William Hird

76 reputation

bio	website	notyet;)
	location	Peacedale, RI
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Electronics Engineer, Amateur Cryptographer with interests in designing real random and psuedorandom bit generators.

"Randomness is like a box of chocolates; you never know what you are going to get"

                                                                   Forrest Gump Jr.

"You can't use mathematical means to create true randomness but you can use mathematical means to stretch a short truly random bitstream into a binary string of virtually infinite length that is indistinguishable from the uniform distribution, the distinguisher being a Universal Turing Machine". John Von Neumann Jr.

"It's trivial to make a Turing machine that fools all other Turing machines into "thinking" that they are looking at an unpredictable uniform distribution. Here is the schematic."

                                                                   Alan Turing Jr.

	76 reputation	bio	website	notyet;)	visits	member for	1 year, 9 months
6 badges		location	Peacedale, RI		seen	4 hours ago

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May 17	comment	Is AES really used for Top Secret stuff? Hey Paulo, how come you never welcomed me to CST when I first signed on? I feel left out :-(
May 1	comment	Should I trust CipherCloud? Why was this closed, it has fifteen upvotes so I guess it has sparked reasonable interest. Doesn't seem to be any worse than some of the other questions posted on this site(mine included);-)
Feb 19	comment	Are asymptotic lower bounds relevant to cryptography? @JoeZeng: Thanks Joe, we are being kicked out now but thanks for the nice discussion :-)
Feb 19	comment	Are asymptotic lower bounds relevant to cryptography? @JoeZeng: Joe, I think you might be confused: The strength of the one time pad comes from the randomness of the KEY, not from the "function", the function is just XOR ( or XNOR if you happen to be a natural contrarian) that mixes the plaintext with the key. The key is not the function.
Feb 19	comment	Are asymptotic lower bounds relevant to cryptography? @JoeZeng: The one time pad is a one way permutation: you are using a random key and an XOR gate to perform a permutation on the plaintext. A one way permutation is a kind of one way function, read the article in Wiki for one way functions. Also read the paper by Terry Ritter " The Efficient Generation of Cryptographic Confusion Sequences". Go to section 5.1 One Way Functions and see his quote about ALL strong cryptographic systems are essentially one way functions.
Feb 19	comment	Are asymptotic lower bounds relevant to cryptography? @JoeZeng: Hi Joe, ALL "unbreakable" cryptosystems are by definition one way functions. Its an open problem in theoretical computer science as to the relationship between one way functions and the P vs NP problem.. If you can prove that the one time pad cryptosystem has nothing to do with hard on average problems in NP, step up and write a paper on it and wait for the announcement of your Turing award.
Jan 29	comment	What is the most paranoid way to exchange messages? @JeremyDicaire: Why sad? Maybe they can fall in love, give up cryptography, have a child(Eve?), live happily ever after?(not necessarily in this that order) :-)
Jan 28	comment	What is the most paranoid way to exchange messages? Taking your question at face value, obviously the most paranoid way for Alice and Bob to communicate with perfect secrecy is for Bob and Alice to meet somewhere and whisper messages into each others ear.
Dec 4	comment	Bent Combining Functions I meant no disrespect to Mr. Carlet, I was suggesting that I have no way to verify that any emails I have received are actually from the real Mr. Carlet. You have misunderstood my comment.
Dec 4	comment	Bent Combining Functions @DW: You are right , I did not define what I meant by a bent sequence , I incorrectly assumed that a bent boolean function like the AND function when used as a combining function for psuedorandom sequences will produce a bent sequence. A novice error to be sure.
Dec 3	comment	Bent Combining Functions I'm not sure how your answer relates to my question. The AND function for two variables is bent according to Claude Carlet(he should know!) so if you use it to combine two m-sequence LFRS"s the output is a nonlinear representation of the input. Looking at the truth table for the AND function we see that three out of four lines of the table resolve to 0. So an attacker does not know if the 0 was caused by inputs {0,0} {0,1} or {1,0}. Of course the output will not be balanced but for my circuit I don't care about balance . Sorry if mis-named this sequence a "bent sequence".
Dec 3	comment	Bent Combining Functions @DW: nice answer but it does matter what I call the sequence if I am writing a paper that will be seen by experts . I want to be technically correct. Maybe there is no name designation for the sequence I described, why don't you invent a name for it, I will cite you in the paper ;-)
Nov 11	comment	Cryptanalysis of Linear Feedback Shift Registers Thank you, the answer was well worth the wait :-)
Nov 9	comment	Cryptanalysis of Linear Feedback Shift Registers @DW. You are right, I think my original question needs to be upgraded , I'll try to come up with a better question. Thanks.
Nov 8	comment	Cryptanalysis of Linear Feedback Shift Registers @DW: Lets just assume that an attacker can see the complete output of the generator and he knows everything about the generator; the register length, polynomial,ect. All the attacker doesn't know is the seed.
Nov 8	comment	Cryptanalysis of Linear Feedback Shift Registers @ DW : What do you mean by "noisy"observations of the LFSR sequence? In answer to your question as what problem I'm trying to solve: I'm trying to do what all cryptographers are trying to do: design a generator that no algorithm can crack, a one way function ;-)
Oct 26	comment	Because the algorithm is known, it is no longer a trade secret @Henno: I will just quote from the Wikipedia article on this matter: "Although Enigma had some cryptographic weaknesses, in practice it was only in combination with proceedural flaws, operator mistakes, captured key tables and hardware, that Allied cryptanalysts were able to be so successful." I might also like to add that I don't believe the official Bletchley Park story about how they "broke the code". Its too "pat", too "Hollywood", of course we will never really know what happened. Finis. :-)
Oct 22	comment	Because the algorithm is known, it is no longer a trade secret @John Deters: To be fair and accurate, Enigma was not broken because it was a weak algorithm, it was broken because it was not implimented correctly(human error).
Oct 10	comment	Avalanche noise RNG for one-time pad use I just read your link, it looks a lot like the old Intel RNG ( the new generator uses gate metastability to generate chaos). Given all the post-processing of the raw bits, it looks like it would be hard for an attacker to break it. But remember there are no guarantees of perfect randomness. To prove that a RNG is unpredictable is still an open problem.
Oct 10	comment	Avalanche noise RNG for one-time pad use It would be hard to give a reliable answer to your question without seeing the actual electronic schematic for this device. What kind of noise generators are used, how is the noise stream sampled, ect?