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Sep
8
revised Breaking Double Encryption
edited tags
Sep
6
comment How to prove Security of Onion Layers of encryption?
Haven't read it, but this might give some clues.
Sep
5
comment Can Bitcoin HD public keys be used for symmetric encryption?
@sylarmorgan If the keys are good, publishing i shouldn't matter. It is used in generating the public key, but there is (hopefully) enough additional entropy there that it wouldn't matter. For example, if I generated keys to encrypt messages to you as Hash(really_long_shared_secret || i) and sent to you i and a message encrypted with the key, the attacker knowing i doesn't help them very much. In the encryption, there are ways we could mess up (for example, this key generation is deterministic, so we would have to use good IV's as input to the block cipher, etc).
Sep
5
revised Can Bitcoin HD public keys be used for symmetric encryption?
added 497 characters in body
Sep
5
answered Can Bitcoin HD public keys be used for symmetric encryption?
Sep
4
awarded  Yearling
Sep
4
comment Is using SHA256 to extract entropy from a p-rand nonce a good way to create keying material?
+1 Always best to stick with standards.
Sep
4
comment Is using SHA256 to extract entropy from a p-rand nonce a good way to create keying material?
Personally, I'd use HMAC-SHA256. See this paper for why and some other possible constructions to consider (especially if your processor has AES-NI).
Sep
4
comment Can Bitcoin HD public keys be used for symmetric encryption?
Let me see if I understand. You have two parties who have previously shared (part) of a wallet. You want to use that shared information to establish secure communications between the two. Is that correct?
Sep
2
comment How to make a document truly read only
And remember, this is a cryptography site so our solutions will definitely be geared towards cryptography. There could be non-cryptographic answers to the question.
Sep
2
comment How to make a document truly read only
Answer is, you probably can't. Anyways, you need to define a threat model. What do you consider a breach of "read only"? If someone memorizes the document and types it out in a new word processor document? Printing? Etc. If you can formally define what it means to be read-only, we may be able to help.
Sep
2
comment How Proof all Subgroup point of prime order elliptic curve have prime order [#G=#E]?
Given Lagrange's theorem (which will be in any decent textbook on number theory), the proof is straight forward.
Sep
2
revised How Proof all Subgroup point of prime order elliptic curve have prime order [#G=#E]?
added 1 character in body
Sep
2
comment How Proof all Subgroup point of prime order elliptic curve have prime order [#G=#E]?
Actually, there is one point for which this will not hold.
Aug
27
comment What's the point of a Meet In The Middle attack using i.e. double AES with throw-away keys?
First off, a meet in the middle attack on AES is not even computationally feasible, so an attacker wouldn't use it period.
Aug
26
awarded  Pundit
Aug
26
comment How to distribute symmetric key between $n$ entities?
Shamir secret sharing?
Aug
22
comment Is it secure to derive an AES key from a MAC?
@HannoBinder your idea is valid, but I don't necessarily think it is simpler.
Aug
22
comment Is it secure to derive an AES key from a MAC?
@Augusto are you the OP? They seem reasonable to me. In any usable system there is going to be a point where security breaks.
Aug
22
answered Is it secure to derive an AES key from a MAC?