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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 2 years, 9 months
seen 2 days ago

Jul
30
answered Why do we need extra hashing if we could use simpler scheme?
Jul
30
comment Purpose of outer key in HMAC
The strange part for me is that HMAC requires this key, but SHA-3 candidates used as MAC don't. I believe Skein has a security proof for a mode that's similar to H(k||m). "We prove that if Threefish is a tweakable PRP (pseudorandom permutation) then Skein is a PRF."
Jul
29
comment Why does ROT13 provide no cryptographic security?
Caesar is a block cipher in ECB mode using 4.7 bit keys&blocks :P
Jul
29
comment What is the name of this kind of protocol
Looks related to en.wikipedia.org/wiki/Three-pass_protocol which is insecure for xor, but works for some other commutative ciphers.
Jul
29
comment Can I jettison MAC if I already have SHA1(M)?
Your alternate protocol seems a bit underspecified. Are you still using a TLS handshake? Does Bobs response only consist of M? What padding do you use? Is the message split in several blocks, or just a single continuous stream with an IV at the beginning, and the padding in the end? Do you send multiple messages through the same channel?
Jul
29
comment Can I jettison MAC if I already have SHA1(M)?
I believe those attacks can be avoided if you're really careful in the implementation. But I'd avoid such a scheme because they're so hard to get right, while offering no real advantage over modes which do not suffer from these issues.
Jul
29
comment Can I jettison MAC if I already have SHA1(M)?
If you want to go this route, I'd use an encryption mode that's immune to padding oracles. With your current choice it's far too easy to make a subtle mistake that compromizes confidentiality.
Jul
29
comment Can I jettison MAC if I already have SHA1(M)?
I don't agree with your short answer. It's secure if implemented correctly. But with this combination of encryption and authentication it's very easy to make an implementation mistake.
Jul
28
comment What would be the most effective way to brute force a 16 char AES key?
Putting a password directly into an AES key for encryption is just as stupid as using the same scheme instead of standard password hashing.
Jul
28
comment Why does ROT13 provide no cryptographic security?
It has a keysize of 0. en.wikipedia.org/wiki/Kerckhoffs's_principle
Jul
28
comment Is modern encryption needlessly complicated?
A lot of modern crypto is unnecessarily complicated. X509, TLS,...
Jul
28
revised Is there some way to generate a non-predictable random number in a decentralised network?
edited tags
Jul
28
revised Advantages of each encryption mode
added 15 characters in body; edited tags
Jul
28
revised Cipher Feedback Mode
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Jul
28
revised Can a “pattern” in a series of passwords be detected from their hashes (and maybe a single raw password)?
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Jul
27
awarded  Quorum
Jul
27
comment Adaptive Hash Functions: How to tell how many iterations were used?
I still think this fits security.SE better than crypto.SE.
Jul
27
answered Adaptive Hash Functions: How to tell how many iterations were used?
Jul
27
revised Diffie hellman key exchange on elliptic curve over an extension field
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Jul
27
revised Elliptic curve cryptography related key attacks
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