Digital Signature Wish List

Never having to type passwords in web pages.

Lots of unimportant web sites demand name and password for me to access them. I simply use the same password for them all, to reduce the administrative burden. This carries the risk that the owner of site a.com, knowing the name and password I use there, may try the same name/password combination at site b.com.

As long as all these sites are unimportant, that risk may be acceptable.

The real danger is that I, on a bad day, will type one of my serious passwords on a web page, and that this site records the password, and uses it to log on to a critical system, maybe my bank account.

So I need a web client certificate. Whenever a site—an important one or not—demands that I log in, I should be able to say: 1896 2A24 F677 3A55 6E4D BD46 D913 F313 8F5A 2AAB is the fingerprint of my key pair, please accept signatures by that key as proof of my identity, and stop nagging me about passwords.

Usually I'd want to use the same identity (my real ID) for all sites. The key pair will be protected with a passphrase, but the passphrase is not transferred from the web client, so accessing all sites using the same passphrase is not dangerous.

In some cases, maybe when accessing sites like anus.com, I might prefer not to reveal my real identity. I can safely protect several key pairs using the same passphrase, so password administration is not a problem. But some care must be taken, so the right id is presented to each site.

Never revealing reusable passwords to untrusted keyboards

Punching my PIN at ATMs is dangerous, I do (have to) trust my bank, but I really can't trust that the keyboard is not under surveillance. Internet cafés are even worse.

Even 1-time passwords may be stolen from keyboards, if the session hi-jacker is able to abort my logon attempt.

My mobile phone seems a reasonable password keyboard: I often carry it, and I use the keyboard for other purposes too, so you can't easily find my password by reading the fingerprints. But the passord should never leave the phone: it should only be used to unlock the key pair for a limited time, to decrypt incoming messages or sign logon requests and encrypt other outbound messages. Software updates to the phone must be severely restricted.

One web banking solution is based on 1-time passwords being SMS'ed to my phone. But my phone is now unlocked, anyone can steal it, and be able to receive my password SMS. Maybe I could configure it to require PIN for each incoming call or message, but that's too cumbersome. I need to receive encrypted SMS, or WAP Service Indications pointing to encrypted WAP pages, with encryption subject to a stricter PIN regime than normal phone and SMS.

WAP's Wireless Identity Module (WIM) seems a reasonable technology to do PKI in the phone, but I find little support for it. Some Nokia phones support WIM, but no SIM cards do, as far as I can see. The closest I can find, is Setec PKI eSIM™.

Group signatures

Institutions need group signatures, i.e. keys that can be used to sign, only if a certain combination of people has unlocked the key pair. E.g. at least two managers, where at leasst one of them is a senior manager. PGP seems to be able to implement these kinds of signatures.

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A more philosphical twist on digital identity.

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