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gnu.javax.crypto.sasl.srp
Class CALG  view CALG download CALG.java

java.lang.Object
  extended bygnu.javax.crypto.sasl.srp.CALG

public final class CALG
extends java.lang.Object

A Factory class that returns CALG (Confidentiality Algorithm) instances that operate as described in the draft-burdis-cat-sasl-srp-08.

The designated CALG block cipher should be used in OFB (Output Feedback Block) mode in the ISO variant, as described in The Handbook of Applied Cryptography, algorithm 7.20.

Let k be the block size of the chosen symmetric key block cipher algorithm; e.g. for AES this is 128 bits or 16 octets. The OFB mode used shall be of length/size k.

It is recommended that block ciphers operating in OFB mode be used with an Initial Vector (the mode's IV). In such a mode of operation - OFB with key re-use - the IV need not be secret. For the mechanism in question the IVs shall be a random octet sequence of k bytes.

The input data to the confidentiality protection algorithm shall be a multiple of the symmetric cipher block size k. When the input length is not a multiple of k octets, the data shall be padded according to the following scheme:

Assuming the length of the input is l octets, (k - (l mod k)) octets, all having the value (k - (l mod k)), shall be appended to the original data. In other words, the input is padded at the trailing end with one of the following sequences:


                    01 -- if l mod k = k-1
                   02 02 -- if l mod k = k-2
                             ...
                             ...
                             ...
                 k k ... k k -- if l mod k = 0

The padding can be removed unambiguously since all input is padded and no padding sequence is a suffix of another. This padding method is well-defined if and only if k < 256 octets, which is the case with symmetric key block ciphers today, and in the forseeable future.


Field Summary
private  gnu.javax.crypto.assembly.Assembly assembly
           
private  int blockSize
           
private  int keySize
           
private  java.lang.Object modeNdx
           
 
Constructor Summary
private CALG(int blockSize, int keySize, java.lang.Object modeNdx, gnu.javax.crypto.assembly.Assembly assembly)
          Private constructor to enforce instantiation through Factory method.
 
Method Summary
 byte[] doFinal(byte[] data)
          Encrypts or decrypts, depending on the mode already set, a designated array of bytes and returns the result.
 byte[] doFinal(byte[] data, int offset, int length)
          Encrypts or decrypts, depending on the mode already set, a designated array of bytes and returns the result.
(package private) static CALG getInstance(java.lang.String algorithm)
          Returns an instance of a SASL-SRP CALG implementation.
 void init(KDF kdf, byte[] iv, gnu.javax.crypto.assembly.Direction dir)
          Initialises a SASL-SRP CALG implementation.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

assembly

private gnu.javax.crypto.assembly.Assembly assembly

modeNdx

private java.lang.Object modeNdx

blockSize

private int blockSize

keySize

private int keySize
Constructor Detail

CALG

private CALG(int blockSize,
             int keySize,
             java.lang.Object modeNdx,
             gnu.javax.crypto.assembly.Assembly assembly)
Private constructor to enforce instantiation through Factory method.

Method Detail

getInstance

static CALG getInstance(java.lang.String algorithm)

Returns an instance of a SASL-SRP CALG implementation.


init

public void init(KDF kdf,
                 byte[] iv,
                 gnu.javax.crypto.assembly.Direction dir)
          throws javax.security.sasl.SaslException

Initialises a SASL-SRP CALG implementation.


doFinal

public byte[] doFinal(byte[] data)
               throws gnu.javax.crypto.sasl.ConfidentialityException

Encrypts or decrypts, depending on the mode already set, a designated array of bytes and returns the result.


doFinal

public byte[] doFinal(byte[] data,
                      int offset,
                      int length)
               throws gnu.javax.crypto.sasl.ConfidentialityException

Encrypts or decrypts, depending on the mode already set, a designated array of bytes and returns the result.