Post by bjbackitiskm4rb on Oct 25, 2019 12:02:17 GMT
This is probably a stupid question relating to the advanced M4 procedures, but I'll ask it anyway...
The same procedures for encrypting and decrypting hold true for most of the nets listed in the K-Book (Hydra, Triton, etc), and the same K-Book is used for all of them so the Bigram table indicator (A-J) would be the same regardless of the net. However, each net has it's own actual Bigram tables, so you would need to know on which net the message will be sent to encrypt and which net the message was received to decrypt, correct??
When this was in actual use, was that Net identifier ever included as part of the message or was it just "obvious" (based on the frequency it was sent or other specific factors regarding the actual transmission)?
And if we want to exchange messages with other users of these procedures today (and not via radio), we would need to include the net designation... correct?
Seems to me that if the same bigram tables were used across the different nets, but just having more of them (not just 10), you wouldn't need to do that... decrypting the message indicator groups would then tell you (via the K-book) which net the message was sent from so you would know what settings to use for decrypting the rest of the message.
Just random thoughts that keep me up at night...
-- BJ Backitis (KM4RB) Tampa, FL
"Husband, father, and old school geek... not necessarily in that order"
If you have the time, look at the challenges. You'll notice that the corresponding network is marked different in the book compared to the message. There's a document (at work now, opening stuff here can be interpreted) that links network to message identification.
Here's the part of the document that you'll want:
StageIII –Verify characteristic groupsVerify characteristic groups as follows:Take the row 1 entry AZEJ, and drop the dummy letter A.Open the K-book and scroll back to Teil B, Gruppenliste (Part B, Group List)The groups are in alphabetical order, locate ZEJ.The number 151follows the letter group. Return to the beginning of the K-Book and go to Allotment List Part B (Zuteilungsliste, Teil B) and in the column labeled “Key characteristic group” (Schlüsselkenngruppe), scroll down to the entry that includes Column number 151. Ex. 141 –160. The radio group [TRITON] is listed. This verifies the key to be used.