你已经得到了一些很好的答案，但我猜你可以这样看: 加密: 如果你有正确的密钥，加密必须是可以解密的。

例子: 就像你发电子邮件一样。 您可能不希望世界上每个人都知道您正在给接收电子邮件的人写什么，但接收电子邮件的人可能希望能够阅读它。

散列: 哈希的工作原理类似于加密，但它不应该能够反转它。

例子: 就像你把钥匙插进一扇锁着的门里(就是那种你关门时就会锁上的门)。你不需要关心锁的具体工作原理，只要在你使用钥匙时它能自己解锁就行了。如果出现问题，你可能无法修复它，不如换一个新锁。(就像每次登录都会忘记密码一样，至少我一直都这样做，这是使用哈希的常见领域)。

．.． 我猜在这种情况下，你可以把彩虹算法称为锁匠。

希望事情好转=)

哈希和加密/解密技术的基本概述如下。

散列:

如果你再次哈希任何纯文本，你不能得到相同的纯文本 散列文本中的文本。简单地说，这是一个单向的过程。

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加密和解密:

如果你加密任何纯文本与密钥再次你可以 通过使用相同(对称)/不同(不对称)密钥对加密文本进行解密来获得相同的纯文本。

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更新: 解决编辑问题中提到的问题。

1. When to use hashes vs encryptions Hashing is useful if you want to send someone a file. But you are afraid that someone else might intercept the file and change it. So a way that the recipient can make sure that it is the right file is if you post the hash value publicly. That way the recipient can compute the hash value of the file received and check that it matches the hash value. Encryption is good if you say have a message to send to someone. You encrypt the message with a key and the recipient decrypts with the same (or maybe even a different) key to get back the original message. credits

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2. 是什么使哈希或加密算法不同(从理论/数学层面)，即什么使哈希不可逆 (没有彩虹树的帮助)

Basically hashing is an operation that loses information but not encryption. Let's look at the difference in simple mathematical way for our easy understanding, of course both have much more complicated mathematical operations with repetitions involved in it Encryption/Decryption (Reversible): Addition: 4 + 3 = 7 This can be reversed by taking the sum and subtracting one of the addends 7 - 3 = 4 Multiplication: 4 * 5 = 20 This can be reversed by taking the product and dividing by one of the factors 20 / 4 = 5 So, here we could assume one of the addends/factors is a decryption key and result(7,20) is an encrypted text. Hashing (Not Reversible): Modulo division: 22 % 7 = 1 This can not be reversed because there is no operation that you can do to the quotient and the dividend to reconstitute the divisor (or vice versa). Can you find an operation to fill in where the '?' is? 1 ? 7 = 22 1 ? 22 = 7 So hash functions have the same mathematical quality as modulo division and lose the information.

学分

哈希函数将可变大小的文本转换为固定大小的文本。

来源:https://en.wikipedia.org/wiki/Hash_function

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PHP中的哈希函数

哈希将字符串转换为哈希字符串。见下文。

散列:

$str = 'My age is 29';
$hash = hash('sha1', $str);
echo $hash; // OUTPUT: 4d675d9fbefc74a38c89e005f9d776c75d92623e

密码通常以散列表示形式存储，而不是以可读文本的形式存储。当终端用户希望访问受密码保护的应用程序时，必须在身份验证过程中提供密码。当用户提交密码时，有效的身份验证系统接收密码并对给定的密码进行散列。将此密码哈希与系统已知的哈希进行比较。在平等的情况下，允许访问。

DEHASH:

SHA1是单向哈希。这意味着你不能去散列。

但是，您可以强制使用散列。请参见:https://hashkiller.co.uk/sha1-decrypter.aspx。

MD5是另一种哈希。MD5散列器可以在这个网站上找到:https://www.md5online.org/。

为了阻止对哈希的蛮力攻击，可以给一个盐。 在php中，您可以使用password_hash()来创建密码散列。 函数password_hash()自动创建一个盐。 使用password_verify()对密码哈希进行验证(使用salt)。

// Invoke this little script 3 times, and it will give you everytime a new hash
$password = '1234';  
$hash = password_hash($password, PASSWORD_DEFAULT);  

echo $hash; 
// OUTPUT 

$2y$10$ADxKiJW/Jn2DZNwpigWZ1ePwQ4il7V0ZB4iPeKj11n.iaDtLrC8bu 

$2y$10$H8jRnHDOMsHFMEZdT4Mk4uI4DCW7/YRKjfdcmV3MiA/WdzEvou71u 

$2y$10$qhyfIT25jpR63vCGvRbEoewACQZXQJ5glttlb01DmR4ota4L25jaW

一个密码可以由多个哈希表示。 当使用password_verify()使用不同的密码哈希值验证密码时，该密码将被接受为有效密码。

$password = '1234';  

$hash = '$2y$10$ADxKiJW/Jn2DZNwpigWZ1ePwQ4il7V0ZB4iPeKj11n.iaDtLrC8bu';  
var_dump( password_verify($password, $hash) );  

$hash = '$2y$10$H8jRnHDOMsHFMEZdT4Mk4uI4DCW7/YRKjfdcmV3MiA/WdzEvou71u';  
var_dump( password_verify($password, $hash) );  

$hash = '$2y$10$qhyfIT25jpR63vCGvRbEoewACQZXQJ5glttlb01DmR4ota4L25jaW';  
var_dump( password_verify($password, $hash) );

// OUTPUT 

boolean true 

boolean true 

boolean true

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加密函数通过使用加密密钥将文本转换为无意义的密文，反之亦然。

来源:https://en.wikipedia.org/wiki/Encryption

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PHP加密

让我们深入研究一些处理加密的PHP代码。

- Mcrypt扩展-

加密:

$cipher = MCRYPT_RIJNDAEL_128;
$key = 'A_KEY';
$data = 'My age is 29';
$mode = MCRYPT_MODE_ECB;

$encryptedData = mcrypt_encrypt($cipher, $key , $data , $mode);
var_dump($encryptedData);

//OUTPUT:
string '„Ùòyªq³¿ì¼üÀpå' (length=16)

解密:

$decryptedData = mcrypt_decrypt($cipher, $key , $encryptedData, $mode);
$decryptedData = rtrim($decryptedData, "\0\4"); // Remove the nulls and EOTs at the END
var_dump($decryptedData);

//OUTPUT:
string 'My age is 29' (length=12)

——OpenSSL扩展——

Mcrypt扩展在7.1中被弃用。并在PHP 7.2中删除。 应该在php 7中使用OpenSSL扩展。请看下面的代码片段:

$key = 'A_KEY';
$data = 'My age is 29';

// ENCRYPT
$encryptedData = openssl_encrypt($data , 'AES-128-CBC', $key, 0, 'IV_init_vector01');
var_dump($encryptedData);

// DECRYPT    
$decryptedData = openssl_decrypt($encryptedData, 'AES-128-CBC', $key, 0, 'IV_init_vector01');
var_dump($decryptedData);

//OUTPUT
string '4RJ8+18YkEd7Xk+tAMLz5Q==' (length=24)
string 'My age is 29' (length=12)

当涉及到传输数据的安全性时，即双向通信，你使用加密。所有加密都需要密钥

当涉及到授权时，您使用哈希。哈希中没有键

Hashing takes any amount of data (binary or text) and creates a constant-length hash representing a checksum for the data. For example, the hash might be 16 bytes. Different hashing algorithms produce different size hashes. You obviously cannot re-create the original data from the hash, but you can hash the data again to see if the same hash value is generated. One-way Unix-based passwords work this way. The password is stored as a hash value, and to log onto a system, the password you type is hashed, and the hash value is compared against the hash of the real password. If they match, then you must've typed the correct password

为什么哈希是不可逆的:

哈希是不可逆的，因为输入到哈希的映射不是1对1的。 有两个输入映射到相同的哈希值通常被称为“哈希碰撞”。出于安全考虑，“好的”哈希函数的属性之一是在实际使用中很少发生冲突。

Use hashes when you only need to go one way. For example, for passwords in a system, you use hashing because you will only ever verify that the value a user entered, after hashing, matches the value in your repository. With encryption, you can go two ways. hashing algorithms and encryption algorithms are just mathematical algorithms. So in that respect they are not different -- its all just mathematical formulas. Semantics wise, though, there is the very big distinction between hashing (one-way) and encryption(two-way). Why are hashes irreversible? Because they are designed to be that way, because sometimes you want a one-way operation.

加密和哈希算法的工作原理类似。在每种情况下，都需要在比特之间制造混乱和扩散。简而言之，混淆是在密钥和密文之间创建一个复杂的关系，扩散是在传播每个比特的信息。

许多哈希函数实际上使用加密算法(或加密算法的原语)。例如，SHA-3候选Skein使用threfish作为底层方法来处理每个块。不同之处在于，它们不是保留每个密文块，而是破坏性地、确定性地合并在一起，形成固定的长度