The key exchange algorithms need connect with the CA institution because the communication sides need the public key each other, this confines the application of this algorithm.

• 而所介绍的密钥交换要求通信双方事先知道对方的公开密钥，这就必然要与证书发放机构相联系才能保证最大的安全，这样就限制了其应用范围。