Uhm, one HUGE problem with that.
If people judge authenticity based on the simple fact that a message is
signed, that's just as useless. Why wouldn't the spoofed email be signed
with somebody else's key, to make it past all those people who merely
check to see if it's signed?
The _only_ way to verify authenticity is to check the signature. By
signing every single email sent, you endanger yourself by allowing your
recipients to judge the authenticity of your emails simply by the
existence of a pgp signature.
Therefore, you should only sign emails that contain information important
enough that verification is necessary, otherwise nobody will check.
Andy
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Andy Dills 301-682-9972
Xecunet, LLC www.xecu.net
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Dialup * Webhosting * E-Commerce * High-Speed Access
Which is why the "web of trust" exists. And why people do keysignings at NANOG
events. And why, at least on my mail client, the signature shows the email
address of its owner. If Scott spoofs and email from me and signs it with his
key, people will notice.
-C
If people judge authenticity based on the simple fact that a message is
signed, that's just as useless. Why wouldn't the spoofed email be signed
with somebody else's key, to make it past all those people who merely
check to see if it's signed?
The _only_ way to verify authenticity is to check the signature.
True enough. But you do significantly raise the bar. It's like putting a deadbolt lock on your front door -- maybe it's locked, and maybe it's not. But it's very presence will tend to deter a certain percentage of attackers.
However, even if the door is locked, we all know that a sufficiently motivated attacker can get past *ANY* lock. If they can't break the lock itself, they break the door. If they can't break the door, they break a window. If they can't break a window, then they break a wall.
But it is a pretty good deterrent for people who just walk around twiddling knobs.
Therefore, you should only sign emails that contain information important
enough that verification is necessary, otherwise nobody will check.
Nope. The only way to make this work is to sign all messages, and all messages that are not signed are automatically suspect. Indeed, even signed messages are at least somewhat suspect, and should always have the signature validated -- modern encryption/keyring management programs should make this fairly easy to make automatically happen by default.
oh. my. god.
just when i thought that the subject line could not get any longer in
this thread.
it's just one of my pointless pet peeves...
deeann m.m. mikula
director of operations
telerama public access internet
http://www.telerama.com * 412.688.3200