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彩虹表

由 匆匆过客 提交于 2019-12-29 23:42:09
彩虹表（Rainbow Table）是一种破解哈希算法的技术，是一款跨平台密码破解器，主要可以破解MD5、HASH等多种密码。它的性能非常让人震惊，在一台普通PC上辅以NVidia CUDA技术，对于NTLM算法可以达到最高每秒103,820,000,000次明文尝试（超过一千亿次），对于广泛使用的MD5也接近一千亿次。更神奇的是，彩虹表技术并非针对某种哈希算法的漏洞进行攻击，而是类似暴力破解，对于任何哈希算法都有效。 一、彩虹表原理 这几乎是令人难以置信的，Roger迫不及待的去看了 http://www.project-rainbowcrack.com 所介绍的原理。这其实已经不是新的技术了，但是很遗憾的是，搜索“彩虹表原理”出来的文章对彩虹表原理的介绍都有不太正确，Roger就在这里简单的介绍一下，主要参考的是Wiki上的这篇 http://en.wikipedia.org/wiki/Rainbow_tables ，英文好的可以去看这篇论文 http://lasecwww.epfl.ch/pub/lasec/doc/Oech03.pdf 。 我们先来做点科普，哈希（Hash）算法就是单向散列算法，它把某个较大的集合P映射到另一个较小的集合Q中，假如这个算法叫H，那么就有Q = H（P）。对于P中任何一个值p都有唯一确定的q与之对应，但是一个q可以对应多个p

How can I get the same HMAC256-results in C# like in the PHP unit tests?

由 Deadly 提交于 2019-12-29 20:30:10
问题 I thought I would try and get the new Signed Request logic added to my facebook canvas application, to make this "easy" on myself I went to the facebook PHP sdk over at GitHub and took a look at the unit tests. My actual problem is that I cannot get the hash included in the request to match the hash I calculate using the application secret, and the data sent within the request. How this is meant to work is described at Facebook's authentication page. private string VALID_SIGNED_REQUEST =

PHP salt and hash SHA256 for login password

由 自古美人都是妖i 提交于 2019-12-29 13:00:13
问题 I've made encrypting of the password in my register script and they are stored in the database, and I have to use them to login, so I would want to use the unencrypted ones to login. I've read some of the threads in here but nothing is helping me. How can I add it in my login.php? The salt is also stored in the database. This is my register.php script for encrypting $hash = hash('sha256', $password1); function createSalt() { $text = md5(uniqid(rand(), TRUE)); return substr($text, 0, 3); }

Why do we use linear probing in Hash tables when there is separate chaining linked with lists?

由 六眼飞鱼酱① 提交于 2019-12-29 11:36:08
问题 I recently learned about different methods to deal with collisions in hash tables. And saw that the separate chaining with linked lists is always more time efficient, and for space efficiency we allocate a predefined memory for Linear probing which later on we might not use,for separate chaining we utilize memory dynamically, so is separate chaining with linked list not more efficient than Linear probing?if yes why do we then use Linear probing at all? 回答1: I'm surprised that you saw chained

Why do we use linear probing in Hash tables when there is separate chaining linked with lists?

由 穿精又带淫゛_ 提交于 2019-12-29 11:35:41
问题 I recently learned about different methods to deal with collisions in hash tables. And saw that the separate chaining with linked lists is always more time efficient, and for space efficiency we allocate a predefined memory for Linear probing which later on we might not use,for separate chaining we utilize memory dynamically, so is separate chaining with linked list not more efficient than Linear probing?if yes why do we then use Linear probing at all? 回答1: I'm surprised that you saw chained

How to generate short uid like “aX4j9Z” (in JS)

由 被刻印的时光 ゝ 提交于 2019-12-29 10:52:47
问题 For my web application (in JavaScript) I want to generate short guids (for different objects - that are actually different types - strings and arrays of strings) I want something like "aX4j9Z" for my uids (guids). So these uids should be lightweight enough for web transfer and js string processing and quite unique for not a huge structure (not more than 10k elements). By saying "quite unique" I mean that after the generation of the uid I could check whether this uid does already exist in the

Using pickle.dumps to hash mutable objects

由 走远了吗. 提交于 2019-12-29 09:32:23
问题 I understand why putting mutable objects in a dictionary is dangerous. However, converting all lists/sets to tuples/frozensets is expensive; and for many types, there's no easily available immutable versions at all. So, sometimes it may be worth hashing mutable objects directly, with the appropriate precautions to ensure the objects in question are never modified. Before I start implementing the very complicated custom hash functions for mutable objects, I wanted to check if there's any

how to hash the password and get it back

由 好久不见. 提交于 2019-12-29 09:23:27
问题 hey guys, i want to hash the password so it is totally encrypted, i am able to hash the password, but now the issue is i am not able to again get back the real password, is there any way i can get the real password using any of the hash, or is there any other way to encrypt and also decrypt the text into its original content... Please reply as soon as possible.. Thanks and regards abbas electricwala. 回答1: The whole point of hashing a password is so that you do not have to save passwords in

Which is the best password hashing algorithm for PHP? [duplicate]

由 冷暖自知 提交于 2019-12-29 09:06:45
问题 This question already has answers here : Secure hash and salt for PHP passwords (14 answers) Closed 6 years ago . I was just reading a post to create a login system and while reading I saw about password hashing. We are going to store an sha256 hash which is a string always containing 64 characters. This article is teaching to use sha256 hash function. After reading this, I did not stop and started to search more about creating secure login system and then I came up with this article by

What hashing function does Spark use for HashingTF and how do I duplicate it?

由 ╄→尐↘猪︶ㄣ 提交于 2019-12-29 08:46:16
问题 Spark MLLIb has a HashingTF() function that computes document term frequencies based on a hashed value of each of the terms. 1) what function does it use to do the hashing? 2) How can I achieve the same hashed value from Python? 3) If I want to compute the hashed output for a given single input, without computing the term frequency, how can I do this? 回答1: If you're in doubt is it usually good to check the source. The bucket for a given term is determined as follows: def indexOf(self, term):
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