hash | 易学教程

How to make “MessageDigest SHA-1 and Signature NONEwithRSA” equivalent to “Signature SHA1withRSA ”

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问题 I am interested in applying a SHA-1 hash with RSA signature to some data, but I need to do it in two steps - apply hash first and then sign the data. The Signature.sign() function appears to create a more complex (ASN.1?) data structure that is ultimately signed (see this question). How can I make the two equivalent without using any external libraries like BouncyCastle? Apply hash and sign in single step with Signature: PrivateKey privatekey = (PrivateKey) keyStore.getKey(alias, null); ...

HashMap

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HashMap也是我们使用非常多的Collection，它是基于哈希表的 Map 接口的实现，以key-value的形式存在。在HashMap中，key-value总是会当做一个整体来处理，系统会根据hash算法来来计算key-value的存储位置，我们总是可以通过key快速地存、取value。下面就来分析HashMap的存取。一、定义 HashMap实现了Map接口，继承AbstractMap。其中Map接口定义了键映射到值的规则，而AbstractMap类提供 Map 接口的骨干实现，以最大限度地减少实现此接口所需的工作，其实AbstractMap类已经实现了Map，这里标注Map LZ觉得应该是更加清晰吧！ public class HashMap<K,V> extends AbstractMap<K,V> implements Map<K,V>, Cloneable, Serializable 二、构造函数 HashMap提供了三个构造函数： HashMap()：构造一个具有默认初始容量 (16) 和默认加载因子 (0.75) 的空 HashMap。 HashMap(int initialCapacity)：构造一个带指定初始容量和默认加载因子 (0.75) 的空 HashMap。 HashMap(int initialCapacity, float loadFactor

Dictionary = Hash?

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问题 Is a dictionary basically just a hash table? Also bonus: In the Ruby code "Hash.new {0}" what is the "{0}" at the end for? 回答1: The words table, dictionary and map are often used synonymously (in the context of data structures). A hash table/hash map is one kind of table/dictionary/map. The {0} is a block (anonymous function) which ignores its argument and returns the number 0. The block given to Hash.new is called to produce a default value when a key is not found in the hash map. I.e. if I

Access Ruby hash variables

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问题 I am pretty new to ruby and sinatra but basically I have this route: put '/user_list/:user_id' do puts request.params["model"] end and it returns the following {"password":"36494092d7d5682666ac04f62d624141","username":"nicholas","user_id":106,"firstname":"Nicholas","email":"nicholas@macpractice.com","is_admin":0,"lastname":"Rose","privileges":""} I am now having a hard time accessing values of each of those. It doesn't really seem to be in hash format so I can't really do request.params[

Is it okay to store salts with hashes?

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问题 My understanding is that a salt is not intended to be secret, it is merely intended to be different from any centralized standard so that you can't develop a rainbow table or similar attack to break all hashes that use the algorithm, since the salt breaks the rainbow table. My understanding here might not be completely correct, so correct me if I'm wrong. In a widely-used piece of open-source software, the salt would be widely known, and this opens you up to attacks because now they can

Python implementation of Jenkins Hash?

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问题 Does there exist a native Python implementation of the Jenkins hash algorithm(s)? I need a hash algorithm that takes an arbitrary string and turns it into an 32-bit integer. For a given string, it must guarantee to return the same integer across platforms. I have looked at the ELF hash algorithm, of which I have found a Python implementation. Could this be a suitable replacement given the above criteria? (http://www.partow.net/programming/hashfunctions/#ELFHashFunction) 回答1: This native

Convert an array into an index hash in Ruby

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问题 I have an array, and I want to make a hash so I can quickly ask "is X in the array?". In perl, there is an easy (and fast) way to do this: my @array = qw( 1 2 3 ); my %hash; @hash{@array} = undef; This generates a hash that looks like: { 1 => undef, 2 => undef, 3 => undef, } The best I've come up with in Ruby is: array = [1, 2, 3] hash = Hash[array.map {|x| [x, nil]}] which gives: {1=>nil, 2=>nil, 3=>nil} Is there a better Ruby way? EDIT 1 No, Array.include? is not a good idea. Its slow . It

Hashing and password_verify

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问题 I'm working with my little PHP project and I'm trying to implement hashing on registration and I need to verify my hashed password when user want to log in. I tried a lot but I don't really get how I could use password_verify function in my code. In my registration.php I have a code: $username = $_POST['username']; $password = password_hash($_POST['password'], PASSWORD_DEFAULT); $email = $_POST['email']; My login.php file looks like this: $username = $_POST['username']; $password = $_POST[

Trying to understand password_verify PHP

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问题 I am trying to understand how password_verify work to use it for resetting the password. I would've thought this would've worked, but the hashed don't seem to match? $sUniqueCode = uniqid('1234', true); $sHash1 = password_hash($sUniqueCode, PASSWORD_DEFAULT); $sHash2 = password_hash($sUniqueCode, PASSWORD_DEFAULT); $sHash3 = password_hash($sUniqueCode, PASSWORD_DEFAULT); echo "Hash 1: ".$sHash1."<br>"; echo "Hash 2: ".$sHash2."<br>"; echo "Hash 3: ".$sHash3."<br>"; if(password_verify($sHash1,

Perl sorting hash by values in the hash

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问题 I think I have the right idea but there's some syntax/convention thing I'm messing up, because I get the error "Global symbol %timeHash requires explicit package name". Code: foreach $key (sort hashValueDescendingNum (keys(%timeHash))) { print "\t$key\t\t $timeHash{$key}\n"; } sub hashValueDescendingNum { my $hash = shift; $hash{$b} <=> $hash{$a}; } 回答1: Inline foreach my $key (sort { $timeHash{$b} <=> $timeHash{$a} } keys %timeHash) { print "\t$key\t\t $timeHash{$key}\n"; } Using a custom