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=