Using certificates also opens up for the possibility of removing the key transfer between Alice and Bob completely! This is an important feature when secure communication is being implemented between a large number of participants. This is because none of Bob’s ability to trust the public key he receives now depends on whether he is actually communicating with Alice or not. His ability to trust the key depends solely upon his trust relationship with the trusted third party. This means that Bob might actually be talking to a database that stores certificates for many users, much like a phone book. Bob can use his trusted third party’s.
