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visits member for 1 year, 10 months
seen Nov 6 at 23:47

Sep
17
comment Finding algorithm: desire RSA's uniqueness and ECDSA's space efficiency
ECDSA signatures can be made to enjoy the uniqueness property you require. See crypto.stackexchange.com/questions/851/…
Sep
16
comment How secure is this use of Ziv-Lempel encoding?
Distinguishing two strings seems trivial for an adversary. If the encodings are the same then they are the same and if different then different. Also the "sort prefix" enables one to work out the orderings of the encoded values. If some corresponding decoded values are known then bounds can be put on the unknown decoded strings. So then one can guess the input values. This seems obvious enough from a cursory reading of the patent and seems to answer the question.
Sep
16
comment Scalar multiplication of elliptic curve point by a fraction
@user3768186 $P$ is just an implementation detail. It's not a relevant group property for this purpose. If you had two elliptic curves with the same order but different $P$ you would divide points by a fixed number on the different curves by multiplying by the same number.
Sep
16
comment Pollard's Rho - Constructing the random function
Please add some references to the "extensive articles" so I can check them out.
Oct
6
comment Reversing N CRC steps
I understand. Thanks. K.G can be justifiably proud of his answer. I would caution that I have encountered functions used as CRCs in some applications which do not behave exactly K.G describes.
Sep
3
comment Elliptic Curve Cryptography Encryption Results
I misspoke about ECIES. But jecc (which looks quite poor) sends one side of a ECDH key agreement and then appends the plaintext xor'ed with the hash of the shared key. This is a ElGamal encryption. See jecc.cvs.sourceforge.net/viewvc/jecc/jecc/elliptic/… It looks like it'll fall over if you encrypt more bytes than the length of their hash function outputs.
Sep
3
comment Elliptic Curve Cryptography Encryption Results
This is all rubbish. RSA does not involve any randomness but is not "trivially breakable". Secondly,the ciphertext in RSA can be the same length as the plain text. Thirdly ECIES results in longer ciphertexts without any symmetric usage. For shame whoever marked this as +1!
Jul
11
comment What is the fastest elliptic curve operation f(P) in affine coordinates such that f^n(P)=P only if n is large?
This is not the GLV method - it's just using an efficiently computable endomorphism which is well known. Also, the solution described does not avoid the inversion required to produce an affine point. Finally, I'm not sure what's so "complex" about the multiplication by j!
Jun
2
comment Can i modify data “protected” by a CRC16?
If you post 100 bytes and identify which ones you want changed to what and which ones you don't care about I'll do a demo!
Jun
2
comment Can i modify data “protected” by a CRC16?
If you XOR two 100 byte strings with valid CRCs then the result has a valid CRC (possibly with a tweak if the CRC is inverted). You can calculate the values using Gaussian Elimination mod 2 without having to understand any extra maths. This works because addition mod 2 has essentially the same features as normal addition. But as @CodesInChaos says, you need to be allowed to change at least 16 bits of the rest of the 100 bytes to some arbitrary values to "fix up" the CRC.
May
26
comment What is the fastest elliptic curve operation f(P) in affine coordinates such that f^n(P)=P only if n is large?
Post a comment with some sort of contact details (bitcointalk?) if you want my help.
May
24
comment What is the fastest elliptic curve operation f(P) in affine coordinates such that f^n(P)=P only if n is large?
I have some experience with Bitcoin's curve and I'm very confident that you will be unable to avoid an inversion for your problem as stated. I'm also quite confident that the restrictions you have specified above are more restrictive than are really necessary. Perhaps you can let us know whether you are a) trying to break the curve, b) generate vanity addresses, c) implementing some deterministic wallet scheme or d) implementing transactions which third parties can't link to an address.
May
24
comment What is the fastest elliptic curve operation f(P) in affine coordinates such that f^n(P)=P only if n is large?
I bet this is a Bitcoin-related question, in which case although people say it uses a Koblitz curve it is in fact not one. I think I have a good candidate solution for your problem but it works for a composite modulus and only if the group order is kept secret. If that's useful then let me know. If you're working in affine coordinates and you want to generate new points without inversions then you're probably limited to the Frobenius endomorphism.
May
9
comment RSA leak bits to factor N
You'd have to look at semismoothness probabilities in the vicinity of p and q to see if you could just search. I believe my idea is likely to win because there's the opportunity to do work on the sending side to encode the information and then more work on the receiving side whereas just leaking bits from $p$ requires the receiver to do all the work. If you could allow the primes to be not chosen uniformly at random but at random from a particular distribution which should have no effect on security then coming up with a suitable curve should be easy using complex multiplication.
May
7
comment What does $(\mathbb{Z}_n^*)^2$ mean?
How about a link to the paper? Is it about cryptography?
Apr
29
comment Adding and multiplication in jacobian coordinates
This is the relevant page of the Explicit-Formulas Database (thanks @CodesInChaos)
Apr
13
comment ElGamal: Generation of “g” value?
I have experienced people being quite negative about efficiency gains from having $g=2$. I haven't investigated so I have no opinion. Also, I found abc's answer to this post which would lead people (wrongly) to believe that $g=2$ is insecure for signatures in all cases. Perhaps you may care to leave a comment on the linked question to set the record straight for posterity. You have the gravitas I do not.. (yet!)
Apr
13
comment ElGamal: Generation of “g” value?
However, if you look at Appendix A.2 of FIPS 186-3 (the Digital Signature Standard) you will find a more comprehensive treatment of similar issues which boils down to pretty much the same thing.
Apr
12
comment ElGamal: Generation of “g” value?
If your maths knowledge is such that you can't see the truth of this when it's pointed out to you then the best solution is for you to brush up on your maths rather than for me to find someone who agrees with me.
Apr
9
comment ECKS-PS algorithm: searching in encrypted data; bilinear maps
Looking through your first page of notes (which I don't find easy to read) I notice that you appear to have e(i,j)=53^(i*j) mod 59 where I would normally read e to be some suitable paring computation on an elliptic curve. I presume you believe you're allowed to make this substitution to make thing simpler but it's not clear to me that it's actually going to work. Is this something you can justify?