Hi folks, Assume for a moment that we have a random number generator which is non-uniform, and we are using it to generate a key.
What I'd like to do is characterize the work factor involved in brute-force search of the key space, assuming that the adversary has knowledge of the characteristics of the random number generator? The algorithm for this is simple: Let the array X represent the probabilities of the outcomes of the random number generator, sorted by probability, with x being the probability of the most probable value. Then, for a given fraction of the messages n (0 < n <= 1): i = 0 m = 0 while (m + x[i]) < n: m = m + x[i] i = i + 1 return (i - 1) + (n - m) / (m + x[i]) This return value represents the average number of decryption attempts required to guess the right key. If one wanted to round up, one could just return i instead of the last expression above, because the second term is always in (0, 1] I'm curious if there's a way to express this calculation as a mathematical formula, rather than an algorithm, but right now I'm just blanking on how I could do it. -- Obama Nation | My emails do not have attachments; it's a digital signature that your mail program doesn't understand. | http://www.subspacefield.org/~travis/ If you are a spammer, please email j...@subspacefield.org to get blacklisted.
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