Base64 Algorithm
Base64 is an algorithm for encoding byte data into ASCII string format (binary-to-text). The algorithm is the reverse, that is possible to convert the text back to a byte code without data loss. Base64 is very widely used in WEB technologies: to convert binary files into text for emails, for the conversion of graphic elements in HTML and CSS.
The Base64 algorithm is based on converting in groups of 3 bytes (3 * 8 bits = 24 bits) to a group of 6 bits (4 * 6 = 24 bits). Each 6-bit group is an index from 0 to 63, 64 in total, which is why the algorithm is called Base64. To convert to ASCII string format, the character set is used (according to RFC 4648 standard):
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
If there is not enough data to form a group of 3 bits, then the missing bits are filled with the symbol "="
Table of Base64 (RFC 4648)
Index | Binary | Char | Index | Binary | Char | Index | Binary | Char | Index | Binary | Char | |||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 | 000000 | A | 16 | 010000 | Q | 32 | 100000 | g | 48 | 110000 | w | |||
1 | 000001 | B | 17 | 010001 | R | 33 | 100001 | h | 49 | 110001 | x | |||
2 | 000010 | C | 18 | 010010 | S | 34 | 100010 | i | 50 | 110010 | y | |||
3 | 000011 | D | 19 | 010011 | T | 35 | 100011 | j | 51 | 110011 | z | |||
4 | 000100 | E | 20 | 010100 | U | 36 | 100100 | k | 52 | 110100 | 0 | |||
5 | 000101 | F | 21 | 010101 | V | 37 | 100101 | l | 53 | 110101 | 1 | |||
6 | 000110 | G | 22 | 010110 | W | 38 | 100110 | m | 54 | 110110 | 2 | |||
7 | 000111 | H | 23 | 010111 | X | 39 | 100111 | n | 55 | 110111 | 3 | |||
8 | 001000 | I | 24 | 011000 | Y | 40 | 101000 | o | 56 | 111000 | 4 | |||
9 | 001001 | J | 25 | 011001 | Z | 41 | 101001 | p | 57 | 111001 | 5 | |||
10 | 001010 | K | 26 | 011010 | a | 42 | 101010 | q | 58 | 111010 | 6 | |||
11 | 001011 | L | 27 | 011011 | b | 43 | 101011 | r | 59 | 111011 | 7 | |||
12 | 001100 | M | 28 | 011100 | c | 44 | 101100 | s | 60 | 111100 | 8 | |||
13 | 001101 | N | 29 | 011101 | d | 45 | 101101 | t | 61 | 111101 | 9 | |||
14 | 001110 | O | 30 | 011110 | e | 46 | 101110 | u | 62 | 111110 | + | |||
15 | 001111 | P | 31 | 011111 | f | 47 | 101111 | v | 63 | 111111 | / | |||
Padding | = |
Example with word "HELLO"
H | E | L | L | O | |||||||||||||||||||||||||||||||||||||||||||
72 | 69 | 76 | 76 | 79 | |||||||||||||||||||||||||||||||||||||||||||
0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | - | - | - | - | - | - |
18 | 4 | 21 | 12 | 19 | 4 | 60 | Padding | ||||||||||||||||||||||||||||||||||||||||
S | E | V | M | T | E | 8 | = |
HELLO -> SEVMTE8=