AESSmall256 Class Reference

AES block cipher with 256-bit keys and reduced memory usage. More...

#include <AES.h>

Inheritance diagram for AESSmall256:

Public Member Functions
	AESSmall256 ()
	Constructs an AES 256-bit block cipher with no initial key. More...
bool	setKey (const uint8_t *key, size_t len)
	Sets the key to use for future encryption and decryption operations. More...
void	decryptBlock (uint8_t *output, const uint8_t *input)
	Decrypts a single block using this cipher. More...
void	clear ()
	Clears all security-sensitive state from this block cipher. More...
Public Member Functions inherited from AESTiny256
	AESTiny256 ()
	Constructs an AES 256-bit block cipher with no initial key. More...
size_t	blockSize () const
	Size of an AES block in bytes. More...
size_t	keySize () const
	Size of a 256-bit AES key in bytes. More...
void	encryptBlock (uint8_t *output, const uint8_t *input)
	Encrypts a single block using this cipher. More...
Public Member Functions inherited from BlockCipher
	BlockCipher ()
	Constructs a block cipher.
virtual	~BlockCipher ()
	Destroys this block cipher object. More...

Detailed Description

AES block cipher with 256-bit keys and reduced memory usage.

This class differs from the AES256 class in that the RAM requirements are vastly reduced. The key schedule is expanded round by round instead of being generated and stored by setKey(). The performance of encryption and decryption is slightly less because of this.

This class is useful when RAM is at a premium and reduced encryption performance is not a hindrance to the application.

The companion AESTiny256 class uses even less RAM but only supports the encryptBlock() operation. Block cipher modes like CTR, EAX, and GCM do not need the decryptBlock() operation, so AESTiny256 may be a better option than AESSmall256 for many applications.

See also

AESTiny256, AES256

Definition at line 137 of file AES.h.

Constructor & Destructor Documentation

AESSmall256()

AESSmall256::AESSmall256

(

)

Constructs an AES 256-bit block cipher with no initial key.

This constructor must be followed by a call to setKey() before the block cipher can be used for encryption or decryption.

Definition at line 308 of file AES256.cpp.

Member Function Documentation

clear()

void AESSmall256::clear ( )

virtual

Clears all security-sensitive state from this block cipher.

Security-sensitive information includes key schedules and any temporary state that is used by encryptBlock() or decryptBlock() which is stored in the object itself.

See also

setKey(), encryptBlock(), decryptBlock()

Reimplemented from AESTiny256.

Definition at line 395 of file AES256.cpp.

decryptBlock()

void AESSmall256::decryptBlock ( uint8_t *  output, const uint8_t *  input  )

virtual

Decrypts a single block using this cipher.

Parameters

output	The output buffer to put the plaintext into. Must be at least blockSize() bytes in length.
input	The input buffer to read the ciphertext from which is allowed to overlap with output. Must be at least blockSize() bytes in length.

See also

encryptBlock(), blockSize()

Reimplemented from AESTiny256.

Definition at line 351 of file AES256.cpp.

setKey()

bool AESSmall256::setKey ( const uint8_t *  key, size_t  len  )

virtual

Sets the key to use for future encryption and decryption operations.

Parameters

key	The key to use.
len	The length of the key.

Returns

Returns false if the key length is not supported, or the key is somehow "weak" and unusable by this cipher.

Use clear() or the destructor to remove the key and any other sensitive data from the object once encryption or decryption is complete.

See also

keySize(), clear()

Reimplemented from AESTiny256.

Definition at line 317 of file AES256.cpp.

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The documentation for this class was generated from the following files:

• AES.h
• AES256.cpp