密码学基础问题两道

[tesorouo]

1. The numbers 7 and 23 are relatively prime and therefore there must exist integers a and b such that 7a+23b=1. Find such a pair of integers (a,b) with the smallest possible a>0. Given this pair, can you determine the inverse of 7 in Z23?
Enter below comma separated values for a, b, and for inverse of 7 in Z23.
这题答案为什么不是10,-10,10?

2. What is the discete log of 5 base 2 in Z13? (i.e. what is Dlog2(5))
Recall that the powers of 2 in Z13 are <2>={1,2,4,8,3,6,12,11,9,5,10,7}
这题答案应该怎么算啊？老弄不懂Dlog到底应该怎么计算，求过程

[wynnsyt]

1. b = -3
2. 2^9≡5 所以答案是9