Abstract: Aiming at security flaws of interaction data between tags and readers in RFID system based on wireless channels, an ultra-lightweight two-way authentication protocol is proposed to ensure data security. An innovative encryption algorithm, left and right cyclic mobile composition operation, is defined. The algorithm fully combines Hamming weight carried by encrypted data, and moves left or right in different ways according to weight size relation, and moving digits are only related to weight. Without parameters, attackers have higher cracking difficulty while total calculation is reduced. Multi-angle analysis shows that the protocol has high security requirements and meets low-cost system calculation requirements.