6.01 Lecture Notes - Lecture 5: Authenticated Encryption
22 May 2016
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Document Summary
Sometimes we want to speak of the relationship between x and y without a particular x and y in mind. We can do this by de ning a function : (x) = x + 6. We can do the same thing with lti systems by de ning system functionals. We will refer to y/x as the system functional. It characterises the operation of a system, independent of the particular input and output signals involved. It is functional in the sense that it is itself an operation which can be applied to arbitrary input signals. We can specify system functions for each of our system primitives. A gain element is governed by operator equation y = kx, for constant k, so its system functional is. A delay element is governed by operator equation y = rx, so its system functional is. We have three basic composition operations: sum, cascade, and feedback.
