$ md5sum prediction.txt
16c02065ecdd742048d78181dbbeae8d prediction.txt
I saw linux installed on a computer once in my life. md5sum ??
Something simpler please
If you use Microsoft Windows. They have a free tool for it here, along with some instructions.
http://support.microsoft.com/kb/841290
Download FCIV, then run
FCIV -md5 -sha1 (path/filename)
If you post the hash (the result of running the FCIV program on the text file in which you write your prediction) then you can prove that the prediction is unchanged later when you choose to reveal what it was because people can check the hash and see that it was the same then as now.