Hi all,

a couple of days I came across a posting from user yeti
and found his usage of dc very cool.

$ dc -e
'127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
P'

https://github.com/stefanclaas/str4dc

Regards
Stefan

Stefan Claas <stefan@mailchuck.com> writes:

> a couple of days I came across a posting from user yeti
> and found his usage of dc very cool.
>
> $ dc -e
> '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
> P'

Cool how? It's a curious arithmetic operation, but I can't think of a
use for it. Do you have one?

(It would be helpful, though not that important in this case, if you
could post code without additional like breaks.)

--
Ben.

Ben Bacarisse wrote:

> Stefan Claas <stefan@mailchuck.com> writes:
>
> > a couple of days I came across a posting from user yeti
> > and found his usage of dc very cool.
> >
> > $ dc -e
> > '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
> > P'
>
> Cool how? It's a curious arithmetic operation, but I can't think of a
> use for it. Do you have one?

When I saw the posting from the author I thought it might be a nice
trick to encode messages, similar to SCOS, assumed other reader circles
do not know how this was done.
> (It would be helpful, though not that important in this case, if you
> could post code without additional like breaks.)

Ok.

Regards
Stefan

Stefan Claas wrote:

> Ben Bacarisse wrote:
>
> > Stefan Claas <stefan@mailchuck.com> writes:
> >
> > > a couple of days I came across a posting from user yeti
> > > and found his usage of dc very cool.
> > >
> > > $ dc -e
> > > '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
> > > P'
> >
> > Cool how? It's a curious arithmetic operation, but I can't think
> > of a use for it. Do you have one?
>
> When I saw the posting from the author I thought it might be a nice
> trick to encode messages, similar to SCOS, assumed other reader
> circles do not know how this was done.

By omitting the dc command line and only posting the string.

Regards
Stefan

Stefan Claas <stefan@mailchuck.com> writes:

> Ben Bacarisse wrote:
>
>> Stefan Claas <stefan@mailchuck.com> writes:
>>
>> > a couple of days I came across a posting from user yeti
>> > and found his usage of dc very cool.
>> >
>> > $ dc -e
>> > '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
>> > P'
>>
>> Cool how? It's a curious arithmetic operation, but I can't think of a
>> use for it. Do you have one?
>
> When I saw the posting from the author I thought it might be a nice
> trick to encode messages, similar to SCOS, assumed other reader circles
> do not know how this was done.

Since you didn't link to (or, better yet, reply to) the post in
question, I have no idea what you are talking about.

--
Ben.

Ben Bacarisse wrote:

> Stefan Claas <stefan@mailchuck.com> writes:

> > When I saw the posting from the author I thought it might be a nice
> > trick to encode messages, similar to SCOS, assumed other reader
> > circles do not know how this was done.
>
> Since you didn't link to (or, better yet, reply to) the post in
> question, I have no idea what you are talking about.

Oh, sorry! I thought you have read the URL in my GitHub repository ...

Here is the URL again:

https://www.unitedbsd.com/d/864-beware-of-dc-version-differences

Regards
Stefan

Stefan Claas <stefan@mailchuck.com> writes:

> Ben Bacarisse wrote:
>
>> Stefan Claas <stefan@mailchuck.com> writes:
>
>> > When I saw the posting from the author I thought it might be a nice
>> > trick to encode messages, similar to SCOS, assumed other reader
>> > circles do not know how this was done.
>>
>> Since you didn't link to (or, better yet, reply to) the post in
>> question, I have no idea what you are talking about.
>
> Oh, sorry! I thought you have read the URL in my GitHub repository ...

Why would I? You posted a dc command and a link. There's
nothing tempting me to follow the link.

> Here is the URL again:
>
> https://www.unitedbsd.com/d/864-beware-of-dc-version-differences

Still no idea what you are talking about but I admit I did not read all
the posts. I did not learn anything from that thread that I did not
learn from your initial post. I did not know about this curious (and
undocumented) behaviour until you posted, but I can't see much
connection to sci.crypt.

By the way, that behaviour goes all the way back to early versions (from
the 1970s) of Unix, but is not documented anywhere.

Also of note (to me) is that bc (once a dc pre-processor, now often a
stand-alone program) does not behave the same way, and the behaviour is
explicitly undefined by POSIX. Also, POSIX does not define dc so it
might not be a good idea to rely on it being available everywhere.

--
Ben.

Ben Bacarisse wrote:

> Stefan Claas <stefan@mailchuck.com> writes:
>
> > Ben Bacarisse wrote:
> >
> >> Stefan Claas <stefan@mailchuck.com> writes:
> >
> >> > When I saw the posting from the author I thought it might be a
> >> > nice trick to encode messages, similar to SCOS, assumed other
> >> > reader circles do not know how this was done.
> >>
> >> Since you didn't link to (or, better yet, reply to) the post in
> >> question, I have no idea what you are talking about.
> >
> > Oh, sorry! I thought you have read the URL in my GitHub repository
> > ...
>
> Why would I? You posted a dc command and a link. There's
> nothing tempting me to follow the link.
>
> > Here is the URL again:
> >
> > https://www.unitedbsd.com/d/864-beware-of-dc-version-differences
>
> Still no idea what you are talking about but I admit I did not read
> all the posts. I did not learn anything from that thread that I did
> not learn from your initial post. I did not know about this curious
> (and undocumented) behaviour until you posted, but I can't see much
> connection to sci.crypt.

If someone had posted a much longer string, for dc usage and I had
not posted this, I guess people may had used a hex editor to look at
the content, an then see garbled characters. So it can be used as an
encoder, which people might not be aware of, or obfuscation scheme, I
would say.

> By the way, that behaviour goes all the way back to early versions
> (from the 1970s) of Unix, but is not documented anywhere.

Ah.
> Also of note (to me) is that bc (once a dc pre-processor, now often a
> stand-alone program) does not behave the same way, and the behaviour
> is explicitly undefined by POSIX. Also, POSIX does not define dc so
> it might not be a good idea to rely on it being available everywhere.

Yes, I understand.

Regards
Stefan

Stefan Claas <stefan@mailchuck.com> writes:

> Ben Bacarisse wrote:
>
>> Stefan Claas <stefan@mailchuck.com> writes:
>>
>> > Ben Bacarisse wrote:
>> >
>> >> Stefan Claas <stefan@mailchuck.com> writes:
>> >
>> >> > When I saw the posting from the author I thought it might be a
>> >> > nice trick to encode messages, similar to SCOS, assumed other
>> >> > reader circles do not know how this was done.
>> >>
>> >> Since you didn't link to (or, better yet, reply to) the post in
>> >> question, I have no idea what you are talking about.
>> >
>> > Oh, sorry! I thought you have read the URL in my GitHub repository
>> > ...
>>
>> Why would I? You posted a dc command and a link. There's
>> nothing tempting me to follow the link.
>>
>> > Here is the URL again:
>> >
>> > https://www.unitedbsd.com/d/864-beware-of-dc-version-differences
>>
>> Still no idea what you are talking about but I admit I did not read
>> all the posts. I did not learn anything from that thread that I did
>> not learn from your initial post. I did not know about this curious
>> (and undocumented) behaviour until you posted, but I can't see much
>> connection to sci.crypt.
>
> If someone had posted a much longer string, for dc usage and I had
> not posted this, I guess people may had used a hex editor to look at
> the content, an then see garbled characters. So it can be used as an
> encoder, which people might not be aware of, or obfuscation scheme, I
> would say.

I see. You propose this as a mild obfuscation. Might have been fun to
have posted it as challenge since the groups have been very quiet of
late.

There are probably other "look like hex" encoding that are harder to
spot and simpler to generate. Relying on dc to partly decode it is not
adding much to my mind.

--
Ben.

Ben Bacarisse wrote:

> Stefan Claas <stefan@mailchuck.com> writes:

> > If someone had posted a much longer string, for dc usage and I had
> > not posted this, I guess people may had used a hex editor to look at
> > the content, an then see garbled characters. So it can be used as an
> > encoder, which people might not be aware of, or obfuscation scheme,
> > I would say.
>
> I see. You propose this as a mild obfuscation. Might have been fun
> to have posted it as challenge since the groups have been very quiet
> of late.
>
> There are probably other "look like hex" encoding that are harder to
> spot and simpler to generate. Relying on dc to partly decode it is
> not adding much to my mind.

Well, this was simpler to generate and convert back:

93 10 1F 1F 1C 7A 22 1C 27 1F 19 7B 78 09 13 14
28 0C 14 28 7E 1D 20 28 29 8D 16 7C 28 14 1A 25
1F 10 7A 29 10 28 29 7B 03 23 78 73 74 79 70 76

Maybe to easy to solve, for the community.

Regards
Stefan

Stefan Claas wrote:

> Ben Bacarisse wrote:
>
> > Stefan Claas <stefan@mailchuck.com> writes:
>
> > > If someone had posted a much longer string, for dc usage and I had
> > > not posted this, I guess people may had used a hex editor to look
> > > at the content, an then see garbled characters. So it can be used
> > > as an encoder, which people might not be aware of, or obfuscation
> > > scheme, I would say.
> >
> > I see. You propose this as a mild obfuscation. Might have been fun
> > to have posted it as challenge since the groups have been very quiet
> > of late.
> >
> > There are probably other "look like hex" encoding that are harder to
> > spot and simpler to generate. Relying on dc to partly decode it is
> > not adding much to my mind.
>
> Well, this was simpler to generate and convert back:
>
> 93 10 1F 1F 1C 7A 22 1C 27 1F 19 7B 78 09 13 14
> 28 0C 14 28 7E 1D 20 28 29 8D 16 7C 28 14 1A 25
> 1F 10 7A 29 10 28 29 7B 03 23 78 73 74 79 70 76
>
> Maybe to easy to solve, for the community.

Same procedure, but other output format and with
shorter plain text encoded:

09131079262014181b8e17271f221e0c111f23701a201d25282b1f211027
8f2913107a1c162a248f191f127e

Regards
Stefan

Stefan Claas <stefan@mailchuck.com> writes:

> Hi all,
>
> a couple of days I came across a posting from user yeti
> and found his usage of dc very cool.
>
> $ dc -e
> '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
> P'

dc -e'[[dc -e]PA06FPP8DP[dx]P39PAP]dx'

Phil
--
We are no longer hunters and nomads. No longer awed and frightened, as we have
gained some understanding of the world in which we live. As such, we can cast
aside childish remnants from the dawn of our civilization.
-- NotSanguine on SoylentNews, after Eugen Weber in /The Western Tradition/

On 12/10/2023 11:18 pm, Phil Carmody wrote:
> Stefan Claas <stefan@mailchuck.com> writes:
>
>> Hi all,
>>
>> a couple of days I came across a posting from user yeti
>> and found his usage of dc very cool.
>>
>> $ dc -e
>> '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
>> P'
>
> dc -e'[[dc -e]PA06FPP8DP[dx]P39PAP]dx'

....to quine a phrase.

--
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

Phil Carmody wrote:

> Stefan Claas <stefan@mailchuck.com> writes:
>
> > Hi all,
> >
> > a couple of days I came across a posting from user yeti
> > and found his usage of dc very cool.
> >
> > $ dc -e
> > '127912987AD86EB9688CCAC88D7338BD87FEC65023344971356EFEF999778D7448AAEC6528A
> > P'
>
> dc -e'[[dc -e]PA06FPP8DP[dx]P39PAP]dx'

Cool! :-)

Regards
Stefan

Stefan Claas wrote:
> Same procedure, but other output format and with
> shorter plain text encoded:
>
> 09131079262014181b8e17271f221e0c111f23701a201d25282b1f211027
> 8f2913107a1c162a248f191f127e

$ tr 'A-F0-9' 'D-FA-C5-90-4' < msg.txt | xxd -r -p

Regards
Stefan