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The XOR operator is extremely common as a component in more complex ciphers. By itself, using a constant repeating key, a simple XOR cipher can trivially be broken using frequency analysis. If the content of any message can be guessed or otherwise known then the key can be revealed.
The xor–encrypt–xor (XEX) is a (tweakable) mode of operation of a block cipher. In tweaked-codebook mode with ciphertext stealing , it is one of the more popular modes of operation for whole-disk encryption. XEX is also a common form of key whitening, and part of some smart card proposals. [1] [2]
On July 22, 1919, U.S. Patent 1,310,719 was issued to Gilbert Vernam for the XOR operation used for the encryption of a one-time pad. [7] Derived from his Vernam cipher, the system was a cipher that combined a message with a key read from a punched tape. In its original form, Vernam's system was vulnerable because the key tape was a loop, which ...
Say we send messages A and B of the same length, both encrypted using same key, K. The stream cipher produces a string of bits C(K) the same length as the messages. The encrypted versions of the messages then are: E(A) = A xor C E(B) = B xor C. where xor is performed bit by bit. Say an adversary has intercepted E(A) and E(B). They can easily ...
The most common form of key whitening is xor-encrypt-xor-- using a simple XOR before the first round and after the last round of encryption. The first block cipher to use a form of key whitening is DES-X , which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES .
To prevent this kind of attack, one can use the method provided by Bruce Schneier: [1] Generate a random pad R of the same size as the plaintext. Encrypt R using the first cipher and key. XOR the plaintext with the pad, then encrypt the result using the second cipher and a different (!) key.
Encrypt (K, data): use the underlying block cipher in encrypt mode on the 'data' string using the key K. Decrypt (K, data): use the underlying block cipher in decrypt mode on the 'data' string using the key K. XOR: Bitwise Exclusive-OR. Equivalent to bitwise addition without use of a carry bit. ||: Concatenation operator.
XOR can be used to swap two numeric variables in computers, using the XOR swap algorithm; however this is regarded as more of a curiosity and not encouraged in practice. XOR linked lists leverage XOR properties in order to save space to represent doubly linked list data structures.