How do I solve Enigma codes?

I believe the answer can be found in game. In chapter 4 when you break into the prison, you go into a room with a blackboard. on the blackboard is the following sum.

8x9=72 (7+2)= 9

If you apply this rule to the number of the enigma row and position number you should get the single digit that is the answer.

Hope this helps

It may be sweet irony, but 5 minutes before I posted my question, someone already posted the solution to the codes.

To solve Code n, you will need to do the following:

First row: Put n in the first column. To get the value of the next column, add n to the current column's value. If the value exceeds 9, use the digital root.

Second row: To get the current column's value, subtract the value of the first row's same column from 9.

0 is never part of the code. Each column adds up to either 9 or 18.

Here are the solutions and what they unlock:

Code 1

1 2 3 4 5 6 7 8 9
8 7 6 5 4 3 2 1 9

Unlocks 999

Play Wolfenstein in 999 mode.
- 999% more action
- start with 999 health
- unlimited ammo
- ÜBER difficulty

Code 2

2 4 6 8 1 3 5 7 9
7 5 3 1 8 6 4 2 9

Unlocks WALK IN THE PARK

Play Wolfenstein in WALK IN THE PARK mode.
- all HUD elements except interactive prompts disabled
- rely fully on your senses to survive
- I AM DEATH INCARNATE! difficulty

Code 3

3 6 9 3 6 9 3 6 9
6 3 9 6 3 9 6 3 9

Unlocks HARDCORE

Play Wolfenstein in HARDCORE mode.
- all health and armor pickups removed from the game
- ÜBER difficulty

Code 4

4 8 3 7 2 6 1 5 9
5 1 6 2 7 3 8 4 9

Unlocks IRONMAN

Play Wolfenstein in IRONMAN mode.
- only one life
- game over if you die
- ÜBER difficulty