Hey guys! Here is a guide to Introduction to Cryptography: Part 3, How to encrypt secret messages like Alan Turing, the best cryptographer.

Shift-Code

A shift-code is the method of encrypting in which we hide the original message by shifting each alphabet. Each alphabet is shifted either left or right to a specific distance, and that distance is known as “Key”. The key can either be positive (+ve) or negative (-ve) depending on the direction of shifting. For better understanding, we will be using “Shifting table” which looks like this.

Shifting Table

A shifting table has 2 columns, plain-text and shift. The plain-text dosen’t change with the shift but shift column does. The table looks like the above image when no shifting has been done. Now let’s do shifting with “+1”.

“+1” means that every letter of the shift column will move to it’s right by 1. The direction of the movement is determined by the sign of the key. “+” means “right” and “-” means “left”. Now let’s see how a “+1 Shift table” looks like.

+1 Shift table

You will see that every letter has been shifted to the right by 1 and the last letter comes to the first position. Now let’s see how “+3 Shift Table” looks like.

+3 Shift Table

You will see that every letter has been shifted to it’s right by 3. Now let’s try “+3 Shift table” to encrypt a message.

Encryption

Message : YOU ONLY LIVE ONCE Key: +3

Now to encrypt the message, start with each letter and replace it with the letter in the plain-text column. For example, the first letter (Y) will be replaced by letter (B) and the second letter (O) will be replaced by letter (R) and so on. Hence after encrypting the message looks like this.

Message : BRX RQOB OLYH RQFH

Now to make it more complicated, you can use 5-letter grouping, nulls, and synonyms. After using 5-letter grouping, the above message looks like this.

Message : BRXRQ OBOLY HRQFH

Decryption

Now to decrypt the message Now to encrypt the message, start with each letter and replace it with the letter in the shift column.

Homework-for-you!

Message : QEBOB’ PKLQE FKDXJ XKZXK KLQAL LKZBE BXZZB MQPQE BCXZQ QEXQQ EBOBF PKLDL AQPLD

Key : ( -3 )

HINT 1 : 4 Nulls. No synonyms.

Hint 2 : Don’t Breathe (2016)

Don’t Breathe (2016)

Comment the decoded message!!
Giveaway: Whoever will be the first to decode the message will get any one ebook of his/her choice!!

Part 4 of this interesting cryptography for beginners’ guide will soon be posted on MathCompt. Stay tuned!

Reference : Break the Code: Cryptography for Beginners by Bud Johnson