I don't really even understand how the signing works, so I don't really get what would have to be done to sign an app on calc. Why would anything ever need to use 512 bit numbers except for high decimal precision?

You can't sign on-calc. Software like RabbitSign are used to sign an app after it's assembled on a computer. Signing an app basically makes it "valid" to the calculator, which checks the 512-bit signature to see if it's valid or not. If it's not valid, the app gets deleted after a certain number of runs (like a "trial" app).

Ducksign lets you send applications from one calc to another (unsigned apps will refuse to do so), but the expiration count will still exist unless Axe changes or unless you sign in on the computer.

That was me.  And, no, it doesn't take 10 minutes, it takes less than one minute for normal-sized apps.

See http://ourl.ca/7447/149857

Ducksign lets you send applications from one calc to another (unsigned apps will refuse to do so), but the expiration count will still exist unless Axe changes or unless you sign in on the computer.

That's also not entirely correct.  DuckSign signs the application; once it's signed, it's perfectly valid, just as if you signed it using RabbitSign or Wappsign or whatever.

The expiration count is not part of the application; it's something that's set by the OS as part of the normal installation process (I don't remember whether it's set at the beginning or end of the transfer, but anyway...)  And it doesn't have anything directly to do with app signatures.  If you write an application directly into Flash - regardless of whether or not it's signed - without also setting the expiration count, the app will expire after 16 runs.

As far as Axe goes, I believe Quigibo has said that he doesn't want to do this in Axe because of the risk of corrupting the calculator certificate.