9,824 reputation
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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 3 months
seen 11 hours ago

Nov
2
comment RSA 896 vs 1024 vs 2048 in Javascript?
Since SSL already blocks most attacks, the gain by using JS crypto on top of that can only be meaningful with keys that even a powerful attacker can't break. At minimum 2048 bit RSA or 224 bit ECC.
Nov
1
reviewed Reject suggested edit on Why does WPA-PSK not use Diffie-Hellman key exchange?
Nov
1
comment How to Distribute the Shares using Secret Sharing for arbitrary Monotone Access Structures
@DrLecter I'm not sure if your edit made the question requirements stricter. The OP might be happy with different weights for each secret holder without being handle the general case.
Nov
1
comment Does ssl_rsa_with_rc4_128_md5 have known weaknesses?
For online banking you only face ordinary criminals and long term security isn't essential either. So this should be fine. But I wouldn't be comfortable with it when security requirements are high. Long term RSA key used for confidentiality => no forward secrecy, possibly too small RSA key and RC4 has known biases.
Nov
1
reviewed Approve suggested edit on What is the recommended replacement for MD5?
Oct
31
revised How to calculate entropy of a combined key
added 39 characters in body
Oct
31
reviewed Approve suggested edit on monotone-access-structure tag wiki excerpt
Oct
31
answered How to calculate entropy of a combined key
Oct
31
reviewed Approve suggested edit on How to calculate entropy of a combined key
Oct
31
reviewed Approve suggested edit on How are IVs used in association with RSA Encryption?
Oct
31
comment How are IVs used in association with RSA Encryption?
What's funny about using random padding is that we usually encrypt random symmetric keys (as part of hybrid encryption), a scenario where randomness isn't actually required.
Oct
31
reviewed Approve suggested edit on If I have the unencrypted text and the encrypted text, can I calculate the key?
Oct
31
comment If I have the unencrypted text and the encrypted text, can I calculate the key?
This is a "known plaintext attack" and if you use a modern algorithm properly you'll be immune to it.
Oct
31
comment How to develop a public key cryptosystem based on a hard problem?
@DrLecter I didn't say that you need that specific property. But that you need a non trivial mathematical property beyond one-way-ness. Commutativity is one example, many other schemes rely on a trapdoor. The chance that an arbitrary hard to invert function has such a property is very small.
Oct
30
reviewed Approve suggested edit on Are there any differences in operation between existing Diffie-Hellman specifications?
Oct
30
comment How to develop a public key cryptosystem based on a hard problem?
We know many many hard to invert functions, but only a handful of fundamentally different asymmetric encryption/key-exchange schemes.
Oct
30
comment How to develop a public key cryptosystem based on a hard problem?
For asymmetric encryption or key-exchange your system needs lots of mathematical structure. Almost all one-way functions are not suitable. For example with diffie-hellman key-exchange you not only need the property that $A=G^a \mod p$ is hard to invert, you also have the property that $A^b=(G^a)^b = G^{ab} = (G^b)^a = B^a$ i.e. you are able to compute the same shared secret using $A$ and $b$ or $B$ and $a$. Where lowercase letters are private keys and upper case letters the corresponding public keys.
Oct
30
comment How to develop a public key cryptosystem based on a hard problem?
You only described a one-way function so far, something similar to a hash function. You didn't say where the asymmetric component comes in.
Oct
30
reviewed Approve suggested edit on Why does the new encryption scheme proposed by authors stop an adversary from guessing the subspace of the secret key?
Oct
30
comment How does the IV or initial counter increase internally for each block in AES CTR mode?
There isn't really a one true CTR mode. There are many different variants of CTR mode which differ by how they compute the per-block input from IV and counter.