Java-Base64
某钱包分享链接泄漏手机号码了，链接
安全问题很重要啊
简介
BASE64 编码是一种常用的字符编码，在很多地方都会用到。但base64不是安全领域下的加密解密算法。能起到安全作用的效果很差，而且很容易破解。
他核心作用应该是传输数据的正确性，有些网关或系统只能使用ASCII字符。Base64就是用来将非ASCII字符的数据转换成ASCII字符的一种方法，而且base64特别适合在http，mime协议下快速传输数据。
Java实现
在Java 8在java.util包下面实现了BASE64编解码API，java.util.Base64
Basic编码
是标准的BASE64编码，用于处理常规的需求
输出的内容不添加换行符，而且输出的内容由字母加数字组成
// 编码
String asB64 = Base64.getEncoder().encodeToString("some string".getBytes("utf-8"));
System.out.println(asB64);
// 输出为: c29tZSBzdHJpbmc=
// 解码
byte[] asBytes = Base64.getDecoder().decode("c29tZSBzdHJpbmc=");
System.out.println(new String(asBytes, "utf-8"));
// 输出为: some string
URL编码
如果是使用基本的编码器，那么输出可能会包含反斜线“/”字符，但是如果使用URL编码器，那么输出的内容对URL来说是安全的。
String urlEncoded = Base64.getUrlEncoder().encodeToString("subjects?abcd".getBytes("utf-8"));
System.out.println("Using URL Alphabet: " + urlEncoded);
// 输出为:Using URL Alphabet: c3ViamVjdHM_YWJjZA==
编码标准： RFC 4648 page7
>Josefsson Standards Track [Page 7] > >RFC 4648 Base-N Encodings October 2006 > > > Table 2: The "URL and Filename safe" Base 64 Alphabet > > Value Encoding Value Encoding Value Encoding Value Encoding > 0 A 17 R 34 i 51 z > 1 B 18 S 35 j 52 0 > 2 C 19 T 36 k 53 1 > 3 D 20 U 37 l 54 2 > 4 E 21 V 38 m 55 3 > 5 F 22 W 39 n 56 4 > 6 G 23 X 40 o 57 5 > 7 H 24 Y 41 p 58 6 > 8 I 25 Z 42 q 59 7 > 9 J 26 a 43 r 60 8 > 10 K 27 b 44 s 61 9 > 11 L 28 c 45 t 62 - (minus) > 12 M 29 d 46 u 63 _ > 13 N 30 e 47 v (underline) > 14 O 31 f 48 w > 15 P 32 g 49 x > 16 Q 33 h 50 y (pad) = > >5. Base 64 Encoding with URL and Filename Safe Alphabet > > The Base 64 encoding with an URL and filename safe alphabet has been > used in [12]. > > An alternative alphabet has been suggested that would use "~" as the > 63rd character. Since the "~" character has special meaning in some > file system environments, the encoding described in this section is > recommended instead. The remaining unreserved URI character is ".", > but some file system environments do not permit multiple "." in a > filename, thus making the "." character unattractive as well. > > The pad character "=" is typically percent-encoded when used in an > URI [9], but if the data length is known implicitly, this can be > avoided by skipping the padding; see section 3.2. > > This encoding may be referred to as "base64url". This encoding > should not be regarded as the same as the "base64" encoding and > should not be referred to as only "base64". Unless clarified > otherwise, "base64" refers to the base 64 in the previous section. > > This encoding is technically identical to the previous one, except > for the 62:nd and 63:rd alphabet character, as indicated in Table 2. >``` 标准的Base64并不适合直接放在URL里传输，因为URL编码器会把标准Base64中的“/”和“+”字符变为形如“%XX”的形式，而这些“%”号在存入数据库时还需要再进行转换，因为ANSISQL中已将“%”号用作通配符。 为解决此问题，可采用一种用于URL的改进Base64编码，**它在末尾填充“=”号，并将标准Base64中的“+”和“/”分别改成了“-”和“_”，**这样就免去了在URL编解码和数据库存储时所要作的转换，避免了编码信息长度在此过程中的增加，并统一了数据库、表单等处对象标识符的格式。 ### MIME编码 使用基本的字母数字产生BASE64输出，而且对MIME格式友好：每一行输出不超过76个字符，而且每行以“\r\n”符结束。java StringBuilder sb = new StringBuilder(); for (int t = 0; t < 10; ++t) { sb.append(UUID.randomUUID().toString()); } byte[] toEncode = sb.toString().getBytes(“utf-8”); String mimeEncoded = Base64.getMimeEncoder().encodeToString(toEncode); System.out.println(mimeEncoded); ```
延伸点：MIME编码