code: @Override
      protected long decryptBlock(long lCipherblock) {
  
  	// save the current block
  
  	long lTemp = lCipherblock;
  
  	// decrypt the block
  
  	lCipherblock = super.decryptBlock(lCipherblock);
  
  	// dechain the block
  
  	lCipherblock ^= m_lCBCIV;
  
  	// set the new CBC IV
  
  	m_lCBCIV = lTemp;
  
  	// return the decrypted block
  
  	return lCipherblock;
  
      }
docs: internal routine to decrypt a block in CBC mode