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location Peacedale, RI
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visits member for 2 years, 11 months
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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.

Apr
8
asked Convert m-Sequence into a de Bruijn Sequence
Jan
14
comment Can a LFSR be cryptographically secure?
Please be aware that there is an error in the schematic shown in Fig.2 in the Gunther paper "Alternating Step Generator controlled by deBruijn Sequences. The AND gate controlling the clock of the lower shift register is missing an input inverter on the input coming from the deBruijn register. If the circuit was made without the inverter the clocking could not alternate.
Jan
13
comment How to judge if my work is meaningful in cryptography?
@Alex, Just my two cents worth: take your result to a college professor who works in cryptography (hopefully someone in your area) and have him /her critique it before you try and take a "big step" like submitting a paper to a professional journal or a conference.
Dec
25
comment What is the best (thoroughly covering) textbook for application of LFSRs in cryptography?
@Thomas Pornin: It may be premature to be writing-off LFSR's for several reasons. There are several PRNG's based on LFSR's that we have no polynomial time algorithms for breaking (Alternating Step Generator for one). Also nonlinear feedback shift registers is still a relatively new field whose algebraic properties are still not completely understood , so it is a rich field to explore (my opinion).
Dec
11
comment Blum-Blum-Shub Cryptosystem
Richard Feynman once quipped "Nobody understands quantum physics". Well, nobody understands the BBS Cryptosystem either!(kidding). Actually this algorithm is very slow and there are other problems with using it ( see Ritter's Cryptoglossary for a good exposition on this). My advice is to not waste your time with it. Use something else like the Alternating Step Generator as the key generator for a stream cipher. There is no public cryptanalysis (break) for this generator as long as each shift register is 128 bits long.
Dec
9
awarded  Enthusiast
Dec
1
comment XOR cipher Pseudo-random key strength
@Daniel: How are you "randomly selecting " the predefined characters and how is this table of characters generated? If as you say you don't care that the Mersenne is not cryptographically secure, why worry about the quasi-randomness of your key?
Dec
1
comment XOR cipher Pseudo-random key strength
@Daniel: Your question is related to the object known as a randomness extractor( see Wiki). So I think your question should evolve to something along the lines of "given two sources of weak randomness (1000,5000) and an extraction function A , is applying the function A to (1000) going to create a string of characters with more or less statistical bias than a string created by applying A to (5000).
Nov
30
comment XOR cipher Pseudo-random key strength
Also, there is no known way to mathematically define the "strength" of any particular key string so your question can't be answered on this basis alone.
Oct
31
comment How do I prove that this PRNG is easily distinguished from a random sequence of numbers (modulo m)?
If you can prove that this generator ( or any PRG is indistinguishable from a truly random distribution, you have proven that P is not equal to NP. Go collect your million dollar prize from the Clay Mathematics Institute.
Sep
7
awarded  Popular Question
Aug
27
comment Testing the Fortuna random number generator?
@jochen: If you want to test the cryptographic properties you have to see if anyone can "break the generator" by using the output bits to find the secret key.
Aug
11
answered Testing the Fortuna random number generator?
Jul
12
comment Cryptographic Challenge: How to Say Something Confidentially to Snowden?
There is no reliable substitution for meeting someone in person and exchanging a private key which contains message and identity authentication bits ( I would use 128 bits for each, 256 if you are paranoid and/or smoke weed), in a OTP system or a stream cipher with a known cryptographically secure psuedorandom generator.
Jul
8
comment Are stream ciphers no longer considered by NIST?
Why the Alternating Step Generator is not used more is beyond me, there has been no public cryptanalysis(break) of this generator since it was published in 1987,26 years ago, that is long time to stand up to public scrutiny. It may be un-crackable as long as the key length is large enough, it is an amazingly simple algorithm.
Jun
20
comment Proofs of security methodologies
There are no cryptographic primitives that have proof of security unless you can show that P is not equal to NP. Just showing a reduction from some cryptographic primitive to a known hard problem in NP does not mean that the primitive is secure, you also have to prove that the problem in NP is computationally intractable. That means separating P from NP. This is well known in theoretical computer science.
Jun
15
comment Will D-Wave's quantum computers ruin classical encryption?
See Scott Aaronson's blog to see the latest info on D-Wave. Apparently D-Wave has NOT demonstrated any real quantum computing yet.
Jun
11
comment Acceptable assumptions when proving security
@WatsonLadd: Yes you can reduce the algorithm to a known hard problem but that is not proving that either is hard, to PROVE hardness ( and therefore proving security) is to prove that P is not equal to NP.
Jun
10
comment Acceptable assumptions when proving security
@WatsonLadd: There is no such thing as provable security : proving some communication system is unconditionally secure means separating the complexity classes P and NP, one of the Clay Mathematics Institute Millenium challenges.
Jun
3
comment Are there any hand ciphers not obsoleted by computer cryptanalysis?
@Luke Sheppard: Just curious , what would be your motivation for wanting a hand-generated cipher in the first place? The only scenario I can think of would be in prisons, where gangs usually communicate to their fellow gang-bangers by some kind of handwritten code.