The XOR (Exclusive Or) gate is a logic in which an exclusive-or function is implemented between inputs. An XOR gate can have two or more inputs and then satisfies the exclusive-or function if one input corresponds to a logical one and the other input or inputs correspond to a logical zero
. If all inputs are logic zeros, the condition is not satisfied. Similarly, if all inputs were logical ones, it is not satisfied. This would then be a logical OR operation. Circuit-wise, an XOR gate is a combination of AND gate, OR
gateand NOT gate. The truth value of the XOR logic is "1" at the output only if either input represents "1". If both inputs are "1" at the same time, the output is "0", likewise if both inputs are "0". If one input is "1", then the output is also "1". This means that the output is "1" whenever the inputs are different, and is "0" whenever the inputs have equal logic states. Therefore, this logic is also called odd logic. The negated function of the XOR gate forms the XNOR gate
.antivalence between input states. It is particularly interesting for encryption, since it is bitwise oriented, it is particularly fast to implement. Circuit families for XOR gates are the 7486 in TTL
logicand 4030 in CMOS
. Exclusive-OR logic is used in computer engineering, but mainly in cryptography. In computing, it is found in the full adder of the Von Neumann calculator, where the carry is performed when two ones are added with an AND gate. In encryption, the exclusive OR function has a special significance, since the use of XOR functions makes it almost impossible to draw conclusions about the cryptoalgorithm.