public AesDecryptor(byte[] key,int off,int len){
  this.key=new byte[len];
  System.arraycopy(key,off,this.key,0,len);
}

public AesDecryptor ( byte [ ] key , int off , int len ) { this . key = new byte [ len ] ; System . arraycopy ( key , off , this . key , 0 , len ) ; }
creates a new instance of aesdecryption
