Performance of OFDM Communication System with RSA Algorithm as Synchronization on SR Security Scheme Using USRP Devices

This paper presents simple physical layer security for protecting data transmission on confidential OFDM scheme. The principal idea is to utilize subcarrier on OFDM technology, the location of subcarrier will be randomized so the name of this security scheme is the SR (subcarrier randomization) security scheme. OFDM communication system is implemented real time with LabVIEW software on USRP devices. Randomization of the subcarrier location and its location return requires synchronization between the transmitter and receiver. RSA algorithm is asymmetric cryptography commonly used to encode transmitted data, but in this paper RSA algorithm is used as synchronization. In transmitter, plaintext is generated and the plaintext will be encrypted using RSA. The location change of bits of plaintext and ciphertext represents the location of the subcarrier to be random-ized. Whereas in the receiver, the ciphertext is decrypted using a private key on the RSA algorithm. With the synchronization technique the RSA algorithm on distance 1 meter can reduce bit errors from 19.04% to 0% in 32-QAM modulation and reduce bit errors from 28.57% to 4.76% in 64-QAM modulation. The output of decryption should be the same as the generated plaintext, so that the bit location changes of the ciphertext and the output of decryption represent the return of the subcarrier to its original position. The output of this paper proves that the system uses security does not degrade performance of system, even OFDM system can improve performance for their synchronization RSA algorithm.