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Developer at Woot.com
Twitter: http://twitter.com/otac0n

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Project Euler


Jan
20
comment A simple block cipher based on the SHA-256 hash function
This is almost the exact same algorithm as listed on this question: crypto.stackexchange.com/questions/48/… The answers there also provide some pretty good insight.
Dec
5
comment Reverse engineering a hash?
This is technically off topic, based on question #3 in the FAQ. But... we can have fun every once in a while, right?
Nov
25
comment Is a book cipher provably secure?
Right, I would say that the main difference between this and a one-time pad is that: a one time pad's security is based on all possible pads that could be created, whereas a book cipher's security is based on all possible books that have been created.
Oct
20
comment Is there a secure cryptosystem that can be performed mentally?
@TJ, I meant the content of the message.
Sep
29
comment Is there a secure cryptosystem that can be performed mentally?
@IlmariKaronen, I would allow pen and paper as long as the side channel attacks could be rather easily mitigated. That is, once you are done with your encryption, you should be able to destroy the internal state of the cypher.
Sep
29
comment Is there a secure cryptosystem that can be performed mentally?
This is along the lines of what I was looking for, but as @PaĆ­lo points out, I'm looking for a key-based system.
Sep
29
comment Is there a secure cryptosystem that can be performed mentally?
This is interesting, but not particularly secure, because simple frequency analysis could discover the message fairly easily.
Sep
29
comment Is there a secure cryptosystem that can be performed mentally?
Ah, Pontifex is exactly the kind of thing I was looking for.
Sep
29
comment Is there a secure cryptosystem that can be performed mentally?
What I mean is, if you were in duress and needed to communicate without your message being discovered. This would include being captured by a small faction, while still being able to leave coded messages, etc.
Aug
2
comment Properties of PRNG / Hashes
Well, some PRNGs are unacceptable for cryptography, regardless of the seed. I made this distinction to show that it is not sufficient to simply increase the period in order to make it secure.
Jul
13
comment Is it feasible to build a stream cipher from a cryptographic hash function?
Also, I'm putting the H(plaintext) at the beginning so that it can all stream, and so that we can confirm the decrypted message.