question: private int encryptBlock ( byte [ ] in , int inOff , byte [ ] out , int outOff ) throws DataLengthException , IllegalStateException { if ( ( inOff + blockSize ) > in . length ) { throw new DataLengthException ( "input buffer too short" ) ; } for ( int i = 0 ; i < blockSize ; i ++ ) { cbcV [ i ] ^= in [ inOff + i ] ; } int length = cipher . processBlock ( cbcV , 0 , out , outOff ) ; System . arraycopy ( out , outOff , cbcV , 0 , cbcV . length ) ; return length ; }
target:  Do the appropriate chaining step for CBC mode encryption.