On Thu, Aug 08, 2002 at 09:15:33PM -0700, Seth David Schoen wrote:
Back in the Clipper days [...] "how do we know that this tamper-resistant chip produced by Mykotronix even implements the Clipper spec correctly?".
The picture is related but has some extra wrinkles with the TCPA/Palladium attestable donglization of CPUs. - It is always the case that targetted people can have hardware attacks perpetrated against them. (Keyboard sniffers placed during court authorised break-in as FBI has used in mob case of PGP using Mafiosa [1]). - In the clipper case people didn't need to worry much if the clipper chip had malicious deviations from spec, because Clipper had an openly stated explicit purpose to implement a government backdoor -- there's no need for NSA to backdoor the explicit backdoor. But in the TCPA/Palladium case however the hardware tampering risk you identify is as you say relevant: - It's difficult for the user to verify hardware. - Also: it wouldn't be that hard to manufacture plausibly deniable implementation "mistakes" that could equate to a backdoor -- eg the random number generators used to generate the TPM/SCP private device keys. However, beyond that there is an even softer target for would-be backdoorers: - the TCPA/Palladium's hardware manufacturers endoresment CA keys. these are the keys to the virtual kingdom formed -- the virtual kingdom by the closed space within which attested applications and software agents run. So specifically let's look at the questions arising: 1. What could a hostile entity(*) do with a copy of a selection of hardware manufacturer endorsement CA private keys? ( (*) where the hostile entity candidates would be for example be secret service agencies, law enforcement or "homeland security" agencies in western countries, RIAA/MPAA in pursuit of their quest to exercise their desire to jam and DoS peer-to-peer file sharing networks, the Chinese government, Taiwanese government (they may lots of equipment right) and so on). a. Who needs to worry -- who will be targetted? Who needs to worry about this depends on how overt third-party ownership of these keys is, and hence the pool of people who would likely be targetted. If it's very covert, it would only be used plausibly deniably and only for Nat Sec / Homeland Security purposes. It if becomse overt over time -- a publicly acknowledged, but supposedly court controlled affair like Clipper, or even more widely desired by a wide-range of entities for example: keys made available to RIAA / MPAA so they can do the hacking they have been pushing for -- well then we all need to worry. To analyse the answer to question 1, we first need to think about question 2: 2. What kinds of TCPA/Palladium integrity depending "trusted" applications are likely to be built? Given the powerful (though balance of control changing) new remotely attestable security features provided by TCPA/Palladium, all kinds of remote services become possible, for example (though all to the extent of hardware tamper-resistance and belief that your attacker doesn't have access to a hardware endorsement CA private key): - general Application Service Providers (ASPs) that you don't have to trust to read your data - less traceable peer-to-peer applications - DRM applications that make a general purpose computer secure against BORA (Break Once Run Anywhere), though of course not secure against ROCA (Rip Once Copy Everywhere) -- which will surely continue to happen with ripping shifting to hardware hackers. - general purpose unreadable sandboxes to run general purpose CPU-for-rent computing farms for hire, where the sender knows you can't read his code, you can't read his input data, or his output data, or tamper with the computation. - file-sharing while robustly hiding knowledge and traceability of content even to the node serving it -- previously research question, now easy coding problem with efficient - anonymous remailers where you have more assurance that a given node is not logging and analysing the traffic being mixed by it But of course all of these distributed applications, positive and negative (depending on your view point), are limited in their assurance of their non-cryptographically assured aspects: - to the tamper resistance of the device - to the extent of the users confidence that an entity hostile to them doesn't have the endorsement CA's private key for the respective remote servers implementing the network application they are relying on and a follow-on question to question 2: 3. Will any software companies still aim for cryptographic assurance? (cryptographic assurance means you don't need to trust someone not to reverse engineer the application -- ie you can't read the data because it is encrypted with a key derived from a password that is only stored in the users head). The extended platform allows you to build new classes of applications which aren't currently buildable to cryptographic levels of assurance. eg. It allows general purpose policies to be built just by writing policy code that sits in a Trusted Agent code compartment, without having to figure out how to do split-trust (a la mixmaster chaining), or forward-secrecy or secret-sharing or any of the other funky stuff; you can just implement some policy code and it becomes so. The danger is people will use it to build applications with squishy interiors, with no cryptographic assurance. Forward-secrecy implemented only by a policy in a Trusted Agent that sets a time-limit on access. Anonymity but only in the sense that you trust the hardware isn't tampered with, etc etc. It will be really tempting because: - it's much easier: network distributed crypto protocols are relatively complex - you can build things you can't otherwise build, the are currently unsolved problems with distributed crypto protocols - even where good crypto protocols exist, people will defend not using them by claims to paranoia: "What you think the NSA has tampered with your CPU?", or just laziness, cost of implementation etc So in short probably mostly the answer will be "No", people won't still aim for cryptographic assurance. And so a big networked world of distributed applications with a very squishy and insecure interior inside the closed world will be built. The new application spaces squishy interior -- like a corporate firewall with poor to no internal security -- could be ok if you could be sure the firewall is 100% guaranteed reliable. TCPA/Palladium proponents are effectively claiming it be an air-gap grade firewall guarding the distributed closed world application spaces squishy interior. But there is a problem: there are master keys by-passing all that -- the endorsement CA's private keys. 4. What coming political battles will result? a. If TCPA/Palladium systems get built -- and it may be politically unstoppable given the power of the distributed security paradigm it opens up -- then the battle of the coming decades will center around control of access to that squishy interior. The keys that control access to the closed world are the endoresment CA private keys. b. You will see many clipper like attempts by governments attempting to make policies surrounding conditional access to that closed world: - law enforcement access to the endorsement private CA keys controlling access, so they can setup sting operations, demand that ISPs and ASPs collaborate with virtualized versions of network services so they can trace things - NSA designed protocols to allow such things, black box mediated, court order approved, split database access to hardware manufacturers private keys c. As b. progresses RIAA/MPAA will chime in protesting that: - Kazaa2 is distributing 10 exabytes a day of ripped recent release content not based on BORA (which is now somewhat harder), but on ROCA (Rip Once Copy Anywhere) as the content rippers move into hardware hacking territory - the RIAA/MPAA can't hack, spoof or jam kazaa2 with bogus content because cypherpunks have fixed the protocols using WoT, certified content, and other crypto-fu so they can't even observe who's downloading what or who's serving what - and therefore they also demand access to the closed world so they can exert their recent legal rights to hack and DDoS the file sharing networks d. Unauthorised access to the closed environment (by hacking your own hardware) will become illegal with DMCA like restrictions (if it wouldn't already be where some relation to copyright could be drawn). e. Software companies, and OS vendors will follow Microsoft's current lead into an unholy battle with highlights such as: - undocumented APIs to gain advantage over competitors, not only hardware hacking required to discover APIs, but attestation to ensure only those companies who have licensed the right to use the API can use it - incompatible file formats to lock out competition with hardware tamper resistance levels of assurance, even file formats that must have certified documents for applications to open them, so even if you had the spec you couldn't be compatible - copyright protection with software encrypted for the CPU, so you can't even audit the static code - software renting models again enforced by hardware - whole collection of 2nd generation IP "innovations" which will be built on top of such things - charge per person you share file in a given document format; - charge per format conversion f. Lucky's Documentat Revocation lists to allow governments, companies etc to to some extent after the fact control distribution of data g. Increasingly minute enforcement of repressive levels of IP tracking, and arbitrarily user hostile, fair-use eroding document viewing and use policies 5. What could be done to protect the user? a. implement cryptographic assurance inside the closed space where possible -- that way if you are targetted by someone able to get inside it you still have the same protection as now. b. use web-of-trust techniques to provide an overlay of trust on the endorsement trust. ie users endorse their own machines to say "this is my machine" this implies that either: - it's not tampered with (presuming the user himself was not a target of some attack or investigation) - or the only tamperer is the certifying user web-of-trust overlaid on the hardware endorsement helps as: - This makes the endorsement keys less useful in a covertly obtained endorsement CA private key scenario - Even if there are court authorized law enforcement access to endorsement CA private keys, or RIAA/MPAA access to endorsement CA private keys you can to the extent of your connectivity in the web of trust, better avoid using the services of rogue agents inside the closed space. c. Demand ability to audit information in-flows into trusted agents where there are unauditable out-flows; demand that this is implemented in a way which allows code under user control to audit d. Demand the ability to audit information out-flows, where there are unauditable in-flows or sensitive user data processed by the application; similarly demand that this is implemented in a way which allows code under user control to audit e. Demand cryptographically assured anonymity protection so that there are no "trusted third parties" who can link your network usage and identify you. e. Other ideas? (Other than to lobby to prevent the building or use this model). Adam -- http://www.cypherspace.org/adam/ [1] "FBI Bugs Keyboard of PGP-Using Alleged Mafioso", 6 Dec 2000, slashdot http://slashdot.org/yro/00/12/06/0255234.shtml --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majordomo@wasabisystems.com