Re: Is Your Identity Safe?

Dan Lanciani wrote:

>> I think you've missed the point. In spite of what the banks may tell >> you, there is no reason for the information required by an entity to >> verify your identity to also be sufficient for that entity to >> impersonate you. The attitude of, 'we need to know all about you so >> we can be sure who you are' (and consumers' acceptance of that >> attitude) is exactly the problem. > Then how can it be complete to verify your identity?

The currently fashionable approach would be for the credit agency (or equivalent) to hold the consumer's public key and deliver it to the bank or other entity desiring to verify the consumer's identity. The consumer could then sign the credit application (or whatever) with her secret key, proving her identity. (There are details, of course, and the application should probably be encrypted with the bank's well-known public key.) An advantage of using public key crypto is that even the credit agency doesn't have enough information to impersonate the consumer.

If you don't like public key crypto and you don't mind that the credit agency (but not the bank) has enough information to impersonate the consumer then take a look at Kerberos's model. It can provide mutual authentication of two parties without giving either enough information to impersonate the other, all using traditional symmetric crypto.

One nice thing about both approaches is that they could be phased in in such a way that they were completely optional both for consumers and banks. Let consumers register their public keys with the credit agencies who could then deliver them along with all the other personal data. Let banks use them for verification if they so choose. (Maybe provide a little incentive by saying that if a consumer registers a key and the bank decides not to use it and there is fraud the bank is strongly presumed to be at fault.)

Another feature is that unlike biometric and SecureID schemes, these approaches do not require the deployment of esoteric hardware. More importantly, since the required computing equipment on the consumer's end is working only for the consumer (i.e., it is not attempting to conceal something from its owner) it can be implemented as software on general purpose machines, e.g., desktops and PDAs. Chances are that the majority of consumers interested in registering their keys already have the required hardware. (This is not to say that the banks couldn't develop a nice easy-to-use crypto appliance for those who don't want to use general-purpose machines.)

To extend the approach to frequent transactions it would be a good idea to add an IrDa port to ATMs so they could talk to PDAs directly. (You don't want the consumer to have to copy long strings of digits by hand.) Again this does not require the bank to issue special "secure" hardware to the consumer because the PDA works for its owner, not for the bank.

The information that verifies that you are who you are is exactly the > same information that verifies that someone else is who you are.

That's true, and it is why there is ultimately no solution for the simple duress problem. The best we can do with something known is prove that that something is indeed known. However, we can contrive to do this in such a way that the something known is not disclosed in the process. And the entity to whom we are making the proof does not itself need to know the something at any time. That solves the phishing problem and the unintentional-disclosure-by-central-agency problem.

Dan Lanciani ddl@danlan.*com

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Dan Lanciani
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