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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 2 years, 9 months
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Apr
12
revised Difference between plain AES CTR and “CCM-style” CTR
edited tags
Apr
11
awarded  Deputy
Apr
10
comment Difference between plain AES CTR and “CCM-style” CTR
Unfortunately there isn't one standard CTR mode, different protocols use different ways of combining the counter with the IV and incrementing it.
Apr
10
comment Leak-proof protocol: is such a thing possible?
Another covert channel: timing
Apr
10
comment cryptography and use of python programming language
There are some nice libraries for python, such as SAGE or Charm and it's a high level language so it's good for producing working programs quickly. On the other hand it sucks for high performance and side channel resistant crypto implementations. So it's nice for research but not for production crypto.
Apr
10
comment Why do we encrypt-then mac but sign-then-encrypt?
We should sign followed by authenticated encryption.
Apr
8
comment Multi cipher CTR
@user1028028 Why would you want to do that? It's secure as far as I can tell if all blockciphers are secure, but it's very silly.
Apr
8
comment Convert SpookyHash to semi-secure 192bit hash
You can't really trade security against brute-force vs. performance that way. You can reduce the resistance to future cryptoanalysis for a moderate gain in performance by taking a standard crypto hash and reducing the number of rounds to slightly above the best current result.
Apr
8
comment How exactly does the OpenSSL TLS heartbeat (Heartbleed) exploit work?
While the bug is in a crypto library, it's not a cryptography problem. It's a general security issue and thus fits security.SE better.
Apr
7
comment Convert SpookyHash to semi-secure 192bit hash
Just use a proper hash instead. You don't know what you're doing, and even hashes designed by experts need a lot of review before you should use them.
Apr
7
comment Game with symmetric key
Bob can force a draw by sending the same value as Alice.
Apr
7
comment RSA: Letting $p$ and $q$ have different bit-size
This problem is pretty close to multi-prime RSA. In multi-prime RSA the factors are smaller as well, multi-prime RSA results in a performance gain using CRT, yours degrades performance.
Apr
7
comment RSA: Letting $p$ and $q$ have different bit-size
The cost of some factoring methods depends on the size of the modulus (GNFS) other methods depend on the size of the smallest prime (ECM). You need to ensure that the size of the factors is large enough so that the cost of ECM exceeds the cost of GNFS.
Apr
7
revised RSA: Letting $p$ and $q$ have different bit-size
edited tags
Apr
4
comment What are alternatives to number theory based crypto?
Are you talking about asymmetric encryption, or symmetric encryption? For symmetric operations almost nobody number theory based crypto.
Mar
31
revised How is the curve equation used in ECC?
added 4 characters in body; edited tags; edited title
Mar
30
comment Using the same private key for two ECC key pairs
For such an application any sane cryptographer would store a master-key and derive the individual keys with some kind of hash (I recommend HKDF-Expand).
Mar
30
comment Using the same private key for two ECC key pairs
Why would you want to do that? I can't think of any situation where this is useful.
Mar
30
revised Why the need to hash before signing small data?
edited tags
Mar
28
comment Why does Fortuna RNG use double SHA-256?
It's easier to fix a dubious property of a building block than it is to argue why you're absolutely sure that it's not a vulnerability. Another advantage of this approach is that it makes it easier to prove the security of a higher level construction. So even if they believe that length extensions are a problem many cryptographers prefer the safe choice of using a stronger hash.