Schneier on Security

Clive Robinson • January 19, 2018 12:08 PM

@ Tatütata,

The epilogue sequence is played on a Teletype model 35, a machine initially developed for the Bell System around 1960.

I remember the ASR35’s and KSR35’s (the later ASCII 7 hole tapes).

Well I bashed the cr4p out of them five days a week around three hours a day in the 1970’s when doing the programing thing. Oh trivia time 😉 Unix terminals are called “tty” as short hand for teletype.

The thing is back in those days due to bashing the keyboard fifteen hours a week you developed muscles in the arms and shoulders that made you look like a jock not a nerd. As long as you kept your mouth closed and smiled and nodded a lot and just said Hi etc you could get away with not having to stick a jock head first down the loo and swirly him to make a point that brains and brawn were not mutually exclusive (though trying to put that in words to them such that they could comprehend it was such a task that three or four swirlies were quicker 😉

Then when wearing the green I had to use/support/repair “proper” teletype terminals that were TEMPEST hardend and guaranteed to give you a double hernia and three slip disks if you were daft enough to try moving them on your own.

As they were F&CO usage, they had to be mains frequency independent, and two essential items in your repair kit was a large packet of “Blue Rizzler Cigarette Papers” and a tuning fork… Because they had a clutched motor to do the timing. It had enough power to strip the flesh from a finger bone if you were not carefull. It happened to Smudge one of the telemech Sgts and there was ketchup all over the place, which it took three of us to clean up. When he got back from hospital after they had sewn it back together he joked his wife would not be happy as he would not have to do the dishes for a month. The FoS however walked in as Smudge was looking at the teleprinter that bit him, and with out a word put a four pound lump hammer on the bench beside it nodded and walked out. To give Smudge his due he fixed it rather than beat the cr4p out of it…

Oh and the US did not use Baudot –nobody ever did with a teletype– but ITA1 and Murray code. There were important differences of which moving “null” to the zero position was the most important[1] difference. Western Union used Murray through to the 1950’s and the US MIL and NATO may still be using it… They still use the BID1100 crypto kit which was designed for 5 symbol codes.

As for Murray code the CCITT made it ITA2 back in the 1920’s and it hung in till ASCII poped up on the early 60’s it’s still used for RTTY by Hams and others and in weather messaging systems with an extended error correction system. And yes I’ll be using it over the weekend if conditions are right, some still favour HF to the Internet 😉

Back when ASCII started to rear it’s little head there were all sorts of things to be considered and somebody wrote a book over three hundred pages about such codes… It’s the sort of read that needs a double espresso for every chapter 😉

If people are having trouble sleeping I can dig out a refrence to a PDF of it 0:)

[1] The reason to have the null at zero was twofold. The first was null was used to send sync signals when messages were not being sent, but any value could have been used for null. The second reason became quite important which was for use with early stream crypto equipment. The ITU had long befor that set an edict that all Enciphered messages had to be sent and five character words of all upper case alphas seperated by a space and two spaces after every fifth group, ten groups to a line Thus if the addition of a key and Alpha exceeded an alpha value the null (key stream char) was sent instead…

Clive Robinson • January 20, 2018 10:43 PM

@ mostly harmless, Tatütata,

I forgot to mention if you look on page 62, you get info on CCITT ITA2/#2 with some half truths and the reason for an oddity or two with why preables were sent.

Firstly, the NUL is incorrectly identified as not used, and the date of the CCITT code given as ten years after it was started to be looked at.

If you have a hunt around you will find that Vernam’s pattent was 1919 and CCITT unofficialy kicked out a notification in 1920…

Oh and the oddity of preambles sent by operators of

1, Five or more NULs
2, Two FSs (Figure Shifts)
3, One LS (letter shift)

The NULs served as “sync ups” the two Figure Shifts would put the receiving terminal into the Figures State/Mode with the Letter Shift finaly putting the receiving terminal in Letters State/Mode.

The problem was that as the TX operator you would not know what state the RX terminal was in Letters/Figures. If you look at the table you will see that in Letters Mode the LS key actually acts as a delete key and thus could cause problems with back stepping the print head before the first position on the line… But in both Letters and Figures Modes the FS key would set the mode to Figures, thus the sending of the following LS did not cause problems.

Oh you will also see the next code is the “Stretch Code” which was used on the IBM Super Computer known as the “Strech”. You can see from that code –it has no NUL at position zero– many people were unaware of what the likes of the NSA were upto including the IBM designers of the stretc, who though it’s “secret” use would be for designing nuclear bombs not cryptanalysis, and that secret was maintained untill much much later.

In fact the book appears silent on saying that certain code features were actually for “cipher reasons” that were “dressed up” as something else… It shows just how long the various standards organisations got “finessed” by what we would now call the SigInt agencies. In the case of codes since atleast World War One a century ago, if not earlier.

In fact if you look hard enough you will find in the various National Archives, the threads of colaboration back in WWI amongst the then allies that would come the wind down of WWII in Europe give rise to the BRUSA letter. That in turn gave rise to the Five-Eyes, for which you can soundly blaim the English.

It was the English Who had already started “finessing” International Standards Bodies via their General Post Office and Broadcasting Body (BBC) representitives. Before Henry L. Stimson killed off the American “Black Chamber” Herbert O. Yardley had set up in 1919.

As I get older for some reason I find the skullduggary of this hidden and “most secret” world more and more fascinating. Thus can get a tangible feel for why those that had frequented Room 40 of the Admiralty building in London during WWI felt betrayed by Winston Churchill and his memoir of his time as first Sea Lord in WWI which described what Room 40 had been all about.