Reputation
3,637
Top tag
Next privilege 5,000 Rep.
Approve tag wiki edits
Badges
8 23
Newest
 Nice Answer
Impact
~82k people reached

Oct
1
comment What algorithm could/should be used to encrypt files for storage on untrusted servers?
Unless you at least know the information necessary to make a decision like that, you should hire someone to help you make that decision. From the way this question is asked, we can't even tell the most basic things about the type of encryption you need.
Sep
1
comment verify contents, but not order
The problem is underspecified, but as asked, I'd answer this: Use an encryption scheme that maps each card to a number from 1 to 52. Ensure that all numbers from 1 to 52 are present, each once. Since you can't decrypt any of them, you have no idea what their order is. But since each of the 52 ciphertexts appears once, each of the 52 plaintexts must too.
Aug
30
comment Proof of work for standard computers
@CodesInChaos: If a computer with a billion cores solved it a billion times faster, that would give no advantage for the specialized hardware. You could just as well use a billion regular cores. (For algorithms like SHA256, a specialized computer with 200 cores can be millions of times faster than a general purpose computer with 4 cores.)
Aug
30
comment Proof of work for standard computers
@CodesInChaos: It just needs to be about equally hard on both. Algorithms would be memory-limited, and specialized computers don't have a significant memory advantage over general-purpose computers like they do with calculations not involving tests or branches (like SHA256).
Aug
30
comment Proof of work for standard computers
@CodesInChaos: The worse it works, the better. The idea is to make it hard.
Aug
29
comment Storage of Private Keys
@JordanArseno: CodeInChaos is saying that you've made the problem more difficult than it has to be by coupling a spend from the user with a transaction from their deposit account. If you uncouple those two operations, you have many more options. (However, you will lose the ability to prove you have a 100% reserve.)
Aug
27
comment Storage of Private Keys
Encrypt the private key with the user's password so that you can decrypt it with the password. The encryption with the master public key is only used if the user's password is lost.
Aug
27
comment Storage of Private Keys
No. For a spending transaction, you use the user's password to decrypt the private key. The master private key is only used if the password is lost. (This is the recovery mechanism, not the normal mechanism.)
Aug
27
answered Storage of Private Keys
Aug
24
comment What is the effect of the different AES key lengths?
@sellibitze: No, nothing wrong with it. I just point it out because many people erroneously assume that because "128-bit AES" has a 128-bit blocksize, "256-bit AES" should have a 256-bit blocksize.
Aug
23
revised What is the effect of the different AES key lengths?
added 294 characters in body; added 87 characters in body
Aug
23
answered What is the effect of the different AES key lengths?
Aug
13
awarded  Yearling
Aug
10
comment Entropy of system data - use all and hash, or trim least significant bits?
Your approach is overly-complex and arbitrary. There are well-understood ways to do this whose behavior is known and understood. XORing is much worse than hashing because hashing concentrates entropy while XORing can destroy it. A sensible entropy pool design makes the collection problem almost trivial, and no matter how good your collector is, a bad pool will still produce crappy output.
Aug
10
comment Design question for a service that signs messages on behalf of a user
What's the problem with getting a pure JavaScript way of decrypting/signing on the client side? (Punch things like 'JavaScript RSA' into your favorite search engine and you'll find dozens of implementations.) Make sure to serve the JS over SSL, of course.
Aug
9
answered Design question for a service that signs messages on behalf of a user
Aug
9
answered Cryptographic GUID?
Aug
9
comment Approach towards anonymous e-voting
What do you mean by correctness? What would an incorrect ballot be?
Aug
8
answered Approach towards anonymous e-voting
Jul
29
comment Why does ROT13 provide no cryptographic security?
@ExplosionPills: What could they possibly do wrong? How could they possibly fail?