As NEMA is a symmetric encryption, the same steps are used for encryption and decryption.

• Setting the inner key: the incremental rollers are each combined with a contact roller.
  • Training machine:
    four advancing rollers 16, 19, 20, 21
    four contact rollers A, B, C, D
  • War machine:
    six advancing rollers 12, 13, 14, 15, 17, 18
    six contact rollers A, B, C, D, E, F
• Setting the outer key: any combination of 10 letters.
• Entering the text.

Challenge Modest character set

NEMA only knows the 26 letters. The space bar and numbers are missing.

As a workaround, arrangements were made for the display of spaces and numbers.

If these agreements are made in plain text, the corresponding switchovers take place. I.e.

• the combination XY stands for a space
• with X, the following letters are interpreted as digits:
  Q, W, E, R, … O, P => 1, 2, 3, 4, … 9, 0
• Y switches back to letters.

During decryption, these agreements are interpreted accordingly and also output.