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12041
bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 2 years, 9 months
seen 2 days ago

Feb
5
comment Is such a crypto-system available?
Doesn't work. 1) k_new would be an encryption key, not a decryption key 2) f is invertable. So you can calculate k1 = k_new/k2.
Feb
5
reviewed Approve suggested edit on Commutativity of keyed hashes
Feb
5
comment How to check the strength of an encryption algorithm?
By primitive I mean a pseudo-random-permutation(aka blockcipher) like AES, an unkeyed permutation like what keccak uses at its core etc. or even a complete hashfunction or MAC. Where the new algorithm can be something like a new chaining mode.
Feb
5
comment How to check the strength of an encryption algorithm?
@Mok-KongShen Depends on what kind of "encryption algorithm" he's talking about. If he invented an AES alternative(i.e. a symmetric primitive), reviewing that will be off-topic. If he wants to know if using existing primitives in a certain way is secure, that can be on-topic (depending on how its asked).
Feb
5
comment How to check the strength of an encryption algorithm?
Are you talking about an actual primitive you invented(AES is for wusses, use Samuel's super secure cipher), or are you talking about the way your application uses standard algorithms to encrypt data?
Feb
5
comment How to check the strength of an encryption algorithm?
By having several competent people review it.
Feb
4
comment Why does the recommended key size between symmetric and assymetric encryption differ greatly?
Not every asymmetric system needs those huge keys. Elliptic curves for example only need a key twice as large as those used for symmetric crypto.
Feb
4
comment Source for examples with broken cryptography
Concerning primitives, the SHA-3 candidates that didn't make round 2 are a nice list: ehash.iaik.tugraz.at/wiki/The_SHA-3_Zoo
Feb
4
comment Is there a problem with constructing a CSPRNG using MD5 or SHA1?
The CRC like function for mixing gives me a bad feeling, but without details its hard to say anything concrete. The MD5 for output is rather harmless, but quite inefficient (MD5 is four times as fast for input than for output)
Feb
4
comment Is there a problem with constructing a CSPRNG using MD5 or SHA1?
How do you want to use these? For mixing randomness into the pool(efficiency isn't that important there) or for generating the output stream (you can use AES-CTR for that)
Feb
4
comment Crypto puzzle as proof of randomness?
You can use the same technique with other elliptic curves, or even finite fields. For example Bitcoin Vanitygen uses it so that the party who uses a lot of computational power to find the meaningful address doesn't need to know the private key.
Feb
4
comment ECDH VS. DH benchmarking in JAVA
You could compare with BouncyCastle's performance.
Feb
3
comment Why do the elliptic curves recommended by NIST use 521 bits rather than 512?
I guess $2^{521}-1$ being prime was too nice to pass up.
Feb
3
comment Crypto puzzle as proof of randomness?
summing A would be called a group addition, summing s a scalar addition.
Feb
3
revised Crypto puzzle as proof of randomness?
added 298 characters in body
Feb
3
comment Crypto puzzle as proof of randomness?
But a DHT usually has no authoritative server, so who would enforce the time limit or generate the nonce?
Feb
3
revised Crypto puzzle as proof of randomness?
added 91 characters in body
Feb
3
comment Crypto puzzle as proof of randomness?
"being able to influence it more than a few bits is a security risk" seems like a really weird requirement.
Feb
3
answered Crypto puzzle as proof of randomness?
Feb
3
comment Security of .net AES implementation and security of a hash MAC
Your question is pretty vague. What kind of weakness in .net's AES are you looking for? Timing attacks? I wouldn't worry too much about problems with .net's library itself, but rather about your code using it. The bad API makes it hard to write secure encryption in .net. Your second question is even more vague, you didn't really describe your scheme. But it's probably not secure. There are several related questions, such as "Non-cryptographic hash function as MAC for stream ciphers".