Are ++ and -- operators really more efficient

[Mark Wooding]

News uses the _exact_ same format as mail, with only a few minor
differences in the headers.

Would you like to provide a reference for that claim, say, to an RFC?

RFC1036 describes a number of quite nontrivial differences in header
format between mail and news. For example, news headers cannot contain
comments (but `[email protected] (Natural Name)' is specially allowed as
a `From' address).

Son-of-1036 -- a long-expired Internet Draft, but still influential --
implies that MIME should be adopted but does not include MIME-Version in
either its list of mandatory or optional headers.

Attachments are unwelcome in most groups outside alt.binaries,

.... and this is precisely the format of S/MIME and PGP/MIME signed
messages.

-- [mdw]

 

[Richard]

News uses the _exact_ same format as mail, with only a few minor
differences in the headers.

Would you like to provide a reference for that claim, say, to an RFC?

RFC1036 describes a number of quite nontrivial differences in header
format between mail and news. For example, news headers cannot contain
comments (but `[email protected] (Natural Name)' is specially allowed as
a `From' address).

Son-of-1036 -- a long-expired Internet Draft, but still influential --
implies that MIME should be adopted but does not include MIME-Version in
either its list of mandatory or optional headers.

Attachments are unwelcome in most groups outside alt.binaries,

... and this is precisely the format of S/MIME and PGP/MIME signed
messages.

-- [mdw]

I am beginning to think he is purposely misinforming people. Claims that
recursion is always easier than iteration and that dereferencing the
NULL pointer is "often done" with no side affects make me think SS has
an agenda.

 

[Stephen Sprunk]

I am beginning to think he is purposely misinforming people.

It is not deliberate; at worst, I am wrong, but it is more often the
result of poorly expressing myself.

Claims that recursion is always easier than iteration

For instance, in that case I meant that _for problems that are described
recursively_, one should use recursion. I would never describe stepping
through an array as "access the first element, then step through the
rest of the array" (i.e. recursion); I would describe it as "access the
first element, advance to the next element, repeat" (i.e. iteration)
because it's obviously an iterative problem. Even describing an
iterative algorithm for a post-order tree traversal is difficult,
therefore I would prefer the simpler recursive solution.

and that dereferencing the NULL pointer is "often done" with no side
affects

I never said that; you are confusing me with someone else. My sole
relevant contribution to that discussion was that "if (p)" and "if (!p)"
were common idioms and examples of their use.

make me think SS has an agenda.

My only agenda here is to learn to be a better programmer. If that
means unintentionally exposing my ignorance from time to time, so be it;
unlike many folks, I have no problem being proven wrong about something
and appreciate any (reasonably civil) corrections I receive. Your ad
hominem attack on me, however, is not appreciated.

S

 

[Stephen Sprunk]

Finally, there's another problem which signatures just don't address. I
could, quite easily, start (re-)signing your messages using my key (with
a sock-puppet name attached). There's no particularly interesting
change here -- the credit which should have gone to `Keith Thompson' now
goes to `mdw's sock puppet', but this is a trivial renaming.

.... except that many folks (like me) would see both messages and thus
would know what you are doing and alert others.

But I can do worse: I could also (re-)sign messages from (say) Han from
China (maybe editing them slightly). Now everyone who gets messages
through me (could be quite a lot of people, if I play stupid games with cancel
messages and so on) thinks that their previously reliable source has
become a ghastly troll.

Forgery of cancel messages has led to many news server admins
configuring their servers to simply ignore them; I see hundreds of spams
per day on the various newsgroups I frequent, each accompanied by a
cancel message from a "helpful" bot.

It's a bit far-fetched. But it's still vaguely possible, and there just
isn't any crypto you can use to stop it. Sorry.

S/MIME (or, for that matter, PGP or PGP/MIME) _could_ defeat your
trickery by allowing admins to honor only cancel messages that were
signed by the same key/cert/whatever as the original message. However,
signed messages are still rare, so nobody (AFAIK) has bothered to write
the code to do the necessary checking.

S

 

[Stephen Sprunk]

Would you like to provide a reference for that claim, say, to an RFC?

Both are based on RFC 822.

RFC1036 describes a number of quite nontrivial differences in header
format between mail and news. For example, news headers cannot contain
comments (but `[email protected] (Natural Name)' is specially allowed as
a `From' address).

That's still allowed in mail as well.

Son-of-1036 -- a long-expired Internet Draft, but still influential --
implies that MIME should be adopted but does not include MIME-Version in
either its list of mandatory or optional headers.

RFC 1036 says that RFC 822 controls when they conflict, and RFC 822 has
been updated (via RFC 2822) to include support for MIME, so news
indirectly has official support for MIME as well.

The idea was that news and mail messages could be freely converted back
and forth by gateways by only modifying a few headers, leaving most
headers and the entire body untouched.

... and this is precisely the format of S/MIME and PGP/MIME signed
messages.

"Attachments" (not defined in the relevant RFCs) generally refers to
non-text parts of multipart/mixed messages, though non-text parts of
multipart/related might qualify as well. IMHO, multipart/signed does
not qualify as having "attachments" under any reasonable definition.

S

 

[Stephen Sprunk]

[This subthread is becoming increasingly off-topic for comp.lang.c.
Does anyone have objections to moving it to sci.crypt? I'd do it
unilaterally, but I don't want to leave out people who have incomplete
feeds.]

No objection here; I've added it and set the followup-to appropriately.
Any folks in c.l.c that still care about this subthread can join us
over in sci.crypt.

Yes. The latter's not difficult to arrange. CAs could provide download
services for their customers (and actually earn the money they make).

"Forever" is _very_ difficult to arrange. I can't guarantee I'll be
alive next week, much less ten years from now; how can I guarantee
Thawte (or anyone else) will be serving up my certificate on their web
site then, or even still be in business?

How come you're receiving email or news but don't have a net connection?

Believe it or not, there are folks who still get mail and news via UUCP,
Bitnet, and other non-IP networks. There are also plenty of folks out
there who are behind restrictive firewalls that cannot access arbitrary
web sites.

Even for those of us who have "full" net access, it isn't necessarily
24x7; I often download mail and news before boarding a plane, write
responses en route, and then send them when I arrive at the other end;
if authentication depended on a "live" connection, I wouldn't be able to
verify messages as I read them, making the scheme rather useless.

More importantly, why do you think it's important to verify that a
(particular, named) someone you've never heard of and are never likely
to meet signed a particular message? If you actually have an /a priori/
relationship with someone, you ought to have a means of obtaining a
certificate in advance. If you don't, you might as well be establishing
a very authentic channel with the adversary.

I do business with dozens of people per day that I've never met in
person or even talked to on the phone (and most likely never will).
Assume I have some non-cryptographic way of authenticating them when we
first communicate -- if I need to authenticate them at all, which
sometimes isn't necessary. However, I don't want to (or can't) go
through that every time my phone rings or email dings; knowing the
person X that I authenticated last week is still the same person X is
often valuable, even in cases where knowing the actual identity of
person X doesn't matter.

No. I've given justifications for my claims, and I'm continuing to do
so.

You can justify your opinion all you want, but it's still an opinion.
"Proof by repeated assertion" is not proof, nor can it make an opinion
into fact.

Again, there is /no point/ in establishing secure communications with
someone you have no way of identifying. Here, by `identify', I mean
`match up with some other locally meaningful identifying characteristic'
rather than just coming up with a name. It's interesting to know that a
message was signed by your friend, by a representative of some company
you have or plan to have dealings with, by the author of a book or
paper, etc. It's not useful to know that your message was signed by
someone who might be called `Mark Wooding' or `Falcon Kirtaran' because
that doesn't give you any additional information about who the signer
actually /is/.

There is often a point to that. For instance, imagine a doctor helping
a patient; he is obligated to keep the information confidential, and
part of that may include securing the communications channel, but he
does not need to know the actual identity of the patient (who, due to
his medical condition, wants to remain anonymous). It would be useful,
though, if the doctor could confirm that the patient X calling him today
is (or is not) the same patient X that called last week, so that he
could prevent accidentally disclosing confidential information to
patient Y pretending to be patient X.

Bringing it back to the idea of signing news posts, we recently had an
alleged incident of a troll forging messages from another regular
poster. If he had signed his normal posts, and the forgeries were
unsigned, it would be much easier to believe him. OTOH, he could be
proven a liar if the alleged forgeries were signed with his key. Again,
I don't particularly care about the identity of any given poster; what I
care about is whether two messages came from the _same_ person.

It was standardized for use in email. I'm not aware of an RFC
sanctioning the use of MIME in news articles. RFC1036 is not marked as
updated or obsoleted.

As noted in another message, RFC 1036 says that RFC 822 controls in the
event of a conflict, and RFC 822 has been obsoleted by RFC 2822, which
explicitly mentions support for MIME. To me, that means MIME is
sanctioned for use with news, at least as much as the IETF "sanctions"
anything.

Use in news took much longer, pushed largely by graphical all-in-one-
news/mail clients, and was fought quite vigorously.

.... and futilely. It was inevitable, and even most command-line
newsreaders (which don't do mail at all) implement MIME these days.

I still don't think it's necessarily complete.

The existing specifications are sufficient to implement it properly, and
many folks have, which is the IETF's mission.

Oh -- to me, that's a cryptographic detail. The interesting design
stuff is in the key management, and that's where the two differ.

That "detail" was, I thought, the main point of contention with CBF's
proposal to sign messages with a simple CRC and verify the CRC to
"prove" who sent them

I'm curious what "cruft" it shows you for my signed example message;
my newsreader just puts a little icon in the header bar that shows the
message has a valid signature. Even a non-S/MIME-capable reader
should just show it as an attachment, rather than adding cruft to the
message body.

aptitude install trn2 inn2-inews ... start, find article, ...

It puts a `-=-=-=-=-=-' marker at the top (in standout), and a note

-=-=-=-=-=-
[Attachment type=application/x-pkcs7-signature, name=smime.p7s]
-=-=-=-=-=-

at the bottom (again the markers are in standout). It's certainly less
objectionable than the Kirtaran's PGP cruft (which trn4 shows in full!)
but it's still somewhat annoying. (Standout appears white-on-black,
which is visually distracting.)

Hmm. Well, it's an improvement. I occasionally use a text-based email
program, and it just adds a small indicator that the message has
attachments to the status bar; it doesn't add any cruft to the message
body unless I press a key to see the attachment list.

S

 

[Richard Bos]

Falcon Kirtaran is presumably using an RSA key.

Which, on a programming newsgroup, is excessive. There might be an
excuse for it on soc.legal.advise.getting-out-of-death-row, but not
here.

Richard

 

[Kaz Kylheku]

Which, on a programming newsgroup, is excessive.

The purpose of signing is to make something difficult to repudiate.

Hey may come to regret that he put a difficult-to-repudiate signature to some
of the bullshit he has written.

Especially if the same key is tied to some important documents whose
validity will fall down if any one of them is successfully repudiated.