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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.


Oct
16
revised RSA Proof - di-mgt - modulo properties
fixed typo in formula
Oct
14
comment Encoding numbers that can be decoded mentally?
@RichieFrame Good luck converting to hexadecimal mentally.. you might as well use the substitution cipher directly on the decimal digits. Test: how advanced are the adversary's capabilities? Have you got a concrete threat model to go on? If you're talking about a random person seeing some numbers and trying to make sense of them on the fly, this is where security through obscurity might be more cost-effective (e.g. interleave the digits, then increment each digit by a constant you remember, modulo 10, etc..). But for anything more permanent you'll need something better.
Oct
7
comment How do we prove that AES, DES etc. are secure?
The first sentence is problematic, Luby-Rackoff is a block cipher construction proven computationally secure under certain assumptions, but it doesn't have a key as long as the message. I think you went to say something else and forgot to update the sentence.
Oct
3
comment Can an RSA private key have several public keys?
Plus, if you do that and someone gets hold of two public keys, he can take the difference and get hold of a multiple of $\varphi{(N)}$, and, well, game over.
Oct
2
comment NIST temporarily closed — will that have a negative impact on the future of cryptography?
I would be worried if it had shut down permanently, but given that it will likely reopen in less than a month, I don't think there is much to worry about. But I would be interested in reading different perspectives on the matter.
Sep
25
comment Algorithm for sharing secret information with redundant keys
This scheme is called, surprisingly enough, "secret sharing". Have you tried googling "secret sharing software"? I am getting at least 4 promising hits on the first page, have you explored these? Also, software requests are off-topic on this site.
Sep
24
comment How broken is a xor of two LCGs?
@RobinHouston Alas, the difficulty of the cryptanalysis doesn't increase proportional to the complexity of the cipher. Thanks for the edit - if noboby has produced a break before the weekend I'll give it a try (not much time for crypto during the week)
Sep
24
comment How broken is a xor of two LCGs?
This will probably require some form of linear cryptanalysis to produce a state recovery attack. The high bit is biased as fgrieu notes but after some empirical research last night I did not find any trivial flaws to exploit with this modulus $p$. Barring the MSB, I am thinking a distinguisher could maybe be constructed somehow by using the lattice structure of LCG's, but this question is far from trivial.
Sep
22
reviewed Needs Improvement Relationship between Elliptic Curve Discrete Log, Integer Discrete Log, and Integer Factorization
Sep
22
reviewed Satisfactory How to supply the GCM authentication tag to the OpenSSL command line tools?
Sep
22
reviewed Satisfactory Is it theoretically possible to construct a string that contain its own hash value?
Sep
22
reviewed Satisfactory Does the GCM authentication tag need to be protected?
Sep
22
reviewed Satisfactory Generate Elliptic Curve Private Key from User Passphrase?
Sep
22
reviewed Excellent How relevant are hardware implementations of crypto algorithms?
Sep
22
reviewed Satisfactory Does there exist a two-pass AKE protocol that is secure in eCK model and also has PFS?
Sep
22
reviewed Satisfactory What to watch for with openssl generating weak keys? (low entropy)
Sep
20
comment Can I use SHA1 as license key?
(note this is why most hardcore modern DRM is done through user accounts and remote validation and, for ultimate control, remote content distribution)
Sep
20
comment Can I use SHA1 as license key?
It's usually even simpler: most "stand-alone software" validation can be defeated by simply hooking into whatever code does the key validation, and replacing it by "this key is valid" (regardless of the key, of course). Unless said key is going to be used at some subsequent point in the program (e.g. as some authentication token for interaction with some remote server), that's it - you've "cracked" the software product, without even caring what validation mechanism was involved. I think you need to detail your specific requirements a bit more.
Sep
18
comment How to choose keys for a block cipher?
The keys $k$, $l$, etc.. are just variables. You can put whatever key you want in there (as long as it is 56 bits long, or 128 bits long, or whatever the key length for the given cipher is) and you will get one of the possible permutations of the cipher (parameterized by the key). Are you asking how those keys are generated e.g. how they are derived from passwords for instance and so on?
Sep
12
comment Break a simple compression function of a cryptographic hash function
Agreed on the second paragraph, but regarding the first paragraph, I think the point was to use some form of cryptanalysis to defeat this particular hash function, and not just invoke a generic attack. But yeah, no effort shown at all.