Schneier on Security

Clive Robinson • October 25, 2010 8:06 AM

When I have time I’ll troll through the list to see if there are any early EmSec documents.

What later became TEMPEST started in WWI when it was found that you could eavesdrop on field telephone systems that used such things as phantom signaling etc.

Later in WWII and just after was when TEMPEST got going in earnest when it was discovered you could (amongst other things) strip of a One Time Tape addition to plain text in an online cipher system by observing the hold and release times of the relay via the signal lines and later PSU lines.

It might be old information but sometimes there are little nuggets to be found that can be revealing as to what people where thinking / investigating at the time.

Clive Robinson • October 26, 2010 3:30 PM

@ Matt,

“1) Physical deterioration of storage media and devices

2) Digital data that cannot be interpreted easily because both the original software and file format descriptions are lost”

Issue (1) is as you say not an issue if you migrate your data. However older media (pre optical media prior to CDROM) is a lot more robust than many people think. Firstly because the bit density is quite low and stored in MFM&RLL format and does not suffer from the clever encoding issues used to get higher bit densities in later times.

Issue (2) is more interesting you have to think back to the early days and just how expensive even low cost storage media was per byte. For instance my 20Mbyte (yes really 20,000,000) HD for my Apple ][ cost more than the rest of the system and would be the equivalent of 20,000USD in todays money or about 1/3 of a years takehome income.

At that sort of cost each byte had real tangable cost, so saving every bit possible was a worth while excercise. I have in my possession a paper from the early 1960’s that discusses minimal date storage and the future issues that we later called Y2K…

However the data encoding was generaly simple to understand such that it could be “hand worked” backwards if the media went bad.

This alows many old file formats (WordStar VisiCalc etc) to be easily understood. Thus the data is still either directly usable or atleast get easy access to the raw content.

That was untill Bill Gates threw the toys out the pram over what he saw as people stealing his property (for which there is evidence that he actually nicked it from elsewhere).

He was laughed at and derieded and it was probably at this time when most data storage formates where relativly simple and well known/documented he decided to cross over to the darkside 😉

Billy boy decided on “locking in” with highly obsficated file formats to effectivly lock up peoples data and keep them dependant on MS and it’s frequent updates which almost always changed the data file format (try loading a Word 4.3 doc in later versions to see this). Oh and of course he continued to keep taking the work of others and re-branding it and knocking it out at high cost (look at all the early MS network code taken from BSD etc) and screaming blue murder when people ignored the outrageous “licence agrements”. This gave rise to much of the later protection mechanisms that people then spent much time and effort breaking or obviating.

Even now MS take (Kerberos for instance) and extend in some way to make it effectivly proprietary and when that fails they try other tricks (such as nobling standards organisations), all of which makes life extreamly difficult for data preservers.

Clive Robinson • October 31, 2010 1:44 PM

@ JT,

“Special Fish Report?”

Yup…

Without actually seeing the document concerned I’m assuming it is from the WWII work at Bletchly Park about a German electromechanical teleprinter stream cipher system designed and manufactured by Lorenz. Which if I remember correctly was a “high command” system that was supposed to be even more secure than Enigma in that it’s maximum message length was many times longer and thus could be used for sending strategic battle orders etc etc.

The name “Fish” just happened to be the Ultra Code Word used by the British for the then compleatly unkown system.

Againif I remember correctly it was broken by William Tutt and was a quite astounding piece of work, that gave rise to the work carried out by Tommy Flowers to build the worlds first programable system usuing valves which we now know as “Colossus”.

The “break” into the unknown system came about due to a simple but fatal “opperator error” by a German telegraphist on a very long (more than four thousand charecter message).

One of the “golden rules” about stream or addative ciphers is NEVER EVER use the same key twice (and a lesser rule is never send the same plaintext under a different key).

Basicaly the German operator sent the long message and started it with the equivalent of “Message Number”. However the operator at the far end after receiving over four thousand charecters sent back a message saying effectivly “Message received incorrectly resend”.

The German operators then made an operational error of reseting the stream start position not renegotiating a new start position and the sending German operator made the fatal mistake of this time sending “Message Nr” not as he originaly sent “Message Number”.

This gave two copies of the same long message under the same key but from the Number/Nr initial difference at slightly different offsets.

This gave a long “message in depth” that allowed the plain text to be removed and a long copy of the key stream was revealed.

Due to a poor deign by Lorenz, William Tutt was able to work out the individual bit cycle lengths they had used and then reconstruct the stream generator pattern.

A mechanical analogue of the stream generator not to disimilar to the Enigma “bombe” system designed by Alan Turing was proposed. However Tommy Flowers from the Post Office research lab at Dollis Hill in London managed to persuade those in charge he could do it reliably with valves (which everybody else assumed from practical experiance where to unreliable).

The end result was the Colossus system, and it did end up with one part of it being unreliable, not the valves but the “tape tractor” used to run the ciphertext through the system. In order to keep up with the valves the tape system used an optical tape reader which was run a lot faster than it was originaly designed to. The result was friction in the tape tractor caused the tape to sometimes catch fire…

Remarkably this break of Fish was done around two and a half years before the allies ever saw the German system or even knew who had manufactured it, and the whole break was done by hand by William Tutt from just that one initial but fatal mistake by the (unknown) German telegraphist.