Caesar Cipher – the easiest encryption method you should know
In cryptographic study, we know the simpliest way to conceal the information is by ’substitution’. You replace the original word/alphabet by another word/alphabetic ’systematically’. The word ’systemtically’ have to be in place because you need a way to decrypt the concealed message.
In Latin language system, we use a alphabet to replace another one sequentially as below:
A replaced by D
B replaced by E
C replaced by F
………………………. and so on and so forth.
In this way, a message originally written as
ATTACK STARTS ON SEVEN TONIGHT
becomes
DWWDFN VWDUWV ……………..
And the key is 3 for we ’shifted’ three alphabets for each alphabet.
So the decryption is easy, we just shift back the three alphabets in the reverse direction to decrypt the ciphertext.
This encryption method is too naive that an attacker can easily uncover the message by brute force attack. Why? It is because there are only 25 possible keys for this encryption. A can be shifted by at most 25 different positions and so is B, C and D, etc.
So an attacker can literally try all possible keys to break the encryption.
Other than that, can you think of another attack method that can uncover the plaintext encrypted by Caesar Cipher ?
It is Frequency Analysis Attack method…
July 8th, 2006 at 11:33 pm
[...] To improve Caesar Cipher Encryption, we can assign each alphabet with another one in an non-sequential manner. For example A can be mapped to D while B can be mapped to R, and so are the rest being mapped to a different alphabet. Recall that Caesar Cipher has a key space of 25, Monoalphabetic Substitution can have a key space of 26 x 25 x 24 x…….x 1, i.e. 26! (This time we have a different assumption, we assume that each alphabet can be mapped to itself). [...]