Basic symbols
Let?
?denotes all the integers model?
, which can also be written as?![[n]](https://math.jianshu.com/math?formula=%5Bn%5D)
, for example:
![Z_{2}=[-2,-1,0,1,2]](https://math.jianshu.com/math?formula=Z_%7B2%7D%3D%5B-2%2C-1%2C0%2C1%2C2%5D)
,?![Z_{5}=[-5,-4,-3,-2,-1,0,1,2,3,4,5]](https://math.jianshu.com/math?formula=Z_%7B5%7D%3D%5B-5%2C-4%2C-3%2C-2%2C-1%2C0%2C1%2C2%2C3%2C4%2C5%5D)
while in the cryptography world, we hope each element in an integer set should have a inverse.
Unfortunately, not every?
?satisfy, so we introduce a new notion?
.
Let??denotes all the subset in?, let?
, then?
should have a inverse integer?
which also belongs to?, we list the elements of?
, and for each?
, we also have?.
