[Cryptography] PRISM-Proofing and PRISM-Hardening

Phillip Hallam-Baker hallam at gmail.com
Wed Sep 18 09:08:04 EDT 2013

A few clarifications

1) PRISM-Proof is a marketing term

I have not spent a great deal of time looking at the exact capabilities of
PRISM vs the other programs involved because from a design point they are
irrelevant. The objective is to harden/protect the infrastructure from any
ubiquitous, indiscriminate intercept capability like the one Gen Alexander
appears to have constructed.

PRISM-class here is merely a handy label for a class of attack where the
attacker can spend upwards of $100 million to perform an attack which
potentially affects every Internet user. PRISM-class is a superset of

2) SSL is not designed to resist government intercept

Back in 1993-6 when I was working on Internet security and payments at CERN
and the Web Consortium the priority was to make payments on the Web, not
make it resistant to government intercept. The next priority was to
establish the authenticity of news Web sites. There were several reasons
for that set of priorities, one of which was that the technology we had
available was limited and it was impractical to do more than one public key
operation per session and it was only practical to use public key some of
the time. Severs of the day simply could not handle the load otherwise.

Twenty years later, much has changed and we can do much more. The designs
do not need to be constrained in the way they were then.

It is not a question of whether email is encrypted in transport OR at rest,
we need both. There are different security concerns at each layer.

3) We need more than one PKI for Web and email security.

PGP and S/MIME have different key distribution models. Rather than decide
which is 'better' we need to accept that we need both approaches and in
fact need more.

If I am trying to work out if an email was really sent by my bank then I
want a CA type security model because less than 0.1% of customers are ever
going to understand a PGP type web of trust for that particular purpose.
But its the bank sending the mail, not an individual at the bank.
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