1. Governmental Control of Network Activities CS 239 Advanced Topics in Computer Security Peter Reiher September 30, 2010

2. The Issue
Governments worldwide want to wiretap electronic communications
Not just POTS telephone calls
But all modern cyber communications
Skype and other VoIP
Blackberry and other
Twitter, etc.

3. Why? For criminal investigations For national security issues
Probably, in some cases, to spy on their citizens
Communications is moving away from traditional telephony
So government wiretapping follows

4. Aspects of the Problem Societal and international Technical
We’re primarily concerned with the technical issues
In particular, can government get what it wants?
If so, at what price?

5. Why Is This Problematic?
The telephone model of communications was different
Dumb terminals, smart network
The Internet reverses that
Smart terminals, dumb network
Telephony wiretapping techniques aren’t always feasible for the Internet

6. Wiretapping Telephones
The result:
If Ma helps, easy to tap any telephone call
Important properties:
Circuit switched
All elements under central control
Telephones not intelligent
Ma Bell’s Cloud
Analog signals

7. Wiretapping the Internet
The result:
There’s no Ma to help
Important properties:
Maybe there’s nobody to help
Packet switched
No central control or ownership
Very smart endpoints
Digital signals
The Internet Cloud

8. The Detailed Problems Packet switching Intelligence at the endpoints
No central control
Digital signals
Not necessarily a big deal

9. Packet Switching
You can’t get a whole transmission just anywhere on its path
Need to tap in particular places
Also, need to reassemble the transmission
Maybe not that big a deal, though

10. Smart Endpoints Endpoint can do what it wants Encrypt the traffic
Using its own keys
Exert some control on routing
Use overlay and peer techniques
Perhaps even mix networks
The folks in the middle can’t stop them
Perhaps can’t even tell they’re doing it

11. No Central Control Multiple parties involved Machine’s owners
ISPs they connect to
Multiple core ASes
Law enforcement must work with many parties to wiretapp

12. Modern Applications How does something like Skype protect traffic?
Peer routing techniques
With no central control
End-to-end cryptography
Keys generated only at endpoints
Little or no recordkeeping

13. What Do Governments Want?
To listen in on any conversation
Even if encrypted
On a moment’s notice
Or at least pretty quickly
Without the parties noticing
Cheaply and reliably

14. The Cryptography Issue
The transmissions are encrypted
With high-quality crypto
Like AES
The keys are generated by the parties at the endpoints
They don’t share the keys with anyone
How can the government listen in?

15. Options Force no crypto Nobody would accept that Force crappy crypto
Also unacceptable
Force providers to know the keys
Use Skipjack-esque key escrow

16. Forcing Providers to Keep Keys
Folks like the Skype and Research In Motion
When communications occur, their products create the keys
Sharing them with a company server
Government gets the keys from server when it wants

17. Skipjack Approaches
Build in methods of deriving the key from the data transmission
Using special types of crypto
Companies don’t keep the keys
Government doesn’t need to go to them to get the keys