如何使ios UDID更短但仍然唯一 [英] How can I make ios UDID shorter but still unique enlough

问题描述

我想使iOS设备的UDID小于或等于15个字符.

I want to make the UDID of a iOS device to less than or equal to 15 characters.

我正在将基于Symbian的客户端-服务器软件移植到iOS.服务器端使用IMEI(15位数字)来标识客户端电话.现在在iOS上，UDID太长(40个十六进制数字).由于要最大程度地减少服务器程序或数据库的更改，因此需要将UDID存储在varchar(15)中.

I am porting a Symbian based client-server software to iOS. The server side uses IMEI (15 digits)to id a client phone. Now on iOS, UDID is too long(40 hex digits). As I want to minimize the change of server program or DB, I need to store the UDID in a varchar(15).

因此，有任何方法可以使UDID较短，但仍然具有唯一性.如果我还可以从缩短的字符串中获取UDID，那就更好了.

So it's there any way to make the UDID shorter but still unique enlough. It could be much better if I can also get the UDID from the shorted string.

推荐答案

您可以将十六进制数字转换为20个Latin-1字符(≤0xff)或10个Unicode

You could convert the hex digits into 20 Latin-1 characters (≤0xff) or 10 Unicode BMP characters (≤0xffff).

如果varchar(15)可以接受Unicode BMP字符，那么我们就完成了.

If that varchar(15) can accept Unicode BMP characters, then we are done.

否则，您可以从那20个Latin-1字符中砍掉最后5个字符.UDID实际上是某些设备唯一值的 SHA-1哈希，该值可以被认为是相当随机的，并且数字是均匀分布的.因此，使用15个Latin-1字符，减少的UDID应该能够表示256 ¹⁵ 〜10 ³⁶ 设备，这远远不够.

Otherwise, you could chop the last 5 characters from that 20 Latin-1 characters. The UDID is in fact a SHA-1 hash of some device-unique values, which can be considered quite random and the digits are uniformly distributed. Therefore, with 15 Latin-1 characters the reduced UDID should be able to represent 256¹⁵ ~ 10³⁶ devices, which is much more than enough.

实际上，即使您仅从UDID中获取15个十六进制字符，它也已经可以表示约10 ¹⁸ 个设备.

In fact, even if you just take 15 hex characters from the UDID it could already represent ~ 10¹⁸ devices.

请注意，后两种方法是有损的，即无法从15个字符中获取完整的UDID.

Note that the last 2 methods are lossy, i.e. there is no way you could get the complete UDID from the 15 characters.

这篇关于如何使ios UDID更短但仍然唯一的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！