33,494 reputation
12872
bio website
location
age
visits member for 3 years, 5 months
seen 9 mins ago

Sep
18
reviewed Leave Closed Is appending the hash of the plaintext to the end of an encrypted message sufficient to ensure integrity?
Sep
18
reviewed No Action Needed How do institutions like banks do RSA with big primes?
Sep
18
reviewed No Action Needed VKO GOST R 34.10-2001 (described in RFC4357), Key Agreement Algorithm. Looking for its implementation/detailed description/examples
Sep
18
comment GCM: Math behind update of AAD after ciphertext has been processed
@owlstead: I don't believe that quite works (unless you know the length of the AAD beforehand). The problem is that if you've already computed $\operatorname{GHASH}_H(A_{0..x}||C)$, there's no easy way to insert $A_{(x+1)...z}$ into the middle. If that's a requirement, I would suggest you keep running $\operatorname{GHASH}_H(A_{0..x})$ and $\operatorname{GHASH}_H(C_{0..y})$, and glue them together only when you've seen the entire $A$
Sep
17
reviewed No Action Needed Finding algorithm: desire RSA's uniqueness and ECDSA's space efficiency
Sep
17
comment Encryption with data loss protection
If you want to ensure authentication, adding a hash is the wrong answer (anyone could modify your book and update the hash). Instead, I suggest you start looking at signatures; in short, you'd sign your book with your private key; someone (who gets a verified copy of your public key; the "verified" is the tricky part) can verify that the book is precisely as you signed it.
Sep
17
reviewed Close Are there cryptographic hash functions with homomorphic properties?
Sep
17
reviewed Close Is appending the hash of the plaintext to the end of an encrypted message sufficient to ensure integrity?
Sep
17
reviewed No Action Needed Understanding Pseudo Random Generators
Sep
17
comment Encryption with data loss protection
The obvious way to do this is encrypt your data normally, and then apply an unkeyed redundancy transform (such as what's in QR); that'd meet the requirements, and we don't have to worry about the redundancy aspects from causing security problems.
Sep
17
revised GCM: Math behind update of AAD after ciphertext has been processed
added 53 characters in body
Sep
17
revised GCM: Math behind update of AAD after ciphertext has been processed
deleted 3 characters in body
Sep
17
answered GCM: Math behind update of AAD after ciphertext has been processed
Sep
16
reviewed Close How Could the Music Industry Go About Implementing Crypto?
Sep
16
reviewed Close Recommended skills for a job in cryptology
Sep
12
comment Why are we advising PKI if we know that quantum computers will break them?
Why do you say that it's established fact that someone will have a quantum computer that can handle (say) 1000 qubits in 10-20 years???
Sep
11
comment stream cipher computation cost
I have no idea what would be a good answer other than "any decent symmetric cipher takes $\Theta(n)$ time to encrypt a message $n$ bits long". A decent cipher can't take less time than that (because it needs to modify at least half of the bits in the message); and since we have algorithms that take that much time, we don't really consider algorithms that take superlinear time. Of course, if your question is about the constant of proportionality (that is, the part that is hidden by the $\Theta$ notation), well, that's implementation dependent.
Sep
11
answered Regarding Key Strength with DES and Blowfish
Sep
11
reviewed Leave Open How can one generate pairs/triplets/…/n-ary MD5 collisions
Sep
11
revised AES Affine Transformation Polynom Representation
deleted 2 characters in body