#CONTOH PROGRAM VIGENERE CIPHER SERIES#
#CONTOH PROGRAM VIGENERE CIPHER CRACK#

Even though the word RADIOLOGISTS is also a twelve-letter key that is easier to remember than DURIWKNMFICK, a cryptanalyst might anticipate that the cryptographer is using an English word as a key.ДЄttempting a brute-force attack using every English word in the dictionary is known as a dictionary attack. In fact, not using a word that can be found in the dictionary is best.

It can be any combination of letters of any length, such as the twelve-letter key DURIWKNMFICK. Choosing a Key That Prevents Dictionary AttacksДЄ VigenГЁre key doesnвЂ™t have to be a real word like PIZZA.

#CONTOH PROGRAM VIGENERE CIPHER CRACK#

With keys that are twelve or more letters long, it becomes impossible for a mere laptop to crack them in a reasonable amount of time. Table 18-2: Number of Possible Keys Based on VigenГЁre Key Length Table 18-2 shows how many possible keys there are for each key length. Once there are quadrillions of possible keys, the cipher would take a computer many years to break. The good news is that for every additional letter the key has, the number of possible keys multiplies by 26. Then it could try AAAAB, then AAAAC, and so on until it got to PIZZA. It would first try to decrypt the message using the key AAAAA and check whether the resulting decryption was in English. Eleven million keys are far too many for a human to brute-force, but a computer can try them all in just a few hours. PIZZA is a poor choice for a VigenГЁre key because it has only five letters. The more letters in the VigenГЁre key, the stronger the encrypted message will be against a brute-force attack. Using the VigenГЁre cipher with the key PIZZA (which is made up of the subkeys 15, 8, 25, 25, 0) encrypts the plaintext COMMON SENSE IS NOT SO COMMON into the ciphertext RWLLOC ADMST QR MOI AN BOBUNM. Table 18-1: Encrypting Letters with VigenГЁre Subkeys The integer for the plaintext letter and subkey (given in parentheses) are added together to produce the integer for the ciphertext letter. To encrypt the first C in the plaintext with the subkey P, encrypt it with the Caesar cipher using the subkeyвЂ™s corresponding numeric key 15, which results in the cipherletter R, and repeat the process for each letter of the plaintext by cycling through the subkeys. The plaintext is shown with the corresponding subkey that encrypts each letter underneath it. The following is the message COMMON SENSE IS NOT SO COMMON shown alongside the VigenГЁre key PIZZA.

Instead of encrypting the whole plaintext with one Caesar cipher, we apply a different Caesar cipher to each letter of the plaintext.ДЇigure 18-2: Caesar cipher keys and their corresponding letters Using the VigenГЁre cipher is the same as using multiple Caesar ciphers, as shown in Figure 18-1. When we get to the sixth letter of the plaintext, we return to the first subkey. The first subkey encrypts the first letter of the plaintext, the second subkey encrypts the second letter, and so on. For example, if we use a VigenГЁre key of PIZZA, the first subkey is P, the second subkey is I, the third and fourth subkeys are both Z, and the fifth subkey is A.

#CONTOH PROGRAM VIGENERE CIPHER SERIES#

The VigenГЁre key is a series of letters, such as a single English word, that is split into multiple single-letter subkeys that encrypt letters in the plaintext. Instead of using a numeric key between 0 and 25 as we did in the Caesar cipher, we use a letter key for the VigenГЁre. Unlike with the simple substitution cipher, frequency analysis alone will not defeat the VigenГЁre cipher. Because it uses more than one set of substitutions, the VigenГЁre cipher is a polyalphabetic substitution cipher.

Unlike the Caesar cipher, the VigenГЁre cipher has multiple keys. Using Multiple Letter Keys in the VigenГЁre Cipher Building strings using the list-append-join process

Contoh program vigenere cipher