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/*
* Symmetric Algorithm Base Class
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#ifndef BOTAN_SYMMETRIC_ALGORITHM_H__
#define BOTAN_SYMMETRIC_ALGORITHM_H__
#include <botan/types.h>
#include <botan/exceptn.h>
#include <botan/symkey.h>
namespace Botan {
/**
* This class represents a symmetric algorithm object.
*/
class BOTAN_DLL SymmetricAlgorithm
{
public:
/**
* The maximum allowed key length.
*/
const size_t MAXIMUM_KEYLENGTH;
/**
* The minimal allowed key length.
*/
const size_t MINIMUM_KEYLENGTH;
/**
* A valid keylength is a multiple of this value.
*/
const size_t KEYLENGTH_MULTIPLE;
/**
* The name of the algorithm.
* @return name of the algorithm
*/
virtual std::string name() const = 0;
/**
* Set the symmetric key of this object.
* @param key the SymmetricKey to be set.
*/
void set_key(const SymmetricKey& key)
{ set_key(key.begin(), key.length()); }
/**
* Set the symmetric key of this object.
* @param key the to be set as a byte array.
* @param length in bytes of key param
*/
void set_key(const byte key[], size_t length)
{
if(!valid_keylength(length))
throw Invalid_Key_Length(name(), length);
key_schedule(key, length);
}
/**
* Check whether a given key length is valid for this algorithm.
* @param length the key length to be checked.
* @return true if the key length is valid.
*/
bool valid_keylength(size_t length) const
{
return ((length >= MINIMUM_KEYLENGTH) &&
(length <= MAXIMUM_KEYLENGTH) &&
(length % KEYLENGTH_MULTIPLE == 0));
}
/**
* Construct a SymmetricAlgorithm.
* @param key_min the minimum allowed key length
* @param key_max the maximum allowed key length
* @param key_mod any valid key length must be a multiple of this value
*/
SymmetricAlgorithm(size_t key_min, size_t key_max, size_t key_mod) :
MAXIMUM_KEYLENGTH(key_max ? key_max : key_min),
MINIMUM_KEYLENGTH(key_min),
KEYLENGTH_MULTIPLE(key_mod)
{}
virtual ~SymmetricAlgorithm() {}
private:
/**
* Run the key schedule
* @param key the key
* @param length of key
*/
virtual void key_schedule(const byte key[], size_t length) = 0;
};
/**
* The two possible directions for cipher filters, determining whether they
* actually perform encryption or decryption.
*/
enum Cipher_Dir { ENCRYPTION, DECRYPTION };
}
#endif
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