lava.security.des
Class DesCbcDecoder

java.lang.Object
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  +--lava.security.des.DesCbcCoder
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        +--lava.security.des.DesCbcDecoder

public class DesCbcDecoder

extends DesCbcCoder

DES decryption in Cipher Block Chaining (CBC) mode.

Details: DesCbcEncoder performs DES decryption in Cipher Block Chaining (CBC) mode. See superclass documention for more details.

Since:

1999.08.16

Author:

Sharky

See Also:

DesCbcEncoder

Constructor Summary

DesCbcDecoder(DesKey key, long iv)
Specifies encryption key and initialization vector.

DesCbcDecoder(IBlockCipher64 engine, long iv)
Specifies initialization vector and encryption function.

Method Summary

void	beginTransform() Resets transform.
int	continueTransform(byte[] input, byte[] output, int length) Encrypts blocks using byte arrays.
int	continueTransform(java.lang.Object input, java.lang.Object output, int length) Processes text.

Methods inherited from class lava.security.des.DesCbcCoder

completeTransform, getTransformInputWidth, getTransformOutputWidth

Methods inherited from class java.lang.Object

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

Constructor Detail

DesCbcDecoder

public DesCbcDecoder(IBlockCipher64 engine,
                     long iv)

Specifies initialization vector and encryption function.

Details: This constructor initializes a new instance with the given block cipher and initialization vector.

Parameters:

engine - the block cipher

iv - the initialization vector

DesCbcDecoder

public DesCbcDecoder(DesKey key,
                     long iv)

Specifies encryption key and initialization vector.

Details: This constructor initializes a standard DES CBC cipher with the given initialization vector and DES encryption key.

Parameters:

key - the encryption key

iv - the initialization vector

Method Detail

beginTransform

public final void beginTransform()

Description copied from interface: ITextTransform

Resets transform.

Details: beginTransform initializes this transform in preparation for processing a new input text stream.

continueTransform

public final int continueTransform(java.lang.Object input,
                                   java.lang.Object output,
                                   int length)

Description copied from interface: ITextTransform

Processes text.

Details: continueTransform consumes input text and produces output text. Input is retrieved from the provided source array (src), while output is stored in the provided destination array (dest). The return value normally indicates the number of symbols written into the destination array (see note below).

Depending on the particular transformation represented by this implementation, the number of output symbols produced per call may always be equal to the number of input symbols consumed (for example, if the transformation performs text compression). Similarly, a call to this method may cause the production of more elements than the supplied destination array can store. It is the caller's responsibility to make sure the supplied destination array is large enough to receive the symbols produced.

If the destination array is too short, the implementation may, at its option, discard the overflow. However, an implementation may also choose to retain the overflow portion and make it available in a subsequent call to this method. (Check the implementation documentation to see which approach is taken.) If the overflow is discarded, the return value must indicate the number of symbols written into the array plus the number of overflow symbols discarded.

It is legal to call this method with src set to null so long as length is also set to 0. This might be useful in situations where a transform is expected to produce output symbols even when the caller has no input symbols to supply (i.e., to recover buffered overflow from a previous call).

continueTransform always writes as much data into dest as can be computed from the current input history. However, because some data may not be computable until the transformation sees the last symbol (such as in checksum algorithms), it may be necessary to obtain the rest of the output data by calling completeTransform.

The results of continueTransform are undefined if it is called after completeTransform but before beginTransform.

Tags copied from interface: ITextTransform

Parameters:

src - the source array

dest - the destination array

length - number of symbols to process

Returns:

number of elements written into dest or discarded

continueTransform

public final int continueTransform(byte[] input,
                                   byte[] output,
                                   int length)

Encrypts blocks using byte arrays.

Details: This method is not part of the ITextTransform API, but it is provided to facilitate symbol processing where the symbols are stored in big endian byte arrays.

The length parameter and return value count bytes, not 64-bit blocks. Results are undefined if length is positive and not a multiple of 8.

Parameters:

input - the input blocks

output - buffer for output blocks

length - number of input array elements to process

Returns:

number of bytes written to output array