[GreenKeys] Here's a sweet one on the bay. (crypto machines)

[Christian Gauger-Cosgrove]

On 17 May 2013 14:35, John Nagle <nagle at animats.com> wrote:
>     I've pushed the keys on an Enigma machine.  The keyboard is awful.
> There's about an inch of key travel and you have to push the keys
> really hard, because the rotors are advanced by the key presses.
> Each rotor has 52 big electrical contacts rubbing, (26 on each
> face) so there's a huge amount of friction in the system.
> The only electrical parts are the battery and lamps, and
> a plugboard for some extra cryptographic complexity.  The
> rotor advance sequence is very simple, which is why it's
> not difficult to break its cypher.
>
Its rotor advance does have a few quirks to it. And the four rotor
Kriegsmarine machines add another layer of complexity. But the rotor
advance on that is still the same as on the 3 rotor Kriegsmarine and
Luftwaffe/Heer machines.

The fourth rotor on the Kriegsmarine machine was not stepped; it
basically acted as a movable reflector, as it was designed to fit in
half the space of the normal "wide" reflector; with a new set of
"thin" reflectors in service with those fourth rotors. (Creating in
essence, four movable reflectors of which two setups are compatible
with the old B and C reflectors.)

When used properly; the plugboard on the Enigma made it *EXTREMELY*
more difficult to break.


On the other hand, the major advantage of the Enigma, the fact that
encryption and decryption are the exact same process, means the cipher
is rather weak. in that no letter can encrypt to itself. That, plus
odometer like stepping, and the gradual introduction of advancements
to the Enigma's security made it so the Poles and the UK could read
traffic on it from before the war even started, until the war ended.
(With a few blackout periods, like when the Kriegsmarine decided to be
innovative).


>     Machines with more rotors were built, like the
> T-52 Geheimschreiber, but they needed power drive and
That was a teletype cipher; it also didn't use its rotors as a
scrambling maze. It used its rotors as a way to generate ten rather
random bits. Which -- depending on the model -- were in various ways
to encrypt/decrypt the 5-bit
ITA2/Baudot/Murray/whatever-you-want-to-call-it code. Five bits were
extracted for XORing with the plaintext, and the last five bits were
used to swap some of the bit positions.

The more famous telecipher was the Lorenz Schlusselzusatz 40/42. That
was the one that COLOSSUS was built to break. It used twelve pinwheels
to create five bits to XOR with the plaintext/ciphertext.

The T-52 in its later versions was merry hell to break, but not much
traffic was intercepted for it. ...And since it was used by the
Luftwaffe if I remember correctly, most traffic on it would eventually
get a bit massaged by the German high command staff and turned into
Enigma traffic. The 10 rotors on the T-52 had a fixed, unchangeable
combination of bits on each. A serious security flaw. On the Lorenz
machine, all ofthe pinwheels were settable, so pin combinations on the
wheels changed as part of the key; it was also used in more places
that the UK would find more useful if they could break it.


> were much bulkier.  An Enigma is a little briefcase-sized box
> with a self-contained battery.  Command cars, tanks, and
> submarines carried them.  The bigger machines were for
> fixed installations.
>
>     The M-209 is about as secure as an Enigma, but
Debatable, that claim is. You have to think about the setup of the
M-209s innards, because a bad key means you're doing some easily
breakable ciphering. Whereas the Enigma is somewhat idiot proof in its
key setup. On the other hand, as you mentioned the M-209 could print.
A special addition to the Enigma could let it do so too, but that was
an infrequent device to say the least.

On the other hand, near the end of the war, the Germans had produced a
copy of the M-209; but it never saw very much wide use. (Mostly
because it came around late enough "Hey we have a new cipher devi--
Why does the barracks have an American flag flying over it?")


Now, if you think the M-209 is nice take a look at the C-52, or CX-52;
it came out later (1952 as the model name/number indicates), was
designed by the same company -- Boris Hagelin's Crypto AG -- and is
backwards compatible with the M-209, using the right configuration of
pinwheels and lugs. It was used by a lot of different countries, and
was apparently quite popular for embassy use.



During WWII, the US actually developed the "best" of the rotor cipher
machines; it did require power drive, and was rather large. It was the
SIGABA; which had a grand total of fifteen rotors, which were of the
"Enigma" style wire scrambler rotors. As I mentioned in a previous
e-mail; the SIGABA was not cracked until just a few years ago. At
least publicly; if the NSA found a way to break it, they kept mum
about that.


Cheers,
Christian Gauger-Cosgrove