Which two qualities of PKI key exchange overcome asymmetric cryptography scalability issues? (Choose two.)

A.
the trusted introducer uses the signed certificates of the endpoints that need to communicate

B.
PKI uses only a single trusted introducer

C.
the trusted introducer uses the private key of each enrolling user and the public key of the introducer as the signed certificate

D.
only the public key of the introducer has to be initially known and verified by all other entities

E.
the introducer digitally signs the public key of the user with the public key of the introducer to generate a signed certificate