public final byte[] computeHash(byte[] data){
  byte[] ret=null;
  hashLock.lock();
  ret=md.digest(data);
  hashLock.unlock();
  return ret;
}

public final byte [ ] computeHash ( byte [ ] data ) { byte [ ] ret = null ; hashLock . lock ( ) ; ret = md . digest ( data ) ; hashLock . unlock ( ) ; return ret ; }
computes an hash for a tom message
