5,415 reputation
11123
bio website people.scs.carleton.ca/~clark
location Ottawa, Canada
age 33
visits member for 3 years, 2 months
seen Jan 5 at 22:55

Postdoctoral fellow interested in authentication and cryptographic voting.


Aug
8
awarded  Taxonomist
Jul
12
awarded  Yearling
Apr
29
awarded  Nice Answer
Feb
12
awarded  Enlightened
Feb
12
awarded  Nice Answer
Aug
12
revised Bitcoin Research
Fixed link
Jul
26
awarded  Nice Question
Jul
12
awarded  Yearling
Jun
26
comment How is SSL secure from rogue Certificate Authorities?
In basic HTTPS, there is no protection against this attack. And it has been conducted in real life. However, there are a number of proposals to address this attack that have reached various stages of deployment but generally require either the client or the server to opt-in. For a history of these attacks and a list and evaluation of solutions, see this paper: people.scs.carleton.ca/~clark/papers/2013_sp.pdf (In particular, the first 8 rows in Table 1)
Mar
25
comment Can Elgamal be made additively homomorphic and how could it be used for E-voting?
Reading between the lines of what you are asking, the answer is no. Elgamal can handle both multiplication and addition, but you cannot mix the two operations on any given ciphertexts. You must decide when you encrypt to lock the ciphertext into only doing addition or only doing multiplication. The ability to do both is a "fully homomorphic" cryptosystem, of which there are some, but they are mainly theoretical and too slow to be practical. One efficient scheme, BGN, allows a single multiplication and as many additions as you want.
Feb
15
revised Encrypting a key with the same key
added 19 characters in body
Feb
15
answered Encrypting a key with the same key
Jan
16
comment Why is proof-by-reduction needed (for Elgamal proof of security, for example)?
@Maeher is correct. What is amiss is that you are not considering all the values (that are functionally dependent on x,r,m) that you have available. As for a step-by-step proof, see: shoup.net/papers/games.pdf (Section 3). And read the whole paper if you want more intuition into how to structure proofs.
Dec
4
awarded  Good Answer
Oct
16
comment Can Elgamal be made additively homomorphic and how could it be used for E-voting?
I don't know of any publications that directly compare Paillier with Elgamal in Gq or with ECC; although I haven't look too hard either. It is just accepted as folk wisdom I guess.
Sep
21
awarded  Custodian
Sep
18
reviewed Approve suggested edit on Random oracle model proofs and programmability
Sep
11
comment What is a “rewinding argument”?
It is a little long, but I illustrate it in my answer to another question here: crypto.stackexchange.com/a/1412/64
Sep
10
revised Are picture files “random enough” to be usable as a one-time pad?
deleted 1 characters in body
Sep
10
answered Are picture files “random enough” to be usable as a one-time pad?