Diferencia entre winzip y winrar2/11/2024 ![]() ![]() Your post will be removed permanently if flair is not added within one hour. If your post is not flaired it will not be reviewed. Hi butterballmd thank you for submitting to /r/Askscience. None of this really needed to be said, but I kinda just lurk sometimes until I see the word entropy in regards to data and pounce. For some compression schemes that work on a bit by bit level, this makes compression impossible. Still, it is then critical that the output of any encryption not do that. I put leak in quotation marks, because this does not necessarily mean that you can derive a subset of bits, just that where you once had 2 n different possible sequences, you can now determine the sequence belongs to a set 2 n / 2 nI(X Y) = 2 n(1-I(X Y)). In fact, lets say a n-bit source has all 2 n sequences as equally likely, for any encryption scheme which does not result in P(x|y) being 50/50 you will "leak" (at least) 2 nI(X Y), where I(X Y) = \sum_ P(x,y) \log_2 p(x,y)/(p(x) p(y) ). If P(x|y) is not 50/50 for every symbol by definition you are now leaking information (as one sequence set becomes more likely). For this reason now, consider if you had a bit sequence x n and encrypted bit sequence y n. Many different ways to implement, even theoretically possible to implement using error correction codes, but the end goal of all is to leak as little information as possible. There are many ways to do this of course and many approximations and methods, but what is important is that in the end you end up with 0s and 1s being nearly equally likely at the output.Įncryption on the other hand basically puts all the sequences into a big pot stirs it up and outputs another sequence. Such as a source which typically results in a sequence like 000010000011 has low entropy than a source which typically results in a sequence like 101010011010.Ĭompression is, in a broad sense, is about removing the redundancy of the data. To add on to this, by high entropy he refers to the redundancy in the data. We make our world significant by the courage of our questions and by the depth of our answers. For more open-ended questions, try /r/AskScienceDiscussion | Sign up to be a panelist!. ![]()
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |