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Aug
25
comment Is there any research about cryptography on nondeterministic Turing machines?
Here's an attack that breaks your scheme. Suppose we have 1000000 bits of known (debiased) keystream. Guess $K$. Guess a 1876000-bit sequence containing at most 690142 0's; it is a possible input to the von Neumann debiaser. Test whether applying von Neumann debiasing to this yields the known keystream; reject if not. Guess $M_i$ for each position $i$ where this sequence has a 1 bit. Test whether $H(K,N,i,M_i)=0$ for each such $i$; reject if not. If all tests pass, accept and output $K$. w.h.p, the debiaser only needed $\le 1876000$ bits of input, and at most 690142 in its input were 0's. [..]
Aug
25
answered multiple keys via HKDF - whats better, one or two applications of HKDF-extract
Aug
23
comment what is pairing in cryptography?
What reading have you done? What effort have you made? Have you looked in Wikipedia? Have you looked in modern textbooks? Have you searched via Google? Have you read course notes on the topic? We expect you to do some investigation on your own before asking here: ask only questions that you actually care about -- and if you care about it, do a little research on your own. In this case, it is very easy to find basic information on pairings (e.g., on Wikipedia).
Aug
23
revised How can I use SSL/TLS with Perfect Forward Secrecy?
added 223 characters in body
Aug
23
comment The specification of modern, non-communicating cipher machinery
These questions all seem pretty standard, for applied cryptography. Have you read Cryptography Engineering, by Ferguson, Schneier, and Kohno? Or other good textbooks on applied cryptography? They'll tell you about things like how long your IV should be, why you need a message authentication code, how to resynchronize after corruption, etc. You should start by studying what is already known about computer-based systems, then analyze for yourself how they apply to your situation, and come back if there's anything that you can't work out from the standard references.
Aug
22
comment Create a field in PBC
What you want to do has nothing to do with pairing-based cryptography. Why would you want to use PBC, or something related to pairings?
Aug
22
comment Is there any research about cryptography on nondeterministic Turing machines?
@PaŭloEbermann, thank you, yes, that's a good summary (with the caveat that you have to be able to verify whether your guess was correct or not).
Aug
22
comment Is a 1024-bit DSA key considered safe?
@bdesham, sorry, I don't know the answer to your second question. I don't know of any way to replace it without revoking it and creating a whole new key, but maybe someone else will know.
Aug
22
comment How can I accomplish Key Derivation in JavaScript?
@AbhiBeckert, If you want advice on how to get the best possible security for your web service, I recommend you ask a question that describes your web service, your security needs, your requirements, your user population, and similar information. We can't read your mind; and it's hard to provide a useful answer without that information. As it is, I can only answer the question you asked (whether it's possible to take a weak password and turn it into a strong crypto key); the answer is no, you can't. It doesn't matter how inconvenient that answer is for users; the answer remains correct.
Aug
21
reviewed Approve suggested edit on Is it possible to match encrypted documents using user-defined search terms?
Aug
21
revised Will our app be FIPS 140-2 compliant if we use our own AES algorithm implementation?
Make the title slightly clearer.
Aug
21
comment How resilient to attackers with extreme resources available is this encryption method?
@Everlag, the short answer is you can't: you need to rely upon something more than just a passphrase. The simple answer is to use public-key key exchange as others have suggested (e.g., like SSL). Or, maybe you need secure storage somewhere (where the private key can be stored securely; possibly encrypted under the passphrase); maybe you need a hardware device or token or smartcard; maybe you need something else. It's hard to tell you what the best approach will be, without knowing anything of the application requirements or restrictions or goals beyond that you want very strong cryptography.
Aug
21
comment Understanding the “cube-root math” behind an RSA signature forgery
hlh, sorry, I don't understand your question. The paper explains why the answer is $2^{1019} - (N * 2^{34}/3)$. They've already given you this answer (magically) and are now explaining how you can verify that this answer is correct. Plug in $A=2^{1019}$, $B=N*2^{34}/3$ into (7), exactly as the paper tells you do, and then simplify, and then the paper tells you why the cube of $2^{1019} - (N * 2^{34}/3)$ is $2^{3057}-N*2^{2072}+G$.
Aug
21
answered Generate Elliptic Curve Private Key from User Passphrase?
Aug
21
answered Is a 1024-bit DSA key considered safe?
Aug
21
answered Strength of CBC with Ciphertext Stealing
Aug
21
comment Strength of CBC with Ciphertext Stealing
This doesn't really answer the OP's question, which was about the degree of risk due to leaking the length. This is the one respect in which CBC-CTS does not achieve the same level of security as plain CBC, as CBC-CTS leaks more precise information about the plaintext length.
Aug
21
answered How can I accomplish Key Derivation in JavaScript?
Aug
21
answered How resilient to attackers with extreme resources available is this encryption method?
Aug
21
comment Understanding the “cube-root math” behind an RSA signature forgery
The paper explains how it got this number immediately after the expression you are quoting. See equations (7) and (8) and the surrounding text (continuing onto the top of the next page).