question: public OutputStreamAesEncryption ( java . io . OutputStream out , byte [ ] key , int off , int len ) { super ( out ) ; byte [ ] iv = IVGenerator . getIV ( ) ; byte [ ] nkey = new byte [ len ] ; System . arraycopy ( key , off , nkey , 0 , len ) ; cipher = new AESCipher ( true , nkey , iv ) ; try { write ( iv ) ; } catch ( IOException e ) { throw new PdfException ( PdfException . PdfEncryption , e ) ; } }
target:  Creates a new instance of OutputStreamCounter