# Decode this message:

Gongs.

Achtung! 16324 Trennung 28, 16324 Trennung 28

95220 27182 42355 04528 41268 85136 75910 93275 41209 45460 25239 06265 19939 17512 39694 83952 03747 33998 37518 73308 24473 53061 85975 08947 90886 53256 10058 82063

Ende!

Key No. 16324:

25815 62579 69763 96269 26985 22966 92962 66292 92572 47147 42785 23629 22957 25707 25072 52579 51791 25707 54701 57025 70414 70491 24805 25250 72570 27500 17575 00275

You will need to know the STASI TAPIR Code Table to convert the plaintext numbers back to letters.

You can find the table here: https://rgpsecurity.wordpress.com/2014/10/17/stasi-vernam-cipher-gernator-tapir/

• Do you have good reason to believe that this is actually solvable? (I ask because if, e.g., it's a transcription of something from an actual Cold War numbers station -- which seems to be what it's meant to look like -- then it's probably not.) – Gareth McCaughan Feb 5 at 16:29
• I wrote this message myself. The key to decode the message is provided below. Obviously a real message would be impossible for even the NSA to decode. – WAR10CK Feb 5 at 16:30
• Just checking :-). (Still going to be tough; we basically have to guess what the cipher is and how the numbers 16324 and 28 key it, and on the face of it there are an enormous number of possibilities. Maybe knowledge of the ciphers actually used by the Stasi would help, though naively I'd guess that they probably used good ones...) – Gareth McCaughan Feb 5 at 16:36
• The 5 digit number specifies the Key No. The two digit number just indicates how many 5 digit numbers make up the message as per the format for this station. The Key No. is not needed. It just indicates the page in the OTP that the correct key is found. – WAR10CK Feb 5 at 16:38
• Oh, I see, I'd been misunderstanding the question. I'll tweak the formatting since it doesn't seem as if it was intended to be confusing in the specific way it confused me. – Gareth McCaughan Feb 5 at 18:28

If we

subtract the key (which WAR10CK indicates in comments is a one-time pad) digit-by-digit from the ciphertext, remove the gaps between blocks of 5 digits, and look up in the obvious fashion in the TAPIR table,

then we get

treffen 83 sie 83 sich 83 mit 83 agent 83 hunt 83 in 83 der 83 ost 82 92 81 berliner 83 cafe 82 91 83 81 um 83 das 83 paket 83 zu 83 empfangen 82 89 8

where

I have left digits corresponding to "special" code points as they are. 92 is -, 91 is ,, 89 is ., and according to this manual,
81 = Bu, short for "Übergang zu Buchstaben" meaning "transition to letters"
82 = Zi, short for "Übergang zu Ziffern und Zeichen" meaning "transition to numbers and symbols"
83 = ZwR, short for "Zwischenraum" meaning "space"

So

the message says: "Treffen sie sich mit Agent Hunt in der Ost-Berliner Cafe, um das Paket zu empfangen." or "Meet with Agent Hunt in the East-Berlin Cafe, to receive the package".

Credit where due: thanks to an anonymous editor who improved the paragraph after "where" and provided a relevant link.

• Congrats! You figured it out! – WAR10CK Feb 6 at 16:42