Cipher Caesar

Alfeo told you how easy it is to break a Caesar cipher. But if you use several Caesars by turn, then the cipher becomes unbreakable Or so the sagacious Belaso believed and later authorities have agreed. The only thing you need to establish in advance with your correspondent is the order in which you will use the alphabets. No Well, let us attempt an example. A little farther down the page write the sentence,... 

Plaintext Shift or Caesar Ciphers. The simplest ciphers are plaintext shift ciphers or Caesar Ciphers (so named because they were used by Julius Caesar [23]). This type of cipher is created by uniformly shifting the letters in the alphabet over a certain number of spaces. 

While these two ciphers work, they are not reliable as they can be broken very easily. This is where mathematics gets involved. Mathematics can be used to create sophisticated ciphers that are virtually impossible to break. To begin this discussion, we will first see how a cipher, very similar to a plaintext shift or Caesar cipher, can be obtained mathematically by using some of the number theoretic concepts introduced earlier in this chapter. 

Plaintext Shift or Caesar Ciphers Revisited. Recall the plaintext shift cipher presented earlier (see Figure 2.7). This cipher motivates the use of mathematics in cryptography. 

The coded message YMJ HTU MFX GJJS GWTPJS has been intercepted. A plaintext shift (Caesar cipher) wa.s used to generate the message. Determine the specific plaintext shift used and what the plaintext message is,... 

Luciano, D., and Prichett, G., Ciyplology From Caesar Ciphers to Public-Key Cryptosystems, College Mathematics Journal, 18(1), 1987, 2-17. 

The most common type of cipher in ancient times was the substitution cipher. This was the type of cipher employed by Julius Caesar during the Gallic Wars, by the Italian Leon Battista Alberti in a device called the Alberti Cipher Disk described in a treatise in 1467, and by Sir Francis Bacon of Great Britain. In the 1400 s, the Egyptians discovered a way to decrypt substitution ciphers by analyzing the frequency of the letters of the alphabet. Knowing the frequency of a letter made it easy to decipher a message. 

Codes and ciphers have been used since the beginning of recorded time, when humans drew figures on a cave wall to communicate ideas. During the Gallic Wars, Julius Caesar devised one of the first substitution ciphers by printing the ciphertext alphabet with the letters moved four places to the left under the plaintext alphabet. 

There are few different types of encryption methods substitution, transposition, and one-time pad cipher. One of the oldest ciphers is substitution cipher, known as Caesar cipher, which substitutes every symbol with another from its group. For example A with D, B with G, and so on. This is very easy to analyze and break with common letter statistics. Transposition cipher preserves... 

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