Use the Caesar cipher to unscramble the ciphertext LDPJR...

Use the Caesar cipher to unscramble the ciphertext
LDPJR LQJWR VSDLQ WRILJ KWDQD UPBZL
WKRXW DJHQH UDODQ GWKHQ FHWRW KHHDV
WWRIL JKWDJ HQHUD OZLWK RXWDQ DUPB
This statement is ascribed to Julius Caesar himself.

Key Concepts

Caesar Cipher

The Caesar cipher is a basic substitution cipher in which each letter in the plaintext is shifted by a fixed number of positions along the alphabet. It is one of the earliest and simplest methods of encryption, historically attributed to Julius Caesar, and serves as an introductory example of how encryption works.

Decryption

Decryption is the process of reversing the encryption to convert the ciphertext back into readable plaintext. In the context of a Caesar cipher, decryption is achieved by shifting the letters in the opposite direction by the same fixed number used during encryption.

Substitution Cipher

A substitution cipher replaces elements of the plaintext with corresponding elements from a fixed system, such as letters of the alphabet. The Caesar cipher exemplifies this technique by systematically substituting each letter with another letter located at a constant distance along the alphabet.

Encryption

Encryption is the method of converting original information, or plaintext, into an encoded version, or ciphertext, to protect the data from unauthorized access. Simple techniques like the Caesar cipher help illustrate fundamental principles of encryption, despite its vulnerability to basic cryptanalysis.

Transcript

00:01 All right, so this time we're giving this incredibly long message, and we are told that the cipher is going to be of the form f of p is equal to p plus k, mod 26.

00:22 All right, so that means our decryption cipher must be of the form p minus k mod 26.

00:40 Okay, and so how do we go about figuring that out? well, we're going to do a method that you've probably done by the time you reach this problem, where we look at the most common letters in this cipher.

00:53 And in this particular cipher, the most common letter happens to be m.

01:01 Okay.

01:05 And so we knew that m is going to be the 12th.

01:18 Okay, so m is the 12th letter, and we want to find a k by, taking 12 and subtracting a value of other common letters.

01:31 And so i've gone ahead and tried some of these other ones.

01:36 E is the first option is the most common.

01:39 It doesn't work.

01:40 T -a -o -i -n -s -h and r are the other most common letters.

01:45 And it turns out this cipher makes sense if we use i.

01:49 So we'll take i equals 8, and that means k is going to be equal to 12 minus 8.

01:56 Is four.

01:58 So we're going to take this cipher and use p minus four mod 26 to solve it.

02:15 All right.

02:16 So the first thing is to convert what we have into the numbers, and that ends up being 4 .17 to 22, 24, 9, 9.

02:42 12 612 8 17 23 15 and 2 and then 4 7 25 4 17 onto this next row so we get 23 8 8 6 11, 17, 18, 15, 18, 10, and 2, 12, 22, 12, 17, 7, 22, 12, 17, 7, 12, 12, 22, 23, 12, 12, 12, 12, 12, 22, 23, 12, 12, 17, 211, 4, 5, 15, 8...

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