Sending Encrypted Messages in Morse Code.

Started by gil, August 15, 2012, 10:54:01 AM

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With this entire FASCINATING discussion, there are two , basic,  questions:

"What is your threat model?"
and "
"What information are you transmitting/receiving?". 

If you need to work against a major national power during time of war, it's entirely different from working against your neighborhood kid with a radio scanner. If the information you're passing would fit on a sticky note, a short text encryption method, using paper and pencil is fine.  OTOH, if you're sending 2 megs of battle plans in PowerPoint,also against a nation's security apparatus, that's an entirely different problem.

For the low level survivor coordinating with similar groups, against a nation state enemy with significant electronic warfare capabilities (Ukraine vs Russia), messages need to be short, extremely secure and rarely transmitted. The system keys must be 'incoherent' that is to say random and NOT REPRODUCABLE.  A major killer of intel agent networks in WW II was decrypting back traffic.  If England dropped - Agent A - into France to set-up a resistance organization, safe houses and perons of contact, then he transmitted that all back to England using a MEMORIZED key, WHEN when the Germans eventually capture England's Agent A, they use "practical cryptanalysis" that is; torture the cipher system details and memorized key ouf of Agent A and roll-up the entire network using his testimony and all back traffic (or, as in the Nederlands, they 'play' the network against England for much of the war.).

If YOU being Agent A can recall the system and it's keys to read back traffic, then it's not a one time pad.  If you're using a book, periodical or The Bible for key material, it's not a one time pad. 

So - for a pencil and paper, one time pad it's best used for :
1. Highest security requirement for never being broken.
2. Low volume of traffic, all text.
3. Once the key is destroyed, there is essentially zero opportunity to read actual back traffic.

Remember, if you use a system where you or anyone else can memorize the key, it's not truely a one time pad, for as long as any of you live, and this information will be taken from you by the most extreme means, upon first opportunity of the enemy.

OTOH - I know people so dull, that writing a note in longhand (cursive) might as well be enciphered, because they're functionally illiterate...

73 de RadioRay  ..._ ._

"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry