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Sep
3
comment One-way function and $EXP$
"even if $P=NP$ this not immediately correct that we can easily invert one way functions" - Yes it is. If $P=NP$, all one-way functions can be inverted in polynomial time. This is a simple theorem. (Remember, a one-way function must be computable in the forward direction in polynomial time. This means if you have a guess at the inverse, you can check whether your guess is correct in polynomial time. That in turn means that finding the inverse is a problem in $NP$: it's a problem whose solution can be verified in polytime, which is basically the definition of $NP$.)
Sep
3
revised Using one-way hash functions as the encryption method
added 1129 characters in body
Sep
3
answered Using one-way hash functions as the encryption method
Sep
3
comment Why the symmetric key layer in PGP?
See crypto.stackexchange.com/q/14/351 and crypto.stackexchange.com/q/586/351 and crypto.stackexchange.com/q/5782/351, which already contain answers to your question.
Sep
3
answered One-way function and $EXP$
Sep
2
comment What is the relation between hash chaining and chosen prefix attack
@user129789, it doesn't prevent collisions; it is just a strategy for dealing with collisions when building a hash table. And, the context of those lecture notes has nothing to do with cryptography, and thus nothing to do with this site.
Sep
1
comment What is the relation between hash chaining and chosen prefix attack
@user2726531, those lecture notes relate to non-cryptographic hashes. Here we are talking about cryptographic hashes. Moreover, now that I see the lecture notes, your use of the phrase "hash chaining" was ambiguous; in cryptography, the most natural interpretation of the word "chaining" is the Merkle-Damgaard construction used to build a hash function, which is apparently not what you meant. That's why I asked you to edit your question to define what you meant by hash chaining, but it seems you still haven't done that...
Sep
1
answered Storing Credentials for a Third Party
Sep
1
comment What is the relation between hash chaining and chosen prefix attack
You might want to edit the question to (1) define what you mean by hash chaining, (2) tell us what research you've done so far, and (3) where you've gotten stuck.
Sep
1
answered What is the relation between hash chaining and chosen prefix attack
Sep
1
answered How to renew keys for a statically-encrypted database
Sep
1
comment Feedback requested on a method of posting a message without revealing the author
I suggest editing your question to make clearer what the question is. It's important to have a clear, focused question, but right now the body of the question doesn't contain any questions (just statements).
Aug
30
reviewed Reject suggested edit on encoding tag wiki excerpt
Aug
30
reviewed Reject suggested edit on Why is the complexity of RSA-1024 80 bit and not 86 bit?
Aug
30
reviewed Reject suggested edit on order-preserving tag wiki excerpt
Aug
30
reviewed Reject suggested edit on order-preserving tag wiki
Aug
30
revised The security of an encrypt and MAC
deleted 50 characters in body
Aug
30
comment The security of an encrypt and MAC
@RickyDemer, you are right (on both points). I mis-read your statement. Sorry about that. Thank you for your comments.
Aug
29
comment RC4 system pitfalls
You're still missing a lot of details. Can you provide the exact algorithms? e.g., what is the HMAC computed on? (on the ciphertext/on the plaintext?) How is the HMAC key for each segment chosen: is it the same for all files and all segments, or does it vary? How is the RC4 key for each segment generated? is it a function of some master key, and if so, what's the function? Can you specify the exact DH key exchange more precisely? How is the DH exchange authenticated? There are many possible problems; your question doesn't specify enough detail to analyze the scheme at a technical level.
Aug
29
comment The security of an encrypt and MAC
@zof, a one-time pad is impractical, for all the standard reasons (use search to find more discussion of this). See also the comment by fgrieu. (Ilmari, if you are deriving per-message keys from a master key using some computationally secure method, then it is not fair to call what you've got a one-time pad any longer.)