My first question is how to verify signature using only r,s and elliptic curve parameter? Next question is that, why ethereum (also bitcoin I think) uses hashed public key as an address instead of directly use public key as an address?

My first question is how to verify signature using only r,s and elliptic curve paramete, and an address (which is hashed of public key, so cannot retrieve public key from the address)?

Next question is that, why ethereum (also bitcoin I think) uses hashed public key as an address instead of directly use public key as an address?