i was thinking about this random, the problem with random based on time is the only was to get the value back to wait said time for it to be realised again! this would be a problem if the code used was generated after 30mins.
by far the easiest way is to let the user create an open Pin Number that is used to create how the data is selected, ie what button to press when selecting the code for loading and shown when save info is displayed.
what i would do is capture a sequence of random numbers based on a fixed seed to a vector from the start gate trigger, say 100 ticks worth and then modulate the Pin Number with this sequence somehow, and use these values to randomly set whether lb/rb is used to select the load alphanumeric data or used at the end of the game to display if the code is Lb or Rb selected. again i'd have this save data displayed well after the replay repeats so there is no chance for any other player to see the Lb/Rb code, they will only see the player inputting the base code at the start with no clue as to what Lb/Rb sequence is used.
i personally wouldn't care if anyone wanted to guess at a code, would be interesting to see if they can break or hack it, kudos if they do

. it all depends on what kind of CRC (type thing) you want to do to the data for testing integrity, i'd have some checks based on bare bones 'what is possible' to do in game.
could be:
Ammo count as ammo has an upper limit
location, room ID would restrict the data
if player on a platform
weapon in hand, again limited number of weapon IDs
just some of the integrity checks that can be done.
or really by far the easiest thing to do is have a save to server in place of the replay system *hint hint*