1. A receiver for securely obtaining a control word, the receiver comprising: a first memory configured for storing a transform function configured to receive a transformed control word and a seed and to migrate the transformed control word from an input transform space to an output transform space to obtain the control word using a mathematical transformation under control of the seed, wherein the control word is in a clear text form or in an encrypted form; a cache memory; and a cache control module configured to: intercept the transformed control word and the seed; search in the cache memory for the control word matching the transform function, the transformed control word and the seed; in response to the control word matching the transform function and the transformed control word and the seed is found in the cache memory, provide the control word in the cache memory to an output of the transform function without invoking the transform function; and in response to the control word matching the transform function and the transformed control word and the seed is not found in the cache memory, activate the transform function to transform the transformed control word into the control word, provide the transformed control word and the seed to an input of the transform function, obtain the control word from the transform function based on the transformed control word and the seed, and store the control word associatively with the transform function, the transformed control word and the seed in the cache memory.