[Christmas Challenge 2024] Crack Doppelkastenschluessel-Hex

Post by Stefan Claas
Hi all,
I recently finished my Doppekastenschluessel-Hex project,
which is a simplified version of the original German WWII
cipher, with hex notation.
For more details check my previous thread 'Seriation'
Your task is to crack the provided message, which uses
only one key for encryption, instead of two (default)
or more.
75 A2 85 D1 84 59 85 2D 25 CB 85 1C 24 70 27 6C
C5 3C 65 2E 87 6C 8E E7 89 E9 C9 3E 8E 7D 8E D6
Please note: The message is written as normal text and
not like plaintext messages from the old days and with
padding applied.

Perhaps we need a larger amount of ciphertext?

Anyway, Merry Christmas!

Post by Stefan Claas
The price for the Winner is a set of EFF lapel pins and
an orginal sticker for the 'age' encryption file program
and for the Runner-Up an 'age' file encryption sticker.
<https://1drv.ms/i/s!AjK3D2S6tPVNgSvTOonKu70ci9aX?e=KMZCdb>
Send your decrypted result to sacenator<at>gmail<dot>com
and do not post your result here.
Merry Christmas
Stefan

Stefan Claas

2024-12-20 20:51:11 UTC

Perhaps we need a larger amount of ciphertext?

That would make cryptanalysis easier, right?

BTW. For drawing the winners, should they been drawn from
a random pool of entries, or by first come first serve?

--
Regards
Stefan

Chris M. Thomasson

2024-12-20 21:00:30 UTC

Perhaps we need a larger amount of ciphertext?

That would make cryptanalysis easier, right?

I think so. Depends on the algorithm. If it's secure than perhaps no so
much... The interesting aspect of SCOS is that it's not secure at all.

Post by Stefan Claas
BTW. For drawing the winners, should they been drawn from
a random pool of entries, or by first come first serve?

That is up to you! :^)

Stefan Claas

2024-12-20 21:10:44 UTC

Post by Chris M. Thomasson
Perhaps we need a larger amount of ciphertext?

That would make cryptanalysis easier, right?

I think so. Depends on the algorithm. If it's secure than perhaps no so
much... The interesting aspect of SCOS is that it's not secure at all.

Well, only one key is used and it is a double square cipher, i.e. it is
basically a monoalphabetic bigraphic bipartite substitution, according
to Wikipedia.

Post by Stefan Claas
BTW. For drawing the winners, should they been drawn from
a random pool of entries, or by first come first serve?

That is up to you! :^)

O.k. :-) Should there be many entries, I choose random and if
it's only a couple of entrie by first come first serve.

--
Regards
Stefan

Chris M. Thomasson

2024-12-20 21:39:25 UTC

Post by Chris M. Thomasson
Perhaps we need a larger amount of ciphertext?

That would make cryptanalysis easier, right?

I think so. Depends on the algorithm. If it's secure than perhaps no so
much... The interesting aspect of SCOS is that it's not secure at all.

Well, only one key is used and it is a double square cipher, i.e. it is
basically a monoalphabetic bigraphic bipartite substitution, according
to Wikipedia.

Another aspect of SCOS. Richard wanted us to derive an algorithm. If not
just outright copy his C impl which he encrypted and posted. I pissed
him off a bit in that thread. Sigh. Damn!

Post by Stefan Claas
BTW. For drawing the winners, should they been drawn from
a random pool of entries, or by first come first serve?

That is up to you! :^)

O.k. :-) Should there be many entries, I choose random and if
it's only a couple of entrie by first come first serve.

Sounds good!

Fwiw:

http://fractallife247.com/test/hmac_cipher/ver_0_0_0_1?ct_hmac_cipher=fe7ba1c3a324cb23d2f9c6d4b723f882c2ff8e86d1a2fbe3a6bd75f7f703b18fe39e263285743cf854aea3f6e9d84fc985daee13faa338fae791ab7f672979bd24c173e9a75c7f2c6dba6c1335b70b0a209dd5d39ad751c0649b0f5eb795783e7b8c336db178224e098313d9de8972c5a75601aab74f3ebb7c9ccdf8dd99c507b194f230ec87ab5771a6ddd56ddcd793fdc5c61551ee64b977f76390062c0f91832ae4368c3ad6684f29e1ec45c61de3edbf2ee9116e9806292231090ff13e1a753ce12f48617c9c6cf6a934df55807875f44bbac91166c1f9a1afc7e8fbe69b9e94ab168b82f6b96bdb8fd00f8ddfdf722a50656fea6c08d1b4519988faf7594697db153a0b8d07faa6a2bd425a59b0e24eddea917c5e1092b29c5df031db212541d5559a632f925aa94e72eb3c8641634dde3197b28bcde0637c76a15ebc79e7e32746dc2ba45676f99540883b2bdf9693f128a7c9f0c16b8e143e6487c8c390b5c9c15bc505ffdf7062322f6a37d915c2928048101d987ed9c7fac91cb5868d04df8ff5

The plaintext is:

It's your contest. So, do with it as you will. Fwiw, I am getting very
busy with family and well, it's that time of year. Ho ho ho! ;^)

My test here is too complicated for a fun little contest. It actually
might be "secure". Wel, some other people think that it just might be,
secure. Strange!

Anyway, merry christmas!

:^)

Stefan Claas

2024-12-20 21:51:35 UTC