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Base64 Notation

Created on · Last Modified on

Base64
  • is an encoding between (a subset of ASCII characters) ↔ (sequences of 6 bits). In other words, each Base64 digit represents exactly 6 bits of data)

Base64 Table

Decimal

Binary

Base46

Decimal

Binary

Base64

Decimal

Binary

Base64

Decimal

Binary

Base64

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

=

Output Padding

The final == sequence indicates that the last group contained only one byte, and = indicates that it contained two bytes. The example below illustrates how truncating the input of the above quote changes the output padding:

INPUT

OUTPUT

Text

# of Chars

# of Bits

Base64 Text

# of Chars

# of Bits

Padding

pleasure

8

64

cGxlYXN1cmU=

12

72

1

pleasur

7

56

cGxlYXN1cg==

12

72

2

pleasu

6

48

cGxlYXN1

8

48

0

pleas

5

40

cGxlYXM=

8

48

1

plea

4

32

cGxlYQ==

8

48

2

Encoding/Decoding Base64

encode

echo -n ‘input’ | openssl base64

echo -n ‘hello’ | base64

openssl base64 -in plain.txt -out base64.txt

decode

echo -n ‘aGVsbG8=’ | base64 —decode

base64 —decode base64.txt > plain.txt