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location Peacedale, RI
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visits member for 3 years, 1 month
seen Sep 5 at 13:11

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.

Aug
23
comment Nonlinearity of the J-K Flip Flop
@DW: I'm curious about your comment that "I'm unlikely to do better than existing state-of-the-art schemes: what do you think you know about me that would lead you to make such a broad statement? Seems rather presumptuous on your part, no? Hello?
Jul
26
comment Secure way to store fixed size string of digits
@BradW: Yes, having gigabytes of easy storage gives you the luxury of being able to use random 256bit (or more) strings as unbreakable passwords.
Jul
25
comment Secure way to store fixed size string of digits
@BradW: Sorry Brad, you are right, I did not read all the comments, my bad.
Jul
23
comment Secure way to store fixed size string of digits
Store the information on a memory stick and keep the stick in your pocket until you need to enter it into your system.
Apr
26
comment Nonlinearity of the J-K Flip Flop
@grieu, Nice work, answer accepted. You are the "hardest working man in cryptography !
Apr
26
comment Nonlinearity of the J-K Flip Flop
@DW , Yes I am aware of how hard it is, but I like the challenge. But now that I am retired, its either design something new or watch "Gilligan's Island" re-runs. Oh, and by the way, if I were you, I wouldn't bet against me ;-)
Apr
25
comment Nonlinearity of the J-K Flip Flop
So let me ask this question: if the J-K flip flop was correlation-immune, it could be considered a strong cryptographic combining function?
Apr
25
comment Nonlinearity of the J-K Flip Flop
OK < thanks for the info, this is interesting. According to some papers I've read bent functions have to have an even number of variables, so according to your analysis, the flip flop can't have the same nonlinearity as the bent functions. I will wait for more answers here, hopefully someone will enlighten us.
Apr
9
comment Convert m-Sequence into a de Bruijn Sequence
Thank you fgrieu but I am only interested in designing my own CSPRNG. I only study other designs to see what makes them strong (or fail !). It the reason I took up cryptography as a hobby. :-D
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
How about another solution? Make a generator consisting of three LFSR's , the outputs of which are XOR'd together , but each LFSR has its own LFSR as a random clock. Sure you will make the key length greater but the added clocking complexity will make attacks like the edit distance attack computationally infeasible. Who knows, maybe some clever mathematician will show that breaking this generator is NP Complete by showing a reduction to 3-SAT. ;-)
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
A feedback function with a 62 input NOR gate is going to be way too slow for my purposes :-(
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
Wow, how did you find this? You are fast!!!
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
Just what I was looking for, you are the best. Not sure what "adding an XOR term equal to the NOR of the outputs of the n-1 flip flops" means??? Say I have a 63 bit register, for an m-sequence I will be tapping tap locations 62 and 63 with a single XOR gate for my feedback function. What am I adding to this to get the de Bruijn sequence?
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
Nice work but this not show me the electronic real-world circuit for inserting the zeros in the right places! You can't make an actual ASG without a schematic :-(
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
I don't understand why Gunther says in the paper "it is easy to convert an m-sequence into a deBruijn sequence. To me easy means simple. If you read some of the papers on generating deBruijn sequences, the syntheses are very complicated!!
Apr
8
comment Convert m-Sequence into a de Bruijn Sequence
@fgrieu: My thinking is that Gunther is alluding to a shift register with some kind of nonlinear feedback function consisting of XOR gate(s) with some other nonlinear gate(s), AND, OR, some combination thereof.
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.