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

#include <AES.h>

Inheritance diagram for AESTiny256:

Public Member Functions
	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...

bool	setKey (const uint8_t *key, size_t len)
	Sets the key to use for future encryption and decryption operations. More...

void	encryptBlock (uint8_t output, const uint8_t input)
	Encrypts a single block using this cipher. 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 BlockCipher
	BlockCipher ()
	Constructs a block cipher.

virtual	~BlockCipher ()
	Destroys this block cipher object. More...

Detailed Description

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

This class differs from the AES256 class in the following ways:

RAM requirements are vastly reduced. The key is stored directly and then expanded to the full key schedule round by round. The setKey() method is very fast because of this.
Performance of encryptBlock() is slower than for AES256 due to expanding the key on the fly rather than ahead of time.
The decryptBlock() function is not supported, which means that CBC mode cannot be used but the CTR, CFB, OFB, EAX, and GCM modes can be used.

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

The companion AESSmall256 class supports decryptBlock() at the cost of some additional memory and slower setKey() times.

See also: AESSmall256, AES256

Definition at line 117 of file AES.h.

Constructor & Destructor Documentation

◆ AESTiny256()

AESTiny256::AESTiny256 ( )

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 189 of file AES256.cpp.

Member Function Documentation

◆ blockSize()

size_t AESTiny256::blockSize ( ) const

virtual

Size of an AES block in bytes.

Returns: Always returns 16.

Implements BlockCipher.

Definition at line 202 of file AES256.cpp.

◆ clear()

void AESTiny256::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()

Implements BlockCipher.

Reimplemented in AESSmall256.

Definition at line 277 of file AES256.cpp.

◆ decryptBlock()

void AESTiny256::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()

Implements BlockCipher.

Reimplemented in AESSmall256.

Definition at line 272 of file AES256.cpp.

◆ encryptBlock()

void AESTiny256::encryptBlock	(	uint8_t *	output,
		const uint8_t *	input
	)

virtual

Encrypts a single block using this cipher.

Parameters

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

See also: decryptBlock(), blockSize()

Implements BlockCipher.

Definition at line 226 of file AES256.cpp.

◆ keySize()

size_t AESTiny256::keySize ( ) const

virtual

Size of a 256-bit AES key in bytes.

Returns: Always returns 32.

Implements BlockCipher.

Definition at line 211 of file AES256.cpp.

◆ setKey()

bool AESTiny256::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()

Implements BlockCipher.

Reimplemented in AESSmall256.

Definition at line 216 of file AES256.cpp.

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

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ AESTiny256()

Member Function Documentation

◆ blockSize()

◆ clear()

◆ decryptBlock()

◆ encryptBlock()

◆ keySize()

◆ setKey()