ccs.crypt
Class AESWrapper

java.lang.Object
  ccs.crypt.AESWrapper

All Implemented Interfaces:

org.bouncycastle.crypto.BlockCipher

public class AESWrapper
extends java.lang.Object
implements org.bouncycastle.crypto.BlockCipher

A wrapper around the BouncyCastle AES engine (blend version). The wrapper provides modified key handling to cope with arbitrary-length keys; AES itself only supports 128, 192, or 256-bit keys. The rules are simple:

• Keys shorter than 8 bytes are disallowed by fiat.
• Keys whose lengths fall between the supported lengths are padded to the next allowed length.
• Keys longer than 32 bytes are presumed to be pass-phrases; these are hashed down to 160 bits, and then padded up to 192 bits.

The "blend" implementation strategy of AES was chosen over the other two - "fast" and "light" - because, in tests, the light version was slowest by a large margin, whereas the blend version was practically a dead heat with the fast version and requires usefully less space.

Field Summary

static int	BASIC Default key-transformation mode.
static int	DIGEST512 Key-transformation mode.

Constructor Summary

AESWrapper()

Method Summary

java.lang.String	getAlgorithmName()
int	getBlockSize()
void	init(boolean encrypting, org.bouncycastle.crypto.CipherParameters params)
int	processBlock(byte[] in, int inOff, byte[] out, int outOff)
void	reset()
void	setKeyTransform(int keymode) Set the key-transformation mode.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BASIC

public static final int BASIC

Default key-transformation mode. A key which is exactly 16, 24 or 32 bytes long is used as-is. A key which is less than 8 bytes long is disallowed. A key which falls between the lengths above is padded to the next defined length. A key longer than 32 bytes is hashed down to 20 bytes and padded back up to 24 bytes.

See Also:

Constant Field Values

DIGEST512

public static final int DIGEST512

Key-transformation mode. As BASIC, except that a key which is exactly 64 bytes long (512 bits) is converted into a 32-byte key by XOR-ing the two halves together.

See Also:

Constant Field Values

Constructor Detail

AESWrapper

public AESWrapper()

Method Detail

setKeyTransform

public void setKeyTransform(int keymode)

Set the key-transformation mode.

Parameters:

keymode - One of the constants defined in this class.

init

public void init(boolean encrypting,
                 org.bouncycastle.crypto.CipherParameters params)

Specified by:

init in interface org.bouncycastle.crypto.BlockCipher

getAlgorithmName

public java.lang.String getAlgorithmName()

Specified by:

getAlgorithmName in interface org.bouncycastle.crypto.BlockCipher

getBlockSize

public int getBlockSize()

Specified by:

getBlockSize in interface org.bouncycastle.crypto.BlockCipher

processBlock

public int processBlock(byte[] in,
                        int inOff,
                        byte[] out,
                        int outOff)
                 throws org.bouncycastle.crypto.DataLengthException,
                        java.lang.IllegalStateException

Specified by:

processBlock in interface org.bouncycastle.crypto.BlockCipher

Throws:

org.bouncycastle.crypto.DataLengthException

java.lang.IllegalStateException

reset

public void reset()

Specified by:

reset in interface org.bouncycastle.crypto.BlockCipher