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May
11
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May
10
revised Reciprocal block ciphers
added 21 characters in body
May
10
comment Reciprocal block ciphers
@Melab That's just silly. You can make it swap the halves after the last round without any loss to security - any attacker can trivially swap halves of the ciphertext as they please.
May
10
answered Reciprocal block ciphers
May
10
comment Reciprocal block ciphers
When you say reciprocal block cipher, do you mean that $Dk$ and $Ek$ are the same function?
May
2
comment Clefia Vs AES 128 bit
@tony9099 Sorry, all these questions can be answered by simple googling - not going to do that work for you.
May
2
answered Clefia Vs AES 128 bit
Mar
30
comment Is this a valid scheme to authenticate through a 'human-readable' certificate?
While I do not 100% agree with your notions in point #1 and #2, I did not consider the attack where Eve swaps out questions for those she knows the answer with. Do you know of any secure scheme where two human users can prove their identity to eachother through some means without having shared a cryptographical certificate/secret beforehand? Is it possible at all?
Mar
30
accepted Is this a valid scheme to authenticate through a 'human-readable' certificate?
Mar
30
comment Is this a valid scheme to authenticate through a 'human-readable' certificate?
You have no idea how much entropy there is with question/answers, it could be an arbitrary amount. Could you elaborate on your replay attack? I don't fully understand what Eve would replay, and how it would affect security.
Mar
30
comment Is there an existing authorative definition of the cryptographic term 'pepper'
@RichieFrame Forgive me, but isn't giving an advantage to systems with more cores the opposite of what you want? The less parallel an attack, the more expensive it becomes.
Mar
30
revised Is this a valid scheme to authenticate through a 'human-readable' certificate?
edited body
Mar
28
revised Is this a valid scheme to authenticate through a 'human-readable' certificate?
added 7 characters in body
Mar
27
comment Is this a valid scheme to authenticate through a 'human-readable' certificate?
@RickyDemer I clarified in the question that Eve does not know the answer to the questions at least until the long-term exchange of certificates has completed.
Mar
27
revised Is this a valid scheme to authenticate through a 'human-readable' certificate?
added 77 characters in body
Mar
27
comment Is this a valid scheme to authenticate through a 'human-readable' certificate?
@RickyDemer It is right there: "let's assume that Eve does not know the answer to the questions at the time of the exchange". This excludes being able to guess the answers in the timeframe of the exchange.
Mar
27
comment Is this a valid scheme to authenticate through a 'human-readable' certificate?
@RickyDemer Just like it's infeasible to guess the private key, I assume the questions are of sufficient quality it's infeasible to guess them, at least within the timeframe of the exchange. The questions I used as an example are weak toy questions. $H$ is a slow hash function, like scrypt.
Mar
27
comment Is this a valid scheme to authenticate through a 'human-readable' certificate?
@RickyDemer If bruteforce on the answers is the strongest attack on this scheme, that would qualify it as 'secure', wouldn't it? Your argument could also be used to say public signatures are insecure, because it allows you to check your guesses for the private key.