[Cryptography] What is Apple's public signing key?

[Henry Baker]

Now that every govt in the world has Apple in its sights, how secure is the digital signature system that Apple uses to sign its firmware?

Which algorithm is used?

Which parameters are chosen?

Can these parameters have hidden back doors?

Are there any rainbow/NOBUS attacks?

Are there any methods similar to those used for passwords that can be used to slow down a brute force digital signature attack?