## Detailed explanation of DES encryption and decryption - Java,Python

DES introduction
Des (Data Encryption Standard) is by far the most widely used and popular block cipher algorithm in the world. Its packet length is 64 bits and the key length is 56 bits. It was developed by IBM in the United States. It is an early development and modification of Lucifer cipher. Every five years, the National Security Agency ( ...

Posted on *Wed, 01 Dec 2021 09:34:48 -0500* by **kykin**

## Final review of fundamentals of information security Mathematics (cryptography)

Final review of fundamentals of information security Mathematics:
Chapter 1:
1. Find all prime numbers within 100
100
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
2. Solve GCD (45100)
gcd(45,100)=5
100=45*2+10
45=10*4+5
10=5*2+0
3. Find the maximum common divisor of 963657 and express it as the linear combinati ...

Posted on *Wed, 17 Nov 2021 23:17:48 -0500* by **eightFX**

## Python hash function and message authentication experiment

preface
Tip: the test run environment is Python 3.7.5 and the IDE is Pycharm2020.1. The article contains three questions: 1. Calculating hash value and message authentication; 2. Avalanche effect of hash function; 3. Brute force MD5. Copying the past source code may need to change the output format.
1, Calculate hash value and message a ...

Posted on *Fri, 29 Oct 2021 04:11:29 -0400* by **alsouno**

## Reverse learning encryption algorithm

Reverse learning (I) encryption algorithm
preface
As a school course, I don't understand. ctf has no teammates and can only sign in pwn hands. Today, I'm ready to open a new pit!
(you pwn are still a vegetable chicken. Why are you opening a new pit)
The following contents are mainly organized according to wiki.
Topic
Base64
base64 must b ...

Posted on *Sun, 24 Oct 2021 06:18:31 -0400* by **woza_uk**

## [cryptography] understand the Padding mode

Cryptography - Padding mode
When encrypting data, some encryption algorithms need plaintext to meet certain length requirements, such as DES and AES. For grouping encryption, plaintext is a multiple of packets, but in most cases, the probability of plaintext meeting the requirements is very low. In previous implementations, my implementation ...

Posted on *Sun, 10 Oct 2021 07:33:13 -0400* by **new_programmer**

## CTF crypto 2021-10-4 record

Basic knowledge
CBC flip attack
Introduction:
When one of our values C is obtained by the exclusive or of A and B C = A XOR B that A XOR B XOR C is obviously = 0 When we know B and C, it's easy to get the value of A A = B XOR C Therefore, A XOR B XOR C is equal to 0. With this formula, we can set our own value at the end of XOR operat ...

Posted on *Mon, 04 Oct 2021 16:36:34 -0400* by **gitosh**

## crypto experiment report

Cryptography experiment report
The author participated in an experimental report assignment of network attack and defense innovation practice course in freshman and primary school, which is a pure entry level
Experimental objectives
Part I
The following ciphertext is encrypted with classical password. Please identify and write the ...

Posted on *Thu, 02 Sep 2021 17:25:55 -0400* by **Shawazi**