key_spec.h

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/*
* Symmetric Key Length Specification
* (C) 2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#ifndef BOTAN_KEY_LEN_SPECIFICATION_H_
#define BOTAN_KEY_LEN_SPECIFICATION_H_

#include <botan/types.h>

namespace Botan {

/**
* Represents the length requirements on an algorithm key
*/
class BOTAN_PUBLIC_API(2,0) Key_Length_Specification final
   {
   public:
      /**
      * Constructor for fixed length keys
      * @param keylen the supported key length
      */
      explicit Key_Length_Specification(size_t keylen) :
         m_min_keylen(keylen),
         m_max_keylen(keylen),
         m_keylen_mod(1)
         {
         }

      /**
      * Constructor for variable length keys
      * @param min_k the smallest supported key length
      * @param max_k the largest supported key length
      * @param k_mod the number of bytes the key must be a multiple of
      */
      Key_Length_Specification(size_t min_k,
                               size_t max_k,
                               size_t k_mod = 1) :
         m_min_keylen(min_k),
         m_max_keylen(max_k ? max_k : min_k),
         m_keylen_mod(k_mod)
         {
         }

      /**
      * @param length is a key length in bytes
      * @return true iff this length is a valid length for this algo
      */
      bool valid_keylength(size_t length) const
         {
         return ((length >= m_min_keylen) &&
                 (length <= m_max_keylen) &&
                 (length % m_keylen_mod == 0));
         }

      /**
      * @return minimum key length in bytes
      */
      size_t minimum_keylength() const
         {
         return m_min_keylen;
         }

      /**
      * @return maximum key length in bytes
      */
      size_t maximum_keylength() const
         {
         return m_max_keylen;
         }

      /**
      * @return key length multiple in bytes
      */
      size_t keylength_multiple() const
         {
         return m_keylen_mod;
         }

      /*
      * Multiplies all length requirements with the given factor
      * @param n the multiplication factor
      * @return a key length specification multiplied by the factor
      */
      Key_Length_Specification multiple(size_t n) const
         {
         return Key_Length_Specification(n * m_min_keylen,
                                         n * m_max_keylen,
                                         n * m_keylen_mod);
         }

   private:
      size_t m_min_keylen, m_max_keylen, m_keylen_mod;
   };

}

#endif