5,495 reputation
11123
bio website people.scs.carleton.ca/~clark
location Ottawa, Canada
age 33
visits member for 3 years, 4 months
seen Jan 5 at 22:55

Postdoctoral fellow interested in authentication and cryptographic voting.


Jul
19
revised Are there asymmetric cryptographic algorithms that are not based on integer factorization and discrete logarithm?
added 55 characters in body
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?
added 175 characters in body
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
added 4 characters in body
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.
Jul
13
comment How to provide secure “vanity” bitcoin address service?
It would be possible to greatly improve the efficiency if you can find something in the preimage to tweak that does not require additional mathematical operations to be performed on it before hashing. However without an exact specification of the address generation, it is hard to say if there are any other fields or formatting that can be tweaked.
Jul
13
comment How to provide secure “vanity” bitcoin address service?
The article first says that addresses are simply the output of a hash, but then later says that they include some error correction which means they are not merely the output of a hash?
Jul
13
revised Current mathematics theory used in cryptography/coding theory
added 97 characters in body
Jul
13
answered Current mathematics theory used in cryptography/coding theory
Jul
13
revised Replacing the Rijndael S-Box?
added 205 characters in body
Jul
13
answered Replacing the Rijndael S-Box?
Jul
13
awarded  Organizer
Jul
13
revised Why use a 1-2 Oblivious Transfer instead of a 1 out of n Oblivious Transfer?
edited tags