是Md5加密对称还是不对称？ [英] Is Md5 Encryption Symmetric or Asymmetric?

问题描述

对于我的iPhone应用程序，苹果想知道我的密码加密（md5）是大于64位对称还是大于1024位对称。我没有能够在网上找到它，所以我想知道是否有人知道答案。此外，这是否被认为是适当的密码加密技术，或者我应该使用不同的？

For my iPhone application, Apple wants to know if my password encryption (md5) is greater then 64-bit symmetric or greater then 1024-bit symmetric. I have not been able to find it online, so I am wondering if anyone knows the answer. In addition, is this considered an appropriate encryption technology for passwords, or should I use something different?

感谢任何帮助！

推荐答案

MD5是一个散列函数，因此根据定义它是不可逆的。这不是加密（对称或不对称）的情况，它必须是可逆的才有用。

MD5 is a hashing function, thus by definition it is not reversible. This is not the case for encryption (either symmetric or asymmetric), which has to be reversible to be useful.

更准确地说，散列是单向函数，因为无限数量的输入可以映射到单个输出，因此不可能确定地获得导致给定输出的确切输入。

To be more precise, hashes are one-way functions, in that an infinite number of inputs can map to a single output, thus it is impossible to obtain the exact input, with certainty, that resulted in a given output.

但是，可以找到散列到相同输出的不同输入。这被称为冲突。

However, it may be possible to find a different input that hashes to the same output. This is called a collision.

一般来说，哈希密码而不是存储纯文本（甚至加密）是一个好主意。 （甚至更好，如果使用盐）但是，MD5已知的弱点（和大集合的彩虹表，有助于找到碰撞），因此它是一个好主意，切换到像SHA-1或SHA-2之一

Generally, hashing passwords instead of storing the plain text (even encrypted) is a good idea. (Even better if using a salt) However, MD5 has known weaknesses (and large collections of rainbow tables that aid in finding collisions), thus it would be a good idea to switch to something like SHA-1 or one of the SHA-2 family of hashes.

但是，为了回答你原来的问题，真的没有办法比较MD5或任何类型的加密哈希;他们没有等同物，因为它像比较苹果和橙子。

However, to answer your original question, there is really is no way to compare MD5 or any hash against any type of encryption; they have no equivalents because it's like comparing apples and oranges.

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