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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_DLL Key_Length_Specification
{
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
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