Caesar cipher technique was founded by Julius caesar. Before looking at the caesar cipher program in java with output for encryption and decryption, first, we need to understand the terms plaintext and ciphertext.
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“caesar cipher” Code Answer’s. Javascript by Fylls on Aug 17 2020 Donate. A cipher is a method for encrypting a message, intending to make it less readable. As for the Caesar cipher, it's a substitution cipher that transforms a message by shifting its letters by a given offset. Let's say we want to shift the alphabet by 3, then letter A would be transformed to letter D, B to E, C to F, and so on.

What is plaintext and ciphertext?

Caesar Cipher in Java. GitHub Gist: instantly share code, notes, and snippets.
What they're hinting at is that you need to keep your original text intact. Don't add anything to it. Instead, create another string for the cipherText. Those are the terms in this problem domain: 'plain text' is the unencoded string, 'cipher text' is the encoded string.

plaintext is the input message given by user. In other words, message that needs to be encrypted.

Caesar Shift Cipher Java Code

ciphertext is the encrypted message. In other words, message after applying the caesar cipher technique.
What is Caesar cipher?
Caesar cipher is one of the simplest encryption technique. It is also known as the shift cipher, Caesar's cipher, Caesar shift or Caesar's code. Caesar cipher is a type of substitution cipher.
By using this cipher technique we can replace each letter in the plaintext with different one a fixed number of places up or down the alphabet.
For example :
With right shift of 3:
plaintext : ABCDEFGHIJKLMNOPQRSTUVWXYZ
ciphertext : DEFGHIJKLMNOPQRSTUVWXYZABC
With left shift of 3:
plaintext : ABCDEFGHIJKLMNOPQRSTUVWXYZ
ciphertext : XYZABCDEFGHIJKLMNOPQRSTUVW
With right shift of 2:
plaintext : Java Hungry Blog
ciphertext : Lcxc Jwpita Dnqi
As you can see for the above example 'Java Hungry Blog' each character in plain text is shifted by 2 as J become L , a become c , v become x and so on.
Note : You can use either left shift or right shift but not both in same text.
If we want to see Caesar cipher in mathematical way, then formula to get encrypted letter will be :
e = (x + n) mod 26
where,
n is the number of positions we need to shift plaintext characters
x is the place value of original letter
e is the place value of encrypted letter
On the other hand, we will use the below formula to decrypt each letter.
e = (x - n) mod 26
Pseudo Code for Caesar Cipher

Input : String plaintext
Input : An integer between 0 and 25 representing the right shift of the character or,
Traverse each character in the plaintext one at a time
Transform the given character depending on encryption or decryption.
print the ciphertext.

Simple Caesar Cipher Program in Java for Encryption Code

Output :
Input the plaintext message : Java Hungry Blog
Enter the value by which each character in the plaintext message gets shifted : 2

Caesar Cipher Java

ciphertext : Lcxc Jwpita Dnqi
Simple Caesar Cipher Program in Java for Decryption
Output :
Input the ciphertext message : Lcxc Jwpita Dnqi
Enter the shift value : 2
decrypt message : Java Hungry Blog
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Image Credits : Cepheus [Public domain], from Wikimedia Commons

Caesar Cipher Java Code With Output

Matt_Crypto [Public domain], via Wikimedia Commons