How to distribute system parameters in identity-based encryption

Question

Identity-based encryption papers describe that system parameters are declared as public. However,in real scenario, how to distribute system parameters to users?

Answer 1

Public parameters (or system parameters as you call them) can be distributed however you want. Papers which introduce Identity-based Encryption schemes usually only present the scheme and not how it can be applied in the real world ¹. The public parameters in IBE can be compared to the pre-shared data in the Diffie-Hellman key exchange protocol where both parties have to agree on a shared modulus and generator before starting the protocol. There are different ways to distribute such data. Here are two:

• Bake (put into the application code) the public parameters into the application, so that every client has the same parameters and don't need additional trust negotiations. This will be a trust root.

• Query the public parameters from some other party in a secure manner (signed and not necessarily encrypted). Each client has to have some trust root (certificate of the third party) for this to work.

^{1 If you see a commercial product which uses IBE/HIBE/ABE/PE/HVE/FE, please write a comment.}