SHOW Signed

net.rim.device.api.crypto
Class OFBPseudoRandomSource

java.lang.Object
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  +--net.rim.device.api.crypto.AbstractPseudoRandomSource
        |
        +--net.rim.device.api.crypto.OFBPseudoRandomSource

All Implemented Interfaces:

PseudoRandomSource

public final class OFBPseudoRandomSource

extends AbstractPseudoRandomSource

implements PseudoRandomSource

OFBPseudoRandomSource uses a symmetric key block cipher in Output Feedback Mode to provide a sequence of pseudo random bytes. OFB mode is defined in FIPS 81.

More than one message can be encrypted with the same key provided that a different initialization vector (IV) is used every time.

Note that any change in the ciphertext directly affects the plaintext. A ciphertext error only effects the corresponding bit of plaintext (this is why it is considered a stream cipher).

The width of the feedback is the block size of the cipher. For example, when used with DES, OFB uses 64 bit feedback.

For a code sample using the OFB pseudo random source, click here.

Category:

Signed: This element is only accessible by signed clients. If you intend to use this element, please contact RIM to establish the necessary agreements that will allow you to have your COD files signed. Signing is only required for use on the device, development under the JDE can occur without signing the CODs.

Constructor Summary

OFBPseudoRandomSource(SymmetricKeyEncryptorEngine engine, InitializationVector iv) Creates an OFBPseudoRandomSource object based on the specified encryptor engine and initialization vector.

Method Summary

	String	getAlgorithm() Returns the name of this PseudoRandomSource.
	int	getAvailable() Returns the number of pseudo random bytes currently available.
	int	getMaxAvailable() Returns the maximum number of pseudo random bytes that this PRNG can produce.
	void	xorBytes(byte[] buffer, int offset, int length) Exclusive-OR's (xor) random bytes into the given buffer starting at the specified array offset.

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.rim.device.api.crypto.PseudoRandomSource

getBytes, getBytes, getBytes, xorBytes, xorBytes, xorCopy, xorCopy

Constructor Detail

OFBPseudoRandomSource

public OFBPseudoRandomSource(SymmetricKeyEncryptorEngine engine,
                             InitializationVector iv)
                      throws CryptoTokenException

Creates an OFBPseudoRandomSource object based on the specified encryptor engine and initialization vector.

Parameters:

engine - The encryption engine (algorithm) that will be used for the OFB mode.

iv - The initialization vector that is to be used for the OFB mode (must have the same length as the engine's block length).

Throws:

CryptoTokenException - Thrown if an error occurs with the crypto token or the crypto token is invalid.

Category:

Signed: This element is only accessible by signed clients. If you intend to use this element, please contact RIM to establish the necessary agreements that will allow you to have your COD files signed. Signing is only required for use on the device, development under the JDE can occur without signing the CODs.

Method Detail

getAlgorithm

public String getAlgorithm()

Returns the name of this PseudoRandomSource. SymmetricKeyEncryptorEngine.getAlgorithm() + "/OFB".

Specified by:

getAlgorithm in interface PseudoRandomSource

Following copied from interface: net.rim.device.api.crypto.PseudoRandomSource

Returns:

A String representing the name of the algorithm.

Category:

Signed: This element is only accessible by signed clients. If you intend to use this element, please contact RIM to establish the necessary agreements that will allow you to have your COD files signed. Signing is only required for use on the device, development under the JDE can occur without signing the CODs.

xorBytes

public void xorBytes(byte[] buffer,
                     int offset,
                     int length)
              throws CryptoTokenException

Description copied from interface: PseudoRandomSource

Exclusive-OR's (xor) random bytes into the given buffer starting at the specified array offset.

Specified by:

xorBytes in interface PseudoRandomSource

Overrides:

xorBytes in class AbstractPseudoRandomSource

Since:

JDE 3.6

Category:

Signed: This element is only accessible by signed clients. If you intend to use this element, please contact RIM to establish the necessary agreements that will allow you to have your COD files signed. Signing is only required for use on the device, development under the JDE can occur without signing the CODs.

getAvailable

public int getAvailable()

Description copied from interface: PseudoRandomSource

Returns the number of pseudo random bytes currently available.

For PRNG sources that have an indefinite length but implement this interface, the value returned is Integer.MAX.

Specified by:

getAvailable in interface PseudoRandomSource

Following copied from interface: net.rim.device.api.crypto.PseudoRandomSource

Returns:

An integer that represents the number of bytes.

Throws:

CryptoTokenException - Thrown when a problem occurs with a crypto token or the crypto token is invalid.

Category:

Signed: This element is only accessible by signed clients. If you intend to use this element, please contact RIM to establish the necessary agreements that will allow you to have your COD files signed. Signing is only required for use on the device, development under the JDE can occur without signing the CODs.

getMaxAvailable

public int getMaxAvailable()

Description copied from interface: PseudoRandomSource

Returns the maximum number of pseudo random bytes that this PRNG can produce.

For PRNG sources that have an indefinite length but implement this interface, the value returned is Integer.MAX.

Specified by:

getMaxAvailable in interface PseudoRandomSource

Following copied from interface: net.rim.device.api.crypto.PseudoRandomSource

Returns:

An integer that specifies the maximum number of random bytes that can be produced.

Throws:

CryptoTokenException - Thrown when a problem occurs with a crypto token or the crypto token is invalid.

Category:

Signed: This element is only accessible by signed clients. If you intend to use this element, please contact RIM to establish the necessary agreements that will allow you to have your COD files signed. Signing is only required for use on the device, development under the JDE can occur without signing the CODs.