10,848 reputation
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bio website github.com/CodesInChaos
location Frankfurt, Germany
age
visits member for 3 years, 8 months
seen 9 hours ago

Jul
4
comment Hash Family Example
Sounds like you want a keyed hash. A common choice is HMAC-SHA-2(k, m). With SHA-3 it's even easier since it's not subject to length extensions, so SHA-3(k||m) works.
Jul
3
reviewed Approve How to find generator $g$ in a cyclic group?
Jul
3
comment Construct a random permutation from a random function?
If this is a practical problem, you should take a step back and describe your actual requirements.
Jul
3
comment Construct a random permutation from a random function?
Since a truncation of a PRF is still a PRF, you can trivially use the above construction where you truncate the PRF to N/2.
Jul
2
reviewed Approve cbc-mac tag wiki
Jul
2
reviewed Approve cbc-mac tag wiki excerpt
Jul
2
reviewed Approve cfb tag wiki excerpt
Jul
2
reviewed Edit cfb tag wiki
Jul
2
revised cfb wiki description
edited body
Jul
2
reviewed Approve ofb tag wiki
Jul
2
reviewed Approve ofb tag wiki excerpt
Jul
2
comment Using single EC cert/keying material to derive symmetric encryption key (for storage)?
Using asymmetric encryption is rather silly if the target is yourself. It's easier and stronger to use a symmetric secret for that. Can't you derive the P521 private key and the AES key from the same master key? That'd be a strong an clean solution.
Jul
2
comment ECDH VS. DH benchmarking in JAVA
BC uses affine coordinates (at least the implementation I looked at, perhaps it offers multiple), which are really slow for most curves. Optimized implementations should be 10-20 times as fast as BC.
Jul
1
comment How much stronger is RSA-2048 compared to RSA-1024?
@woliveirajr RSA-1024 is far weaker than that. AFAIK it's currently borderline feasible to break it for state level adversaries with a few billion to spend. If it's not breakable now, 10 years from now it should be.
Jul
1
comment What does NSA mean by 'Analyzable'?
The algorithms are similar to existing blockciphers, so cryptographers know how to analyze them. Being easy to analyze them is a good thing, because it becomes less likely that somebody suddenly find a new and much better attack.
Jul
1
revised RSA by hand - did I do something wrong? (c = m on encryption)
added 24 characters in body
Jul
1
reviewed Approve Seemingly simple decryption question
Jun
30
comment Block cipher with key longer than block size
Related questions AES Key Length vs Block Length and AES key/ciphertext space sizes
Jun
30
comment Block cipher with key longer than block size
This will likely be the case for some messages (even if the key is a shorter than the block size), but not for all of them. For a good block cipher for any key-pair $k_0 \neq k_1$ almost all messages will encrypt differently.
Jun
30
comment Why use variable p, q, g for Diffie-Hellman?
@RickyDemer Hm? Standard groups are random Schnorr groups. The only difference is that they're used by many people.