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The main purpose of the encoding is to convert an eight bit content into a readable ASCII string based on an alphabet which contains only letters, capitals, numbers and a few special math sign.
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 y
The alphabet can be read and used easily in the following format:
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
The main usage areas of the encoding:
- at mailing (mime)
- when using web server authentication
The mailing example is usually well known, but less people know that the normal web server authentication also uses this encoding. This authentication type is also known as Basic authentication, what must be used only over a secure (https) channel, because of the reversibility of the encoding model. It means that the user name and password goes through the channel as a clear text information.
Encoding - how to
The encoding is very simple: take three byte (24bit), put them next to each other and slice the string into four pieces of six bit pieces. Find the values of those pieces in the alphabet and you are almost ready now. If you have "broken fragments" at the end, fill those with the (pad) character.
Base64 on NOWAN
Base64 on the Internet
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