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| From | Max <maxturv26@gmx.net> |
|---|---|
| Newsgroups | sci.crypt |
| Subject | Re: CHAL2X |
| Date | 2021-09-26 14:40 +0200 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <sippop$1ntf$1@gioia.aioe.org> (permalink) |
| References | <sii6pv$dqc$1@dont-email.me> <sio2rk$urf$1@gioia.aioe.org> <sio3fk$n34$1@dont-email.me> <sio98g$1a3f$1@gioia.aioe.org> <sip27f$pk2$1@dont-email.me> |
On 26.09.21 07:59, Richard Heathfield wrote:
> On 25/09/2021 23:53, Max wrote:
>> On 25.09.21 23:14, Richard Heathfield wrote:
>>> On 25/09/2021 22:03, Max wrote:
>>
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>> ######################################################
>> # #
>> # POSSIBLE SPOILER AHEAD! #
>> # #
>> ######################################################
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>> ######################################################
>> # #
>> # POSSIBLE SPOILER AHEAD! #
>> # #
>> ######################################################
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>>>> Also, this difference stays the same for two consecutive characters.
>>>
>>> I have no idea why that might be. My algorithm did nothing special
>>> for two consecutive characters. I conclude that you've done your
>>> Bright Eve[1] thing again and have not discerned my algorithm,
>>> although you're obviously quite close.
>>>
>>> [1] Not *that* bright. :-) This was solvable using standard
>>> techniques to be found in any cryppie's kitchen drawer, and I have no
>>> doubt that's how you did it. The one I *was* going to post was more
>>> of a bitch but I ran out of wossname, motivation to code it up.
>>>
>>
>>
>> Of course. Just by the book (this time the "and"s, not the "the"s).
>> Yet, do you really think, it is possible to find the algorithm before
>> finding the plaintext? While some person smarter than me might just
>> eyeball the CHATX algorithm from the ciphertext, I don't see how this
>> could be done here.
>
> You think I'm being a bit tight? You're probably right. I think on
> reflection(!) I should have given it to you when you talked about
> nybbles being mirror images, even though nybbles had no part of the
> algorithm.
No, no, everything is cool. I just thought, it is more fun to not just
spit out a solution but to discuss the thought process and stuff.
How would you have approached this? Is there a way to go for the
algorithem/cipher without getting a pair of plaintext/ciphertext first?
>
> It was pure bit reversal of the middle six bits of each octet:
Ok, so you reversed the order of the bits AND inverted them. I might
should have seen that, but I didn't. Let's see if others do.
>
> while((ch = getchar()) != EOF)
> {
> int i;
> bi = (unsigned char)ch;
> bo = (unsigned char)ch;
> for(i = 1; i < 7; i++)
> {
> int j = 7 - i;
> if(BIT_QRY(p, i))
> {
> BIT_CLR(q, j);
> }
> else
> {
> BIT_SET(q, j);
> }
> }
> putchar(bo);
> }
>
>
> I left the high bit alone so that ASCII would stay ASCII, and so I left
> the low bit alone for symmetry. I'd have posted the ciphertext as ASCII
> were it not for the fact that I was getting a lot of backspaces in the
> ciphertext, which I thought might confuse the issue.
>
Thanks again for another puzzle. It would be interesting to find a
puzzle that is not a classic hand cipher (substitution, transposition),
yet breakable, e.g. by differential cryptoanalysis with "small" amounts
of ciphertext (like 1,000 bytes).
Cheers,
Max
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CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-23 16:34 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-25 19:45 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-25 19:04 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-25 20:08 +0200
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-25 23:03 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-25 22:14 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 00:53 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 06:59 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 14:40 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 13:58 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 15:54 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 15:06 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 17:11 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 16:53 +0100
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 17:12 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 18:42 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 18:27 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 20:43 +0200
Re: CHAL2X Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-26 20:41 +0100
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 21:46 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 20:57 +0100
Re: CHAL2X Stefan Claas <spam.trap.usenet@gmail.com> - 2021-09-26 13:19 -0700
Re: CHAL2X Max <maxturv26@gmx.net> - 2021-09-26 22:30 +0200
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 21:37 +0100
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 21:33 +0100
Re: CHAL2X Stefan Claas <spam.trap.usenet@gmail.com> - 2021-09-26 13:39 -0700
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-26 20:53 +0100
Re: CHAL2X Colin <a@b.com> - 2021-09-27 19:11 +1300
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-27 07:41 +0100
Re: CHAL2X Colin <a@b.com> - 2021-09-27 20:02 +1300
Re: CHAL2X Richard Heathfield <rjh@cpax.org.uk> - 2021-09-27 08:27 +0100
Re: CHAL2X Colin <a@b.com> - 2021-09-28 20:09 +1300
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