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

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

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。

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。

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

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

EncryptionThe Purpose of encryption is to transform data in order to keep it secret E.g (Sending someone a secret text that they only should able to read,sending passwords through Internet). Instead of focusing the usability the goal is to ensure the data send can be sent secretly and it can only seen by the user whom you sent. It Encrypts the data into another format of transforming it into unique pattern it can be encrypt with the secret key and those users who having the secret key can able to see the message by reversible the process. E.g(AES,BLOWFISH,RSA) The encryption may simply look like this FhQp6U4N28GITVGjdt37hZN Hashing In technically we can say it as takes a arbitary input and produced a fixed length string. Most important thing in these is you can't go from the output to the input.It produces the strong output that the given information has not been modified. The process is to take a input and hash it and then send with the sender's private key once the receiver received they can validate it with sender's public key. If the hash is wrong and did't match with hash we can't see any of the information. E.g(MD5,SHA.....)

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=)

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.