Cryptographic Challenge: Base64 to Hex

Posted on October 7, 2018 by Administrator Posted in Computer Science, Computing Concepts, Cryptography

ChallengeBase64Hexadecimal

Your challenge is to write a piece of code, using the programming language of your choice, to code and to decode messages encrypted using Base 64 encoding and Hexadecimal (Base 16) encoding.

Your progamme will first ask the user if they want to encode or decode a message. It will then ask the user to enter either the plain text (using the base64 character set) or the ciphertext (hexadecimal).

Your program will then output the decoded (plaintext) or the encoded message (ciphertext).

For instance:
Plain: Code/Breaker Cipher: 0A875EFC1ADE6A47AB

The following diagram will help you understand how the conversion from Base 64 to Hexadecimal works:
cryptography-base64-hexadecimal

Code Breaking Challenge:
You will then be able to decrypt the following encoded message:

Cipher: Plain Text:

Base64

Base64 is a binary-to-text encoding scheme where each character (plaintext) is coded using 6 bits of data. Hence a base64 character set contains exactly 64 characters:

Index	Char	Index	Char	Index	Char	Index	Char
0	`A`	16	`Q`	32	`g`	48	`w`
1	`B`	17	`R`	33	`h`	49	`x`
2	`C`	18	`S`	34	`i`	50	`y`
3	`D`	19	`T`	35	`j`	51	`z`
4	`E`	20	`U`	36	`k`	52	`0`
5	`F`	21	`V`	37	`l`	53	`1`
6	`G`	22	`W`	38	`m`	54	`2`
7	`H`	23	`X`	39	`n`	55	`3`
8	`I`	24	`Y`	40	`o`	56	`4`
9	`J`	25	`Z`	41	`p`	57	`5`
10	`K`	26	`a`	42	`q`	58	`6`
11	`L`	27	`b`	43	`r`	59	`7`
12	`M`	28	`c`	44	`s`	60	`8`
13	`N`	29	`d`	45	`t`	61	`9`
14	`O`	30	`e`	46	`u`	62	`+`
15	`P`	31	`f`	47	`v`	63	`/`

Hexadecimal

Hexadecimal is a base-16 number system. The hexadecimal numbers are 0-9 and then use the letters A-F to represent the decimal values 10 to 15.

Each digit in hexadecimal can be coded in binary using 4 bits as follows:

Binary	Decimal	Hexadecimal
0000	0	0
0001	1	1
0010	2	2
0011	3	3
0100	4	4
0101	5	5
0110	6	6
0111	7	7
1000	8	8
1001	9	9
1010	10	A
1011	11	B
1100	12	C
1101	13	D
1110	14	E
1111	15	F

Extension Task

Using the same approach, we can encode message in a range of encoding schemes such as Hexadeximal (4-bits per character), Base32 (5 bits per character), Base64 (6 bits per character), Extended ASCII (8 bits per character).

You can now update your code to cater for a range of encoding/decoding techniques between all these encoding schemes.