伪随机性是密钥序列的不可预测性的重要度量指标。通过选择适当的比特串并分析其个数的奇偶性,证明了广义自缩序列b(ak-1)和b(ak+1)的最小周期达到最大,即2^(n-1)。类似地,讨论若干类广义自缩序列的最小周期,如:b(ak-1+ak+2),b(ak-2+ak-1),b(ak-2+ak+2),…等,在大多数情形下证明了它们的最小周期达到最大,即2^(n-1)。
Stream ciphers use binary sequences with good pseudo randomness as key streams to enerypt messages. By analysing the appearing times of the bit string "101" in generalized self-shrinking sequences b (ak-l) and b (ak+l), it is proved that their least periods reach the maximum, namely 2^ (n-1). In the same way, we discuss the least periods of generalized self-shrinking sequences b (ak-l+ak+2),b (ak-2+ak-l),b (ak-2+ak+2), ...,etc, it is proved that in most cases their least periods reach the maximum.