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To resolve the problem that the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems is too high, an improved selected mapping (SLM) is proposed in this paper. By scaling the selected signal amplitude and dividing the OFDM vector in the transmitter, it saves the system bandwidth and reduce the PAPR efficiently, and it doesn’t need side information to be sent. At the same time, the random phase sequence information is rapidly recovered by using related detective algorithm, which largely raises the detective efficiency in the receiver. The simulation results show that the improved SLM could reduce the PAPR more efficiently while the bit error rate (BER) is similar to the one of the typical SLM.

Expression of blind message in the optimal-type blind signature scheme was modified so that it can combine with threshold signature, which leads to an effective threshold blind signature scheme based on elliptic curve cryptography, it has the following securities: strong verifiability, nonrepudiation, unforgeability, blindness and robustness, and also takes advantage of characteristics of elliptic curve such as higher security and shorter key, as well as lower computational complexity compared with the previous schemes.