1. Don’t Forget (Enciphered) Codes
Chris Christensen
Northern Kentucky University

2. Codes

3. World War I
Zimmermann Telegram January 1917
SMS Magdeburg
1914

4. World War II JN-25 Pearl Harbor 7 December 1941
Battle of Midway 4 – 7 June 1942

5. Encode

6. Additives

7. Additives

8. Encipher
False sum
Addition modulo 10

9. Indicator: Page/row/column 101A
9 pages
27 rows
10 columns

10. Received Message

11. Decipher 317D

12. Depth

13. Messages in Depth

14. Depth Possible attacks Brute force determination of possible
Additives.
Differencing.
Known Additives.
Known plaintext.

15. Differencing (Codegroup 1 + Additive) (Codegroup 2 + Additive)
Codegroup 1 – Codegroup 2

16. Differencing
Minor difference
2329
e minus the

17. Difference Table

18. Additive Recovery
? = 3486
3486
5554
8732

19. Text Substitution