ccna after b tech cse

ccna after b tech cse.Another example of a permutation cipher is a fence cipher (railfencecipher) o In this permutation, the words are spelled in a fence-like manner, i.e., using where rows are parallel, with some letters in the front row and some in the back row. For example, a fenceline cipher using key 3 requires three lines to be used in creating the encryption code.To read the message, it needs to be read up and down along the fence on a diagonal.F... .K... .T... .A... .T.. .N..L.N.E.S.A.T.C.A.D.W..Modern encryption algorithms, such as the Data Encryption Standard (DES) and the Triple Data EncryptionStandard (3DES), still use permutations as part of the algorithm.7.1.2.3 Substitution CipherA substitution cipher is a substitution of one letter for another. In their shortest form, replacement passwords retain the frequency of letter occurrences in the original message.The Caesar password is a simple replacement password. A different key is used each day to adjust the alphabet. For example, if the key for the day is 3, the letter A is shifted three positions to the right, resulting in the use of the letter D instead of the letter A in the encoded message, the letter E will replace the letter B, and so on. If the key of the day is 8, A becomes I, B becomes J, and so on.Since the whole message depends on the same single key shift, the Caesar cipher is called the monoalphabetic substitution cipher. For this reason, multi-alphabetic ciphers were invented, such as the Virginia cipher. This method was first proposed by GiovanBattistaBellaso in 1553, but was later wrongly attributed to the French diplomat and cryptographer Blaise deVigenere.The Virginia cipher is based on the Caesar cipher, with the difference that it uses a different multi-letter key shift for each plaintext letter when encrypting the body. The different key shifts are identified using a shared key between the sender and the receiver. The use of the Virginia Cipher Table allows encryption and decryption of plaintext messages.To demonstrate how the Virginia Cipher Table works, assume that the shared key used by the sender and receiver consists of these letters: SECRETKEY. the sender uses this key to encode the plaintext "FLANK EASTATTACKAT DAWN".