I found all Enigma codes, [thanks to PowerPyx' collectible guide](http://www.playstationtrophies.org/forum/wolfenstein-new-order/235133-wolfenstein-new-order-collectible-guide-gold-items-enigma-codes-letters.html). All I have to do now is solve them, but how am I supposed to do it?

Each code has 2 rows of 9 numbers ranging from 1 to 9. Each row determines the value of a letter ranging from A to J. I tried brute forcing the letters, but from AA to JJ nothing happened. Brute forcing the numbers is going to take forever, since there are one Billion different combinations for them.

Finding the collectible Enigma Codes only allows me to set a value for the corresponding number, but it doesn't look like there's a hint to solving it.

Exactly how am I supposed to find out how to solve this?