Standard for public-key certificate formats x509 specifies

Question

In addition to providing a standard for public-key certificate formats. X.509 specifies an authentication protocol. The original version of X.509 contains a security flaw. The essence of the protocol is

A → B: A(tA, rA, IDB)

B → A: B{t_B, r_B, ID_A, r_A }

A → B: A{r_B}