SEARCH KEYWORD -- TRUE RANDOM


  The Problem with Random Numbers

Today, let's talk about how to generate true random numbers. This is an extremely difficult problem, but it involves some very interesting content. First of all, the random numbers provided by programming languages are pseudo-random numbers.  The V8 engine’s official website has an article that particularly reminds everyone of this point. The built-in random numbers are not true random numbers but pseudo-random numbers. Math.random() returns a Number value with po...

   RANDOM NUMBER,TRUE RANDOM,PSEUDO RANDOM,HISTORY     2024-06-21 21:09:14

  One reason why mcrypt responds slowly

This morning one colleague came over and talked about one script which used mcrypt responded very slowly, the server configurations are fine. But the reason for the slowness is unknown. Here is one script which reproduces the issue: <?php $dmcryptText = "dummy"; $key = "foobar"; $size = mcrypt_get_iv_size(MCRYPT_BLOWFISH,MCRYPT_MODE_ECB); $iv = mcrypt_create_iv($size); //Take care $m = mcrypt_ecb(MCRYPT_BLOWFISH, $key, $dmcryptText, MCRYPT_DECRYPT, $iv); var_dump($m); When 20 requests of&...

   SOLUTION,SLOW,MCRYPT,RESPONSE,PHP     2012-09-27 12:03:16

  A trap about PHP random number

The method to get random number in PHP is very simple, we only need to use rand() function. int rand ( int $min , int $max ) One function call can return the random number in a specified range. But in fact, the random number in computer is actually pseudorandomness, generally to increase the randomness, we may set a random seed before calling rand(). void srand ([ int $seed ] ) According to other language features, we should pass a time value as a parameter to the srand() function, generally...

   PHP,rand,srand,mt_rand     2013-06-07 09:10:10

  Tips to improve JavaScript efficiency

Writing JavaScript code is tedious and error prone. You not only need to implement the necessary functions, but also need to ensure cross browser compatibility. This often causes the low efficiency of JavaScript developers. Here we recommend 12 tips you can benefit from. 1. Remove array element by index If we want to remove one element in an array, we can use splice. function removeByIndex(arr, index) { arr.splice(index, 1); } test = new Array(); test[0] = ’Apple’; test[1] = &rsq...

   JavaScript,Tips,Array     2013-07-27 20:50:40

  A serious security vulnerability found in MySQL/MariaDB

Recently a serious security vulnerability was found in MySQL/MariaDB. It relates to the access to the database. The issue is described below.When a user connects to MariaDB/MySQL, a token (SHA over a password and a random scramble string) is calculated and compared with the expected value. Because of incorrect casting, it might've happened that the token and the expected value were considered equal, even if the memcmp() returned a non-zero value. In this case MySQL/MariaDB would think that the p...

   MySQL,MariaDB,bug,fix,password,memcmp()     2012-06-11 10:28:09

  HeartBleed: Inside the heart, what causes the bleeding?

Just after a few weeks since Apple's famous goto fail bug, there is one bug in OpenSSL which catches the attention from the world again. The bug is named HeartBleed, found in OpenSSL library, a famous open source library supporting lots of  SSL/TLS communication among server/client applications. The reason why this bug catches the attentions from the world is it affects almost all sites which are using the affected OpenSSL library, these includes many applications like Nginx server, some v...

   OpenSSL,HeartBleed     2014-04-09 05:47:30

  Cool HTML5 matrix effect

Do you still remember the movie The Matrix? Do you still remember the cool matrix effect in that movie? How is that effect achieved? Shaun Dunne shared a piece of HTML5 code which displays a cool matrix effect. The matrix demo can be found here. Below is the code which he achieves this effect: with var s = window.screen; var width = q.width = s.width; var height = q.height = s.height; var letters = Array(256).join(1).split(''); var draw = function () { q.getContext('2d').fillStyle='rgba(0,0,...

   Matrix,HTML5     2013-08-14 08:03:34

  FTP active mode and passive mode

1. What's active mode and passive mode a. FTP has two ports to control: Port 20 is for data transfer Port 21 is for control or establish TCP connection b. The process of active connection Note: C represents Client and S represents Server S opens port 20 and 21 C connects to port 21 of S with a random port, this port can be between 1024 and 65536, it sends port+x to server at the same time to specify C(X)->S(21) When S receives the command, it will sends back ACK, S(21)->C(X) S will set ...

   FTP,Active mode,Passive mode     2013-04-01 07:01:25

  Some frequently used ES6 code snippets

Below are a list of ES6 code snippets which are used frequently. Hope that it will be helpful. 1. Shuffle array elements let arr = [67, true, false, '55'] arr = arr.sort(() => 0.5 - Math.random()) console.log(arr) // [ '55', 67, false, true ] 2. Remove characters which are not numbers const str = 'xieyezi 23213 is 95994 so hansome 223333' const numbers = str.replace(/\D/g, '') console.log(numbers) // 2321395994223333 3. Reverse sequence or words const sentence = 'xieyezi js so handsome, lol.'...

   JAVASCRIPT,ES6,CODE SNIPPET,TIPS     2022-04-10 07:56:07

  Shell script common interview questions

Shell script is frequently used when monitoring system status on Linux. It's not an easy task to write shell script but it's a very important skill for developers and system administrators to ease work and automate common tasks. This post will share some common interview questions about shell script. 1. Get random characters(8 characters) Method 1 # echo $RANDOM |md5sum |cut -c 1-8 471b94f2 Method 2 # openssl rand -base64 4 vg3BEg== Method 3 # cat /proc/sys/kernel/random/uuid |cut -c 1-8 ed...

   LINUX,INTERVIEW,SHELL SCRIPT     2018-09-28 10:46:00

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