Last time I said that Caesar code was easily cracked, so many improvements were made on the basis of it.
Caesar code belongs to the translation transformation of the alphabet, and its general encryption formula is f (a) = (a k) MOD N, N is the number of letters in the character, and the value of K is 1 to 25. When k = 3, this transformation is Celebrous.
Another way is to change the order of the alphabet, also known as a multiplier transform, which generally encrypts F (a) = Ak MOD N, N is the number of letters in the character. Here, the value of K must be with N mutual monitone (i.e., the maximum number of conventions); otherwise periodic, different characters will produce the same encryption results. Such as: k = 5, n = 26, the transform formula is f (a) = (5 * a) mod 26
明文: Abcdefghijklmnopqrstuvwxyz cps: EJOTYDINSXCHMRWBGLQVAFKPUZ
Because Z is encoded 26, K and 26 mutual, so F (a) = (26 * k) mod 26 = 26, the plain text z is encrypted or it itself. Similarly, M (encoded 13) is the same.
If K = 2, K and 26 is not integrated, the same case occurs. Such as, f (1) = (1 * 2) MOD 26 = 2, f (14) = (14 * 2) MOD 26 = 2 ,? The ciphertexts of letters A and N are b, and cannot be determined by decryption formula Plan. Such a situation will also appear in B and O ... M and Z, which repeats the same encryption results in 13 cycles.
In conjunction with the above two transformations, it is also known as a linear transformation. f (a) = (a * k1 k2) MOD N, N is the number of letters in the character set, and the value of K must be with N-mutual. Such as K1 = 3, K2 = 2, n = 26
Plahemia: Abcdef cps: EHKNQT
The decryption of these three methods is very simple, but it has reached the effect of chaos. And as long as you know the key to get a cryptographic table, the method of decryption is also very simple.
