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 Oct 6 revised Curve parameter for hyperelliptic curve cryptography? deleted 5 characters in body Oct 6 answered Reversing N CRC steps Oct 6 answered Curve parameter for hyperelliptic curve cryptography? 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! Aug 31 revised How can I take advantage of repeated patterns in non random RSA prime factors? added quote Aug 31 answered How can I take advantage of repeated patterns in non random RSA prime factors? Jul 11 answered Which area of Maths should I pursue? 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 awarded Commentator 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 9 answered How to derive formulas for addition and multiplication in Jacobian coordinates May 7 comment What does $(\mathbb{Z}_n^*)^2$ mean? How about a link to the paper? Is it about cryptography? May 7 answered RSA leak bits to factor N May 7 answered Solving a discrete logarithm using GDlog