John Gietzen

325 reputation

211

bio	website	twitter.com/otac0n
	location	Seattle, WA
	age	27
visits	member for	1 year, 10 months
	seen	Dec 21 '12 at 18:43
stats	profile views	30

I'm a father, a lover, a programmer and a guitarist.
Twitter: http://twitter.com/otac0n

Stack Overflow

	325 reputation	bio	website	twitter.com/otac0n	visits	member for	1 year, 10 months
211 badges		location	Seattle, WA		seen	Dec 21 '12 at 18:43

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Apr 16	awarded	Taxonomist
Feb 11	awarded	Popular Question
Aug 14	awarded	Nice Question
Jul 12	awarded	Yearling
Jun 21	awarded	Nice Question
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	awarded	Commentator
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.
Nov 12	accepted	What is pre-image resistance, and how can the lack thereof be exploited?
Nov 12	asked	What is pre-image resistance, and how can the lack thereof be exploited?
Oct 20	comment	Is there a secure cryptosystem that can be performed mentally? @TJ, I meant the content of the message.
Sep 29	accepted	Is there a secure cryptosystem that can be performed mentally?
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 @Paŭlo 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.
Sep 28	asked	Is there a secure cryptosystem that can be performed mentally?
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.