_SIZE]);
  };
  
  #endif // BITCOIN_CRYPTO_HKDF_SHA256_32_H
  