Question

Exercises 28-55 are problems or shortanswer questions. Using a Caesar cipher, shifting three letters to the right, encrypt the message "WE ESCAPE TONIGHT."

Short answer

The encrypted message is 'ZH HVFDPS WRQLJKW.'.

Step-by-step solution

Understanding the Caesar Cipher

The Caesar cipher is a type of substitution cipher in which each letter in the plaintext is shifted a certain number of places down the alphabet. In this case, we are using a shift of three letters to the right.

Shift Each Letter

To encrypt the message 'WE ESCAPE TONIGHT.', we need to shift each letter three places to the right. Appendix non-letter characters like spaces and periods remain unchanged.

Encrypt the First Word

The first word is 'WE': - W shifted three places becomes Z. - E shifted three places becomes H. So, 'WE' becomes 'ZH'.

Encrypt the Second Word

The second word is 'ESCAPE': - E becomes H. - S becomes V. - C becomes F. - A becomes D. - P becomes S. - E becomes H. Thus, 'ESCAPE' becomes 'HVFDPS'.

Encrypt the Third Word

The third word is 'TONIGHT.': - T becomes W. - O becomes R. - N becomes Q. - I becomes L. - G becomes J. - H becomes K. - T becomes W. - The period remains unchanged. So, 'TONIGHT.' becomes 'WRQLJKW.'

Compile the Encrypted Message

Put all the encrypted words together with spaces to form the complete encrypted message: 'ZH HVFDPS WRQLJKW.'

Key concepts

Understanding Substitution Ciphers

Substitution ciphers are a simple method of encryption, where each unit of the plaintext is replaced with another entity according to a fixed system. The units can be letters, pairs of letters, or groups of letters. Each letter in the message is systematically swapped with a different letter from the alphabet.
The Caesar cipher, a popular type of substitution cipher, switches or substitutes each letter in the plaintext with another. A key factor in substitution ciphers is the method of substitution used, as this determines how secure the message is.
It's a straightforward yet effective way to keep information safe from unauthorized access, particularly suited for simple applications such as practice exercises and educational purposes.

The Process of Encryption

Encryption is the process of converting plaintext into a coded format, known as ciphertext, to protect the message from unauthorized access. In the context of the Caesar cipher, encryption involves replacing each letter in the original message with a letter a fixed number of spaces down or up the alphabet.
This process ensures that the original message content is unreadable without the corresponding decryption key, which in this case, is the number of positions each letter is shifted. By using this simple encryption, a message can be sent securely over potentially unsecured channels, since only those with the decryption key can understand it.

Deciphering Plaintext

Plaintext refers to the original, unencrypted message that is intended to be communicated before undergoing encryption. It is the readable and understandable text that anyone can interpret without any decryption key.
In the case of a Caesar cipher, the plaintext is prepared to undergo transformation into ciphertext by substituting each character based on the cipher's rules. For example, with the phrase "WE ESCAPE TONIGHT", each letter will be moved to three positions to the right, yielding a fully encrypted message that appears scrambled to those unaware of the cipher used.

How Shift Ciphers Operate

Shift ciphers are a subset of substitution ciphers where the entire alphabet is shifted by a set number of places. This shift dictates how each letter in the plaintext is transformed to the ciphertext.
In the Caesar cipher, a classic example of a shift cipher, each letter in the plaintext is replaced by another that is a fixed number away in the alphabet.

• If you're shifting to the right, each letter moves further down the alphabet.
• If you run out of letters, the alphabet wraps around to the beginning.
• The shift must be the same for every letter.

For example, a shift of three to the right means each letter is replaced by the letter three spaces down, transforming 'A' to 'D', 'B' to 'E', and so on. This shifting mechanism is what makes the cipher both simple to implement and relatively straightforward to break without strong keys.