Im concerned that relay's are unable to authenticate the originators
of messages in MIME/PEM when the messages are encrypted to protect
private data. This is a big change to PEM which I believe deserves
a section in the MIME/PEM document to justify or admit the change.
Why do you see this as a "big change" rather than an addition?
If you are using X.509 certificates (as in current PEM), relays are just as
able to authenticate both the originator and recipient as they are in Classic
PEM. If you are operating a relay, you are certainly able to enforce a
continuation of this policy (example: "relay X will reject any mail not signed
with an X.509 certificate rooted at such-and-such a PCA"). If you are not
currently authenticating originators, there is likewise no change.
The fact that MIME/PEM can be used in other policy environments in no way
prevents it from being used in all of the policy environments currently in use
by Classic PEM implementations, and with the same certificates and PCAs.
In fact, it looks like relays should be able to convert between RFC 1421 and
subsets of MIME/PEM (namely, text-only messages in US-ASCII) without
cryptographic operations. This would provide a gradual upgrade path for
environments containing mixed MIME & non-MIME email software, such as NASA.
Amanda Walker
InterCon Systems Corporation