Architectural issues for network-layer identifiers

Stefan Savage

Dept of Computer Science & EngineeringUC San Diego

Historical context

IIn the beginning... it was amazing the net worked at all.

Everyone was a good actor.

Existing Internet design Focused on universal connectivity

IP address Identifiers purely for the purpose of connectivity Dst address for routing, Src to identify destination for replies Strictly voluntary

Actively trying to introduce homogeneous substrate Unbound usage model

Security not a significant consideration in the network layer; trust everyone equally

Cryptography expensive relative to transport Cryptographic abstractions limited

True when IPSec designed also

What has changed?

Many users/providers don’t want homogeneity Most src addresses today are NATed We want to limit who can talk to whom

Huge growth in criminal activity 10s of millions of compromised machines Sophisticated abuse of network layer

Problems

Network architecture provides “how” Security questions are mainly about “who” and

“what” Ad hoc, brittle mappings between two

Firewalls (address, port) Ingress/egress filtering DDoS filtering (ttl hack, blackholing, etc) Key issue

Can’t count on src address being correct or global Even if it is correct only represents existence of endpoint

Worth rethinking…

How might we design packet identifiers to provide useful attribution?

Attribution – working definition:The act of linking identity with action

Uses Authentication: who wants to do that?

Access control

Situational awareness: who is doing that now? Operational response (e.g. filtering DDoS, BotNet C&C)

Forensics: who did that in the past? Investigatory, evidentiary

Design options Meaning of identifier

Network attribute IP address: topological endpoint Path: topological route (StackPI)

Physical attribute Location: place packet sent from (used today in payment sys) Originator: machine packet sent from

User attribute Capability: right to access something Principal: evidence of individual

Scope of identifier (local, global, in-between) Who can interpret (anyone, trusted party, hybrid)

New opportunity

Crypto has advanced significantly Many operations are comparatively cheap now

10’s of microseconds Line-rate hardware implementations feasible

Completely new kinds of cryptography Groups, aggregates, append-only, IBE, Attribute-

based crypto, homomorphic crypto, broadcast systems, etc

Its not just encrypt, hash and sign anymore… New tools provide new design opportunities

Remaining agenda

Revisiting the Cryptographic toolbox (Boneh)

Local identifiers for access control (Casado)

Global identifiers for forensics (Savage)

Attribution To whom