Take the letter 'A', which is represented by 00011, and add it tothe letter 'B', represented by 11001.A bit-wise XOR operation yields 11010 which,in the, is the letter 'G'.In fact, each bit from the key tells us whether or not the correspondingbit from the plaintext should be inverted.By inverting these key-bits again, as shown above,the original character is revealed.Although 'Teletype' is actually a brand name of the Teletype Corporation,it has become a generic expression for. The systemis also known as Teleprinter, Teletypewriter and Telex.XOR = Exclusive OR.ExampleThe principle of the Vernam Cipher is perhaps easier understood bylooking at a message stored on a punched paper tape. In the examplebelow, we want to transmit the word HELLO which is stored on theplain text tape.We also have a pre-recorded key tape, with a series of randomcharacters; in this case the sequence AXHJB.The contents of the plaintext tape are now XOR-ed with thecontents of the key tape.The result (KMIVE) is shown here as the ciphertext tape.
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Vernam Cipher:Vernam Cipher works on binary data rather than letters, which give us a defense against frequency letters analysis because there's no statistical relationship between the plaintext and the ciphertext.The encryption algorithm in Vernam Cipher can be expressed as:Ci = PiāKiCi = ith binary digit of ciphertext.Pi = ith binary digit. Vernam cipher is a stream cipher where the original or plain data is XORed with a random (actually pseudorandom) stream of data of the same length to generate the encrypted data. When the stream of data used as key is truly random and used only once, it is called a one-time pad.
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