A method for security in a passive optical network is disclosed. The method includes, at an optical line termination (OLT): detecting an optical termination device and establishing a connection with the device; generating a first authentication message including a first random number; and transmitting the first authentication message through the established connection. At the optical termination device, the method may include: receiving the first authentication message; calculating a first authentication code by using the first random number and a secret code stored at the device; and generating and transmitting to the OLT a second authentication message including the first authentication code. The method may further include, at the OLT: receiving the second authentication message; calculating a second authentication code by using the first random number and a secret code stored at the OLT; and authenticating the optical termination device if the first authentication code matches the second authentication code.