# Mumbo

# 题目：

Alice decides to use RSA with the public key N = 1889570071. In order to guard against transmission errors, Alice has Bob encrypt his message twice, once using the encryption exponent e1 = 1021763679 and once using the encryption exponent e2 = 519424709. Eve intercepts the two encrypted messages

# DES 与 Feistel Cipher Structure 的不同点

DES是在 Feistel Cipher Structure (FCS) 基础上构建的加密算法。在加密过程中， DES在FCS开始前添加 Initial Permutation 和对原来 FCS 的输出添加了 逆向的 Initial Permutation。 同时，也通过circular shift 和 permute 实现了 SubKey 的生成。

For some reasons, I find myself have difficulty with learning from class lessons. It’s not like you have a quick forward or play back button in a class. Following a teacher’s voice sometime might be hard while other time might be dull. So, most of the time I would choose to study my subjects by reading books. In the end, I basically learn most of the stuff by myself. This isn’t an easy task either, but I have the luck to come across many great books that act as a careful teacher for me.