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Jul
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Jul
19
revised Are there asymmetric cryptographic algorithms that are not based on integer factorization and discrete logarithm?
I meant encryption as opposed to signatures etc
Jul
19
revised Are there asymmetric cryptographic algorithms that are not based on integer factorization and discrete logarithm?
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Jul
19
answered Are there asymmetric cryptographic algorithms that are not based on integer factorization and discrete logarithm?
Jul
19
comment Tactics available to help prove security of a new system?
I'll be the bad cop and say that if (1) you've already designed the cipher and only now are thinking about security, (2) are new to cryptanalysis and (3) you think a 4096 bit key is good — in fact if just one of these things — you are already in over your head. I don't want to discourage you and sometimes learning by doing is the best way but designing secure encryption schemes is very hard and requires years of expertise. (I say this as someone who myself would never dream of designing a block cipher or hash function.)
Jul
18
comment Why is there an enormous difference between SAT solvers?
This would be better suited on CSTheory SE. I think it is on topic for Crypto, but you will certainly get a better response there.
Jul
17
comment Reduction from signatures to encryption?
Nice answer. I agree with your caveats regarding my cheat and RSA. (I have a few comments when at keyboard not on my phone).
Jul
17
comment Reduction from signatures to encryption?
(1) Right it is not a reduction from any signature scheme, only ones with the condition that verification is not possible without the verification key. See fine print. (2) the adversary seeing the message only can make a selective forgery and obtain the same signature, assuming forgeries are easy and signature is deterministic. It only works under assumption that existential is easy and selective is hard.
Jul
17
revised Reduction from signatures to encryption?
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Jul
17
answered Reduction from signatures to encryption?
Jul
14
comment Are there any tools for expressing the cipher operations as a system of equations?
Part of the "art" of algebraic attacks is finding the appropriate field to embed the operations into. I would suspect if an automated tool were to be implemented (none to my knowledge), it wouldn't be very useful at finding "nice" representations. For example with AES, some operations are cleanly representable in GF(2) while others in GF(2^8). You can embed everything into GF(2^8) (e.g, big encryption scheme BES) but the representation gets messy.
Jul
14
revised Current mathematics theory used in cryptography/coding theory
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Jul
13
comment How to provide secure “vanity” bitcoin address service?
I see now that it is addr = (ver||RIPEMD-160(SHA-256(key)))||(SHA-256(SHA-256((ver||RIPEMD-160(SHA-256(key))‌​)))) where ver is version and key is the public key and the second component is only the first 4 bytes.
Jul
13
comment How to provide secure “vanity” bitcoin address service?
I see now the link to the spec, although not a spec of the exact formatting of the ECDSA key. Addresses contain a "version" field. If this is not checked or used by the clients, you could iterate on it (maybe in addition to the share of the secret key since version is only a byte) with only the cost of the hash (instead of a point multiplication, addition, and hash) per iteration.