A Caesar cipher with a shift of 3 means each letter is shifted 3 positions backward in the alphabet. When decrypting "Wklv lv d whvw phvvdjh," shifting each letter 3 positions back gives "This is a test message."
The Caesar cipher involves shifting each letter in the plaintext by a fixed number of positions in the alphabet. For example, with a shift of 3, "A" becomes "D," "B" becomes "E," and so on.
In the Vigenère cipher, the key repeats across the message. "K" corresponds to a shift of 10, "E" to a shift of 4, and "Y" to a shift of 24. Since the first letter in the ciphertext is "F," the shift is from the letter "K," which shifts "F" back by 10 letters, giving "E."
The Atbash cipher is a type of substitution cipher where the alphabet is reversed. "A" becomes "Z," "B" becomes "Y," and so on. The letter "M" becomes "N" when using the Atbash cipher because it is the 13th letter in the alphabet, and its reverse counterpart is also the 13th letter from the end.
In a substitution cipher, each letter of the plaintext is replaced by another letter (in this case, "L" becomes "X"). This process is called substitution, where the letters of the alphabet are systematically replaced by others.
