/*
* PBKDF
* (C) 1999-2007,2012 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#ifndef BOTAN_PBKDF_H__
#define BOTAN_PBKDF_H__

#include <botan/symkey.h>
#include <chrono>

namespace Botan {

/**
* Base class for PBKDF (password based key derivation function)
* implementations. Converts a password into a key using a salt
* and iterated hashing to make brute force attacks harder.
*/
class BOTAN_DLL PBKDF
   {
   public:

      virtual ~PBKDF() {}

      /**
      * @return new instance of this same algorithm
      */
      virtual PBKDF* clone() const = 0;

      virtual std::string name() const = 0;

      /**
      * Derive a key from a passphrase
      * @param output_len the desired length of the key to produce
      * @param passphrase the password to derive the key from
      * @param salt a randomly chosen salt
      * @param salt_len length of salt in bytes
      * @param iterations the number of iterations to use (use 10K or more)
      */
      OctetString derive_key(size_t output_len,
                             const std::string& passphrase,
                             const byte salt[], size_t salt_len,
                             size_t iterations) const;

      /**
      * Derive a key from a passphrase
      * @param output_len the desired length of the key to produce
      * @param passphrase the password to derive the key from
      * @param salt a randomly chosen salt
      * @param iterations the number of iterations to use (use 10K or more)
      */
      template<typename Alloc>
      OctetString derive_key(size_t output_len,
                             const std::string& passphrase,
                             const std::vector<byte, Alloc>& salt,
                             size_t iterations) const
         {
         return derive_key(output_len, passphrase, &salt[0], salt.size(), iterations);
         }

      /**
      * Derive a key from a passphrase
      * @param output_len the desired length of the key to produce
      * @param passphrase the password to derive the key from
      * @param salt a randomly chosen salt
      * @param salt_len length of salt in bytes
      * @param msec is how long to run the PBKDF
      * @param iterations is set to the number of iterations used
      */
      OctetString derive_key(size_t output_len,
                             const std::string& passphrase,
                             const byte salt[], size_t salt_len,
                             std::chrono::milliseconds msec,
                             size_t& iterations) const;

      /**
      * Derive a key from a passphrase using a certain amount of time
      * @param output_len the desired length of the key to produce
      * @param passphrase the password to derive the key from
      * @param salt a randomly chosen salt
      * @param msec is how long to run the PBKDF
      * @param iterations is set to the number of iterations used
      */
      template<typename Alloc>
      OctetString derive_key(size_t output_len,
                             const std::string& passphrase,
                             const std::vector<byte, Alloc>& salt,
                             std::chrono::milliseconds msec,
                             size_t& iterations) const
         {
         return derive_key(output_len, passphrase, &salt[0], salt.size(), msec, iterations);
         }

      /**
      * Derive a key from a passphrase for a number of iterations
      * specified by either iterations or if iterations == 0 then
      * running until seconds time has elapsed.
      *
      * @param output_len the desired length of the key to produce
      * @param passphrase the password to derive the key from
      * @param salt a randomly chosen salt
      * @param salt_len length of salt in bytes
      * @param iterations the number of iterations to use (use 10K or more)
      * @param msec if iterations is zero, then instead the PBKDF is
      *        run until msec milliseconds has passed.
      * @return the number of iterations performed and the derived key
      */
      virtual std::pair<size_t, OctetString>
         key_derivation(size_t output_len,
                        const std::string& passphrase,
                        const byte salt[], size_t salt_len,
                        size_t iterations,
                        std::chrono::milliseconds msec) const = 0;
   };

}

#endif