962 reputation
58
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location Waterloo, Canada
age 29
visits member for 3 years
seen Jan 20 '13 at 4:30

I am a PhD student with an interest in theoretical cryptography and mathematical tools used for cryptanalysis.


Nov
19
awarded  Yearling
Sep
24
awarded  Autobiographer
Nov
19
awarded  Yearling
Sep
23
awarded  Necromancer
Nov
19
awarded  Yearling
Sep
21
awarded  Custodian
Apr
9
comment Does encrypting twice using the same block cipher produce a security weakness?
I don't disagree with your comment, but I disagree with the formulation of your answer which for the first time gives an indication that you need to keep the keys independent if you want to use the same cipher text again. I just figured out that I was a bit hasty in making the second comment. You can construct an artificial PKC which is secure on one encryption, but leaks least (most) significant bits when doubly encrypted with the same key.
Apr
9
comment Does encrypting twice using the same block cipher produce a security weakness?
"as long as the keys you chose to encrypt a second time are independent of the keys you use the first time" This is not right, encryption keys are usually long lived keys. In fact, your statement questions the semantic security of the PKC in multiple message model. The second paragraph holds only for information theoretic security and that is because of Shannon's lower bound on the size of the key length.
Apr
4
comment ECC algorithm pollard's $\rho$ complexity
@VineetMenon: Complexity of an algorithm is always measured in terms of input size. In group-theoretic algorithms, the input is group and so it is measured by the order of the group that defines the group. Same for the graph. You define the complexity of a graph-theoretic algorithm in terms of the size of the graph, which is the number of vertices and the number of edges. If you have a sparse graph, then you just specify the number of vertices, edges are considered to be $O(n)$. For a general graph, you need both edges and vertices as for any connected graph, $\Omega(n) \leq E(G) \leq O(n^2).$
Apr
3
comment ECC algorithm pollard's $\rho$ complexity
The Handbook of Applied Cryptography says on Page 92 that it is $O(n^{1/4})$. I am not sure now where this poly-log factor came in to the picture!
Apr
3
comment ECC algorithm pollard's $\rho$ complexity
Can you give more details on why $poly \log$ factor is there? I don't understand what efficiency has to do with it. Thanks in advance!
Apr
3
revised ECC algorithm pollard's $\rho$ complexity
added 135 characters in body
Apr
3
answered ECC algorithm pollard's $\rho$ complexity
Apr
3
comment Trouble with diffie-hellman groups
$O(2^{256})$ is still $O(1)$.
Mar
31
comment Can you make a hash out of a stream cipher?
The negative vote down, can you state the reason why you are not satisfied with the answer?!
Mar
31
comment Can you make a hash out of a stream cipher?
If you will look at the security requirement in an universal hash function, you will notice the difference from the well-known security requirements of cryptographic hash functions, viz collision resistance. The reason why UOWHF were introduced was to construct much efficient signature scheme without relying on stronger properties like collision resistance.
Mar
29
revised Can you make a hash out of a stream cipher?
added 146 characters in body
Mar
29
answered Can you make a hash out of a stream cipher?
Mar
20
answered Order Preserving Encryption for Numeric Data Values
Mar
17
revised Is this fixed length MAC unforgeable?
Made it more readable with latex entries instead of text style entry.