Base64和Base64url之间有什么区别？我在JSON Web Tokens等东西中看到这样的内容。
2个回答
123
Base64和Base64url都是将二进制数据编码为字符串形式的方法。您可以在此处阅读有关base64理论的内容。 Base64的问题在于它包含
下面是差异的图表：
+，/和=这些字符，在某些文件系统名称和URL中具有保留意义。因此，base64url通过将+替换为-，将/替换为_来解决此问题。尾部填充字符=在不需要时可以被省略，但在URL中，它最可能是% URL编码。然后，编码数据可以在URL中包含而不会出现问题。下面是差异的图表：
Index Base64 Base64Url
0 A A
1 B B
2 C C
3 D D
4 E E
5 F F
6 G G
7 H H
8 I I
9 J J
10 K K
11 L L
12 M M
13 N N
14 O O
15 P P
16 Q Q
17 R R
18 S S
19 T T
20 U U
21 V V
22 W W
23 X X
24 Y Y
25 Z Z
26 a a
27 b b
28 c c
29 d d
30 e e
31 f f
32 g g
33 h h
34 i i
35 j j
36 k k
37 l l
38 m m
39 n n
40 o o
41 p p
42 q q
43 r r
44 s s
45 t t
46 u u
47 v v
48 w w
49 x x
50 y y
51 z z
52 0 0
53 1 1
54 2 2
55 3 3
56 4 4
57 5 5
58 6 6
59 7 7
60 8 8
61 9 9
62 + -
63 / _
= (optional)
以下我将引用标准中的定义。
RCF 4648规范
4. Base 64 Encoding
The following description of base 64 is derived from 3, [4], [5], and [6]. This encoding may be referred to as "base64".
The Base 64 encoding is designed to represent arbitrary sequences of octets in a form that allows the use of both upper- and lowercase letters but that need not be human readable.
A 65-character subset of US-ASCII is used, enabling 6 bits to be
represented per printable character. (The extra 65th character, "=", is used to signify a special processing function.)The encoding process represents 24-bit groups of input bits as output strings of 4 encoded characters. Proceeding from left to right, a 24-bit input group is formed by concatenating 3 8-bit input groups. These 24 bits are then treated as 4 concatenated 6-bit groups, each of which is translated into a single character in the base 64 alphabet.
Each 6-bit group is used as an index into an array of 64 printable characters. The character referenced by the index is placed in the
output string.Table 1: The 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 + 12 M 29 d 46 u 63 / 13 N 30 e 47 v 14 O 31 f 48 w (pad) = 15 P 32 g 49 x 16 Q 33 h 50 ySpecial processing is performed if fewer than 24 bits are available at the end of the data being encoded. A full encoding quantum is
always completed at the end of a quantity. When fewer than 24 input
bits are available in an input group, bits with value zero are added
(on the right) to form an integral number of 6-bit groups. Padding
at the end of the data is performed using the '=' character. Since
all base 64 input is an integral number of octets, only the following cases can arise:(1) The final quantum of encoding input is an integral multiple of 24 bits; here, the final unit of encoded output will be an integral multiple of 4 characters with no "=" padding.
(2) The final quantum of encoding input is exactly 8 bits; here, the final unit of encoded output will be two characters followed by two "=" padding characters.
(3) The final quantum of encoding input is exactly 16 bits; here, the final unit of encoded output will be three characters followed by one "=" padding character.
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.
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) =
- Suragch
4
3
虽然这篇文章比较旧，但如果有人需要帮助的话，如果你使用的是.NET技术，你可以通过Brock Allen提供的System.IdentityModel.Base64Url类来进行Base64Url编码/解码。
/// <summary>
/// Base64Url encoder/decoder
/// </summary>
public static class Base64Url
{
/// <summary>
/// Encodes the specified byte array.
/// </summary>
/// <param name="arg">The argument.</param>
/// <returns></returns>
public static string Encode(byte[] arg)
{
var s = Convert.ToBase64String(arg); // Standard base64 encoder
s = s.Split('=')[0]; // Remove any trailing '='s
s = s.Replace('+', '-'); // 62nd char of encoding
s = s.Replace('/', '_'); // 63rd char of encoding
return s;
}
/// <summary>
/// Decodes the specified string.
/// </summary>
/// <param name="arg">The argument.</param>
/// <returns></returns>
/// <exception cref="System.Exception">Illegal base64url string!</exception>
public static byte[] Decode(string arg)
{
var s = arg;
s = s.Replace('-', '+'); // 62nd char of encoding
s = s.Replace('_', '/'); // 63rd char of encoding
switch (s.Length % 4) // Pad with trailing '='s
{
case 0: break; // No pad chars in this case
case 2: s += "=="; break; // Two pad chars
case 3: s += "="; break; // One pad char
default: throw new Exception("Illegal base64url string!");
}
return Convert.FromBase64String(s); // Standard base64 decoder
}
}
- Ross Brasseaux
1
网页内容由stack overflow 提供, 点击上面的可以查看英文原文，
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+和/之外，其他都是相同的，对吗？2.如果“-”掩盖了“+”，那么你如何区分它本身与掩盖“+”时的“-”？ - mfaanibase64url比base64更为普遍。您知道这是否属实吗？ - Zephaniah Grunschlag