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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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May
25
comment Is Base64(SHA1(GUID)) still unique like the original GUID?
The length of a GUID is 16 bytes. You can encode these bytes as a 32 byte hex string.
May
25
comment How random are commercial TRNGS
There is one important pitfall about "injecting 160 bits is enough". You need to inject them all at once, without the attacker being able to observe the output of the PRNG in between.
May
25
comment How random are commercial TRNGS
@user1028028 Why does it matter if a PRNG is periodic? The universe will be barren and cold long before any computer finishes a whole period.
May
24
comment What is the fastest elliptic curve operation f(P) in affine coordinates such that f^n(P)=P only if n is large?
Can you describe what problem you actually want to solve?
May
22
reviewed Approve suggested edit on srp tag wiki
May
22
reviewed Approve suggested edit on srp tag wiki excerpt
May
22
comment How much data can I encrypt with AES before I need to change the key in CBC mode?
Another part of risk management is assessing how big the damage is. For an IV collision with AES-CBC it's typically not very big.
May
20
comment Is Wikipedia's table about SHA-2 collisions correct?
The :24 is probably referring to a version reduced to 24 rounds.
May
15
comment calculating beta for elgamal elliptic curves
I'd use an existing ECC library which offers a scalar multiplication function. But if you implement it yourself you can look at the Explicit-Formulas Database which as addition/doubling formulas for many curve forms.
May
15
comment calculating beta for elgamal elliptic curves
@BobbDizzles You need to look up the point addition and doubling formulas for your curve form.
May
15
comment Generating IV in TLS 1.2
RNGCryptoServiceProvider isn't that slow. It just has a large per-call overhead, so you need to ask for a few kilobytes in a single call. On my notebook it can generate around 4 million IVs (with 16 bytes each) per second on a single core.
May
12
comment Designing a security system from scratch with a custom protocol, suggestions needed
1) Cryptography is all about leaving things to chance, just with really small chances. 2) Adding a MAC is essential. HMAC in a encrypt-then-mac contruction is one good solution, dedicated authenticated encryption like AES-GCM another.
May
11
comment Does SRP reduce to DH key echange when shared password is not secret?
And you don't just need a BigInt library for SRP. If you go that way you will most likely be vulnerable to timing attacks. You need a specialized library that does exponentiation in constant time to do DH or SRP.
May
11
comment Does SRP reduce to DH key echange when shared password is not secret?
Since SRP uses DH as a building block, you need a DH implementation anyways.
May
10
comment Finding hash almost-collisions
I don't get how you go from $2^{52}$ to $2^{26}$, considering this is a near pre-image, not a near collision.
May
10
comment Finding hash almost-collisions
Your math can't be right, $2^{26}$ is far too low to win such a competition. That's less than a CPU minute on a single core. I'd expect them to easily exceed $2^{40}$. I wouldn't be surprised if they managed $2^{51}$ operations with ATI GPUs.
May
10
comment Security of Salsa20 with some known plaintext?
@davidkomer It's essential to use a distinct nonce for every message you encrypt. If you do that, Salsa20 is pretty secure. You should also consider adding authentication, so active attacks are rejected.
May
10
comment Security of Salsa20 with some known plaintext?
@D.W. Salsa20 is a stream cipher. It always uses something similar to CTR mode.
May
9
comment Recommended way of adding a pepper/secret key to password before hashing?
I would encrypt the hash
May
9
reviewed Edit suggested edit on encrypt message with one digest 0-9 instead of 01-26