Wolfenstein: The New Order certainly does have its share of secrets. The Enigma Codes, however, might be the coolest, requiring players to first find collectibles in-game, then crack a series of codes to unlock additional game modes.
While we'd love nothing more than to claim responsibility for finding and cracking the codes, we were much too busy working on our Free Wolfenstein Walkthrough. Therefore, credit for this one goes to the fine people over at PS4 Trophies, whose videos you will see embedded below. Aside from showing you how to crack the Enigma Codes, you can visit their channel to find the collectibles required to do so.
Enigma Code 1 - Unlock 999 Mode
Set 1: 01-02-03-04-05-06-07-08-09
Set 8: 08-07-06-05-04-03-02-01-09
Enigma Code 2 - Unlock Walk in the Park Mode
Set 2: 02-04-06-08-01-03-05-07-09
Set 7: 07-05-03-01-08-06-04-02-09
Enigma Code 3 - Unlock Hardcore Mode
Set 3: 03-06-09-03-06-09-03-06-09
Set 6: 06-03-09-06-03-09-06-03-09
Enigma Code 4 - Unlock Ironman Mode
Set 4: 04-08-03-07-02-06-01-05-09
Set 5: 05-01-06-02-07-03-08-04-09
Solving all four codes will unlock the Secrets Revealed I, Secrets Revealed II, Secrets Revealed III and of course, Secrets Revealed IV.