Date: Fri, 11 Feb 1994 13:33:27 -0500
From: James M Galvin <galvin(_at_)tis(_dot_)com>
In TIS/PEM, a communicant's key is trusted by the user setting the flag
for the certificate containing it.
A communicant's key is always trusted by its issuer, otherwise the issuer
wouldn't be creating the certificate.
Now, it isn't that far a stretch to suggest that a user setting the
designated valid flag for a certificate is "issuing" it and, as such,
the user is responsible for determining that the information in a
certificate is valid before setting the flag, just as an issuer must do
before creating a certificate.
No, there's a difference between the two.
In the first, anyone who has access to the TIS/PEM key database can
modify it, set the "designated valid bit" and spoof you out.
In the second case, since you are creating and signing a certificate,
only somone who has access to your private key can compromise you in
this fashion. When you validate the certificate chain, the last
certificate you verify is your own, instead of checking some magic bit.
This means that my public key database can be moved around freely
without worrying about tampering, since *all* of the information is
self-verifying.
Personally, I much prefer the second solution (which is used by both
RIPEM and PGP, by the way).
- Ted