Yeh et al. Protocol. In 2010, Yeh et al. [39] proposed a process oriented UMAP. The feature that differentiates this protocol from its predecessors is the DoS avoidance mechanism. In this protocol, the pairs of latest dynamic variables are stored at the reader side instead of the tag. The reader also maintains a flag to identify whether the tag/reader pair is fully synchronized or not.The nontriangular function used in the protocol is the rotation function (𝑅𝑜𝑡(𝑎, 𝑏)). The memory architecture of the UMAP is given in Table 5. The working principle of the Yeh et al. protocol is as follows: the protocol is the rotation function (𝑅𝑜𝑡(𝑎, 𝑏)). The memory architecture of the UMAP is as follows:
(1) The reader initiates the communication by sending a “Hello” message to the tag.
(2) As a response, the tag transmits the 𝐼𝐷𝑆 stored in its dynamic memory.
(3) After successful tag identification through the database, the reader generates two pseudorandom numbers 𝑛1 and 𝑛2. If the 𝐼𝐷𝑆 = 𝐼𝐷𝑆𝑛𝑒𝑤, the reader sets an internal flag 𝑓 = 0; otherwise the flag’s value sets to 1, the key 𝐾 updates and becomes equal to the tag’s 𝐼𝐷. After key updation, the reader calculates and sends message 𝑋 = 𝐴 ‖ 𝐵 ‖ 𝐶 ‖ 𝑓 to the tag.
𝐴 = (𝐼𝐷𝑆 ⊕𝐾 ) ⊕ 𝑛1
𝐵 = (𝐼𝐷𝑆 ∨ 𝐾) ⊕ 𝑛2
𝐾∗ = 𝑅𝑜𝑡 (𝐾 ⊕𝑛2, 𝑛1)
𝐶 = (𝐾∗ ⊕ 𝑛1) + 𝑛2
𝑓 = 𝑓𝑙𝑎𝑔 𝑏𝑖𝑡
𝑓 = 0 𝑖𝑓 𝐼𝐷𝑆 = 𝐼𝐷𝑆𝑁𝐸𝑊
𝑓 = 1 𝑖𝑓 𝐼𝐷𝑆 = 𝐼𝐷𝑆𝑂𝐿𝐷
(4) Upon receiving the challenge message, the tag updates the value of the key 𝐾 based on the flag status. After that 𝑛1 and 𝑛2 are extracted and the reader is authenticated.
(5) The successful reader verification leads to the calculation and transmission of the tag authentication challenge message 𝐷.
𝐾̈* = 𝑅𝑜𝑡 (𝐾 ⊕𝑛1, 𝑛2)
𝐷 = (𝐾̈ ∗ ⊕ 𝑛2) + 𝑛1
(6) In case of successful mutual authentication, the dynamic memory on both sides is updated.
𝐼𝐷𝑆𝑁𝑒𝑤 = (𝐼𝐷𝑆 + (𝐼𝐷 ⊕ 𝐾̈ ∗)) ⊕𝑛1⊕ 𝑛2
𝐾𝑁𝑒𝑤 = 𝐾∗