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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.


Dec
27
comment Time Capsule cryptography?
@IanBoyd The puzzle can be efficiently created. It's solving it that's difficult.
Dec
25
comment Can a nested block cipher avoid the meet in the middle attack by using a secret initialization vector for the inner encryption?
The IV is meant to be public.
Dec
23
awarded  Talkative
Dec
21
awarded  Nice Answer
Dec
21
comment True 128bit secured password length?
16 character password $\neq$ 128 bits of entropy. To fix it, either add more characters to your password, or use a slow KDF (key derivation function) to add some more bits of security to your key in the form of computational cost, see PBKDF2, bcrypt, scrypt, ... you can probably get an extra 24 bits at most before this becomes inconvenient to the user.
Dec
21
comment Why is asymmetric cryptography bad for huge data?
No, the ratio is fine, but I was just noting that the speeds you quoted are generally only obtained when you hardcode everything in a very tight loop, with zero function calls or parameters, in assembly. In any realistic application this is simply not logistically viable - you need the code to be modular and flexible so that it can be reused easily. OpenSSL uses a decently optimized AES-NI implementation and AES-128-CBC runs at 720MB/s per core on my overclocked i5 (openssl speed -evp aes-128-cbc).
Dec
21
comment Why is it important that phi(n) is kept a secret, in RSA?
@PaŭloEbermann That is true, and the reason this answer is meant to be complimentary to CodesInChaos's one (expanding on his second point). That said, $n$ might be used in multiple cryptographic primitives (not just RSA) in any given protocol, so assuming you know $\varphi{(n)}$ (which in itself is rather contrived) you will want to get $p$ and $q$ to help attack those parts of the protocol as well, depending on what your goals as an attacker are.
Dec
20
comment Is there a field guide to ECC for the IT Security layman?
Perhaps more importantly, it also helps you identify and steer clear of snake oil..
Dec
20
comment Is there a field guide to ECC for the IT Security layman?
This applies to high-level protocols, of course - implementing your own cipher is almost always a terrible idea because that actually requires years of training and analysis, whereas by just putting together cryptographic constructions you are using existing primitives which are assumed to have specific properties, which you can use to prove your construction is secure assuming the underlying primitives are (which is more reasonable).
Dec
20
comment Is there a field guide to ECC for the IT Security layman?
I disagree about your comment - while a certain amount of standard, general-purpose schemes already exist for most situations, it is sometimes necessary to roll your own cryptographic protocol for your particular use-case. Knowing the difference between a HMAC and a KDF, what IND-CCA means and what a birthday attack is, is crucial to get it right, or at least not fail as much. Seriously, someone has to implement all of this at the end of the day, and if you have the skills, why the hell wouldn't you apply them? Security professionals are not superior beings, they are humans like you and I.
Dec
20
answered Why is it important that phi(n) is kept a secret, in RSA?
Dec
20
reviewed Edit suggested edit on Why is it important that phi(n) is kept a secret, in RSA?
Dec
20
revised Why is it important that phi(n) is kept a secret, in RSA?
added site tags
Dec
20
comment Why is asymmetric cryptography bad for huge data?
Sorry but those AES-NI numbers are ludicrous and are heavily artificial. The latest processors can get a per-core throughput of 800-900MB/s at best in a real implementation with a proper mode of operation. Your point still stands but remember marketing benchmarks are not representative of real life performance.
Dec
19
revised AES vs Blowfish taking key-length into account
added 168 characters in body
Dec
19
comment AES vs Blowfish taking key-length into account
@AlexandreYamajako That is quite true and a fair point that I hesitated to put in my answer, Blowfish has not received nearly the same amount of cryptanalytic attention as AES. I will add it now.
Dec
19
answered AES vs Blowfish taking key-length into account
Dec
18
comment Attacks on the RSA Cryptosystem
en.wikipedia.org/wiki/Coppersmith's_Attack
Dec
18
comment Attacks on the RSA Cryptosystem
This doesn't answer the question. There is, in fact, a specialized attack which allows one to factor N faster than testing all the missing bits when you have enough bits of $p$.
Dec
17
revised Can the encryption exponent e be greater than ϕ(N)?
deleted 1 characters in body