Which statements are correct

Diffie$-$Hellman protocol is an example of the key transport scheme.

In asymmetric cryptosystems the communication parties' public keys should be authenticated to provide security against the man$-$in$-$the$-$middle attack, and certificates allow for that.

Cryptographic certificates do not require a trusted Certifying Authority.

Dirichlet's drawer principle or the pigeonhole principle relate to elliptic curve cryptography.