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I am an undergraduate computer science and mathematics student in New Zealand. My fields of interest are computer graphics, in particular the physics of light transport, and to some extent cryptography, as well as programming and software development in general.


Jan
24
comment In the Paillier cryptosystem, is there a method to judge whether an encrypted number is less than 0 (without the private key)
@phan I don't know of any additively homomorphic symmetric ciphers, but if such a cipher existed, it would not be IND-CPA secure. The attacker could use the order property to work out which of the two ciphertexts belongs to any one plaintext.
Jan
24
revised Why does Rijndael with a 256-bit block require the bottom two rows to be shifted one more space than usual?
edited title
Jan
23
comment Initialize a PRNG with a password
It's funny but those password "strength" requirements you quoted, then struck out, are actually not doing much for the password's strength. The average user (who probably reuses his weak password everywhere) will most likely get frustrated and append a symbolic "#" at the end of his password just to get it accepted by your system, and will then proceed to write it down in some file just to remember it's a different one.
Jan
23
comment Hashing a password with the password?
I understood it as HMAC(password, password) or something like that, but you are right. Plus it doesn't really have any functional advantage over just hashing the password, and may in fact be weaker due to over-engineering.
Jan
23
comment In the Paillier cryptosystem, is there a method to judge whether an encrypted number is less than 0 (without the private key)
A fully order-preserving cryptosystem would have a few issues..
Jan
23
awarded  Necromancer
Jan
22
comment How compared encryption algorithm in terms of efficiency
@almodawan No need to shout, it's an acronym.
Jan
22
reviewed Approve suggested edit on SHA-256 and AES-128
Jan
22
comment Two files encrypted with related data versus one file
Indeed, it is IND-CPA secure - I just wanted to clarify that point.
Jan
22
comment Two files encrypted with related data versus one file
"AES" is certainly not IND-CPA secure. A probabilistic encryption scheme such as CBC, CTR, OFB, .. is.
Jan
22
comment How compared encryption algorithm in terms of efficiency
No, there isn't. Big-O complexity is asymptotic - in addition to being an average - and is generally not accurate for realistic key sizes. In addition, some theoretically fast algorithms are terribly slow because they are not amenable to an efficient implementation, etc.. your best bet is to measure it, IMHO.
Jan
21
revised Using CBC with a fixed IV and a random first plaintext block
added 84 characters in body
Jan
21
reviewed Approve suggested edit on ANSI X9.31 standards for generating random numbers
Jan
21
reviewed Leave Open Finding a collision for a hash function
Jan
20
revised Do Quantum Key Distribution and Physical Unclonable Functions combine, and how?
edited tags
Jan
20
revised How does this Cesar Cipher work?
improved algorithms
Jan
20
revised How does this Cesar Cipher work?
added 151 characters in body
Jan
20
answered How does this Cesar Cipher work?
Jan
19
revised Is it safe to use RSA as a proof-of-work system?
deleted 465 characters in body
Jan
19
comment Is it safe to use RSA as a proof-of-work system?
re: last edit, in fact I suspect the client can compute the proof asymptotically just as fast as the server can as $k$ increases, making the scheme useless. I will update my answer as well as it is now misleading.