Observation Station – Basic Encryption Algorithms 01

01

There are mainly seven types of Base encoding

They are Base16, Base32, Base64, Base58, Base85, Base91, Base100, and other variants such as Base62, Base45, etc. For Base encoding, you only need to remember their characteristics, and when you see the ciphertext, you should know what type of encryption it is.

Next, I will introduce some main Base encodings.

Base16 Encoding

Base16 encoding, also known as “hexadecimal encoding” or “Hex encoding”, is a method of representing binary data as hexadecimal digits and characters.

Encoding Process

1. Split the binary data into groups of 4 (since 4 bits can represent 16 different characters (2^4=16))

2. Map each group of four binary digits to the corresponding Base16 character.

3. If the binary data is not a multiple of 4, pad with 0 at the end.

The index table is as follows

Decoding Example Explanation

Next, try to decode this using a tool (or calculate it yourself)

68 65 6c 6c 6f 20 78 69 6e

Convert to Decimal

Convert to Corresponding Characters

Complete Process with Table

Using the formula:

Decimal Value = High Character Value × 16 + Low Character Value × 1

Hexadecimal Calculation Process Decimal
68	6 × 16 + 8 = 104	104
65	6 × 16 + 5 = 101	101
6c	6 × 16 + 12 = 108	108
6c	6 × 16 + 12 = 108	108
6f	6 × 16 + 15 = 111	111
20	2 × 16 + 0 = 32	32
78	7 × 16 + 8 = 120	120
69	6 × 16 + 9 = 105	105
6e	6 × 16 + 14 = 110	110

According to the ASCII table, convert the decimal values to corresponding characters:

Decimal ASCII Character Description
104	h	Lowercase h
101	e	Lowercase e
108	l	Lowercase l
108	l	Lowercase l
111	o	Lowercase o
32		Space
120	x	Lowercase x
105	i	Lowercase i
110	n	Lowercase n

Complete decoding process summary

Hexadecimal Decimal ASCII Character

68 104 h

65 101 e

6c 108 l

6c 108 l

6f 111 o

20 32 (space)

78 120 x

69 105 i

6e 110 n

Answer: hello xin

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Example Attempt

Next, try to decode this using a tool

71696e6762616e7a68616e6768656e6169636861

Please send the answer privately to the class leader

Base32 Encoding

Base32 is a method of encoding binary data into an ASCII string, using 32 printable characters (uppercase letters A-Z and digits 2-7) to represent 5-bit binary numbers

Encoding Process

1. Split the binary data into groups of 5 (like Base16, since 5 bits can represent 32 different characters (2^5=32))

2. Map each group of four binary digits to the corresponding Base32 character.

3. If the binary data is not a multiple of 5, pad with “=”

The index table is as follows

Decoding Example Explanation

Next, try to decode this using a tool (or calculate it yourself)

NBSWY3DPEBQW4===

Convert to5-bit Binary

Binary

Rearrange

Binary

Convert to Decimal

First, remove the padding character “=” from the Base32 characters, then convert to the corresponding decimal numbers in the index table

Base32 Corresponding Decimal Binary
N	13	01101
B	1	00001
S	18	10010
W	22	10110
Y	24	11000
3	27	11011
D	3	00011
P	15	01111
E	4	00100
B	1	00001
Q	16	10000
W	22	10110
4	28	11100

Concatenate all binary numbers in order

01101 00001 10010 10110 11000 11011 00011 10000 01100 00001 10100 10110 11100

(There are a total of 65 bits, but we padded three positions with “=”, so the effective binary is only 62 bits)

Discard the last three invalid digits and replace them with 0

01101 00001 10010 10110 11000 11011 00011 10000 01100 00001 10100 10110 11000

Rearrange in groups of eight

01101000 01100101 01101100 01101100 01101111 00100000 01100001 01101110

(Discard those that are less than eight bits)

Complete decoding process

Attached summary table

Eight-bit Binary Decimal ASCII
01101000	104	h
01100101	101	e
01101100	108	l
01101100	108	l
01101111	111	o
00100000	32	Space
01100001	97	a
01101110	110	n

Answer: hello an

Swipe left and right to see more

Example Attempt

Next, try to decode this using a tool

PJQWS3DBNF4WSYTFNE======

Please send the answer privately to the class leader

Base64 Encoding

Base64 is a method of encoding binary data using 64 printable characters, commonly used for transmitting or storing binary data in text protocols

Encoding Process

1. Split the binary data into groups of 6 (like Base16, since 6 bits can represent 64 different characters (2^6=64))

2. Map each group of four binary digits to the corresponding Base32 character.

3. If the length of the binary data is not a multiple of 3, one or two padding characters “=” can be used to complete it

The index table is as follows

[Note: Some variant questions may change the index table]

Example Explanation

Next, try to decode this using a tool (or calculate it yourself)

aGVsbG8geWk=

Convert to6-bit Binary

Binary

Rearrange

Binary

Convert to Decimal

Like Base32

Base64 Corresponding Decimal Binary
a	26	011010
G	6	000110
V	21	010101
s	44	101100
b	27	011011
G	6	000110
8	60	111100
g	32	100000
e	30	011110
W	22	010110
k	36	100100

Concatenate all binary numbers in order

011010 000110 010101 101100 011011 000110 111100 100000 011110 010110 100100

Rearrange in groups of eight

01101000 01100101 01101100 01101100 01101111 00100000 01111001 01101001

(Discard those that are less than eight bits)

Complete decoding process

Attached summary table

Binary Decimal ASCII
01101000	104	h
01100101	101	e
01101100	108	l
01101100	108	l
01101111	111	o
00100000	32	Space
01111001	97	y
01101001	110	i

Answer: hello yi

Swipe left and right to see more

Example Attempt

Next, try to decode this using a tool

eXVhbnNlbnFpZG9uZw==

Please send the answer privately to the class leader

02

Tool Introduction

Finally, here are some practical tools that can make encryption and decryption easier and faster

1. CyberChef Online Tool

(Some base encodings are not included)

Website: https://cyberchef.org/

2. Flowing with the Current

Needs to be downloaded, can be found by searching online, it also has many encryption and decryption tools

3. Others

You can also directly search for online decryption websites for a specific encoding, such as the bugku online tool.