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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years
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May
14
comment ECDSA vs RSA: Performance on Android platform and surprising results
@user13397 My point is that the main reason for ECDSA being slow in your test is not that it's implemented in pure java, it's because the implementation has not been optimized. Native code usually results in a speedup, but a smaller one. I'd guess a good java implementation would be 50 times faster than your code and native code would result in a factor 2-3 speedup beyond the best possible java implementation. But I don't have java/android experience, so these are very rough guesses coming from my experience with writing crypto code in C#.
May
13
comment ECDSA vs RSA: Performance on Android platform and surprising results
@mikeazo It uses its own BigInteger library. But even with pure java code you can get much better performance.
May
13
revised ECDSA vs RSA: Performance on Android platform and surprising results
added 351 characters in body
May
13
answered ECDSA vs RSA: Performance on Android platform and surprising results
May
11
comment How to decrypt a text which is ciphered same length key?
See also: How does one attack a two-time pad (i.e. one time pad with key reuse)?
May
9
comment Point addition and doubling in Ed25519 (ref10)?
sc_clamp makes no sense on encoded points. It operations on scalars.
May
9
comment Why is Triple DES not vulnerable to meet in the middle attacks?
Very similar to the question Why is triple-DES using three different keys vulnerable to a meet-in-the-middle-attack?
May
9
comment Point addition and doubling in Ed25519 (ref10)?
Is your code publicly available?
May
9
comment Point addition and doubling in Ed25519 (ref10)?
If you only need one coordinate of the output, you can convert to montgomery form, compute the scalar multiplication and convert back. You only need your approach if you need both coordinates.
May
9
revised Point addition and doubling in Ed25519 (ref10)?
added 27 characters in body
May
9
comment Point addition and doubling in Ed25519 (ref10)?
Why do you want to avoid the conversion to Montgomery for DH? It's a bit slower than using (Y/Z) coordinates in Edwards form due to an additional field inversion, but almost certainly faster than what you're attempting to build. Conversion back to edwards at the end of the scalar multiplication is free, but I didn't do so for compatibility with existing Curve25519 shared secrets.
May
9
answered Point addition and doubling in Ed25519 (ref10)?
May
8
comment Decrypt a public encrypted message and Sign a signature, how the math is different?
With RSA you generally use different padding. With other schemes encryption and signing usually have very little in common.
May
7
awarded  Enlightened
May
7
awarded  Nice Answer
May
7
revised Cryptodefense ransom use RSA-2048. Any chance with known plaintext attack?
deleted 29 characters in body
May
7
comment Cryptodefense ransom use RSA-2048. Any chance with known plaintext attack?
You have no chance if the malware has been implemented properly.
May
7
comment ECC partially blind signature scheme verification
I'd consider using RSA based blind signatures. It's simple, robust and supports tons of additional features. The main downsides are the lower performance and larger signatures.
May
7
revised Can Skein be used as a secure MAC in format H(k || m)?
added 8 characters in body
May
6
comment Is knowing the private key of RSA equivalent to the factorization of $N$?
If you know $e$, $d$ and $n$, you can efficiently factor $n$. Just knowing $d$ is not enough if $e$ is big.