Yongjian Hu

## Pages

Currently I am learning some knowledge of cryptography. In this blog, I made some notes about it and I will keep updating these notes. Abstract Algebra Basic Group Theory Group Theory is the fundamental tool for studying symmetry and the foundation of cryptography. Here, Definition and examples DEFINITION 1.1 A group is a set $G$ together with a binary operation $(a,b) \mapsto a * b:G \times G \rightarrow G$ satisfying the following conditions: G1: (associativity) for all $a,b,c \in G$, $$(a * b) * c = a * (b * c)$$ G2: (existence of a neutral element) there exists an element $e \in G$ such that $$a * e = a = e * a$$ G3: (existence of inverses) for each $a \in G$, there exists an $a' \in G$ such that $$a * a' = e= a' * a$$ .
2019-07-28
2分钟阅读时长

2018-09-01
7分钟阅读时长