Abstract: To find a large number of orthogonal matrices is important for information security algorithms based on OFDM（Orthogonal Frequency Division Multiplexing）. The orthogonal matrix is used to reduce PAPR（Peak-to-Average Power Ratio） of the OFDM signal and is used as a key to encrypt the data. It is proved that the method to generate multiphase orthogonal matrix can be used to transform a single orthogonal matrix to those of much larger than [N!×NN], so any of those matrices can be used as a key to encrypt the data. Computer simulations show that the orthogonal matrices after transformation are similar to the original one in the performance of reducing PAPR of OFDM signal, so they can be used for information security algorithm based on OFDM.

Key words: Orthogonal Frequency Division Multiplexing（OFDM）, Peak-to-Average Power Ratio（PAPR）, orthogonal matrix, information security, key

摘要： 寻找大量的正交矩阵，一方面用来降低OFDM（正交频分复用）信号的峰均功率比，一方面作为密钥使用，是基于OFDM的信息安全算法的重点。经证明用生成多相正交矩阵的方法，可将单一的用来降低OFDM信号峰均功率比的正交矩阵，变换为数量远大于[N!×NN]个的正交矩阵，具有了作为密钥的功能。计算机仿真表明，变换后的正交矩阵与原矩阵在降低OFDM信号峰均功率比的性能上类似，可用于信息安全算法中。

关键词: 正交频分复用, 峰均功率比, 正交矩阵, 信息安全, 密钥