Ethan Heilman

959 reputation

416

bio	website	ethanheilman.tumblr.com
	location	Cambridge, MA
	age	30
visits	member for	1 year, 10 months
	seen	Apr 22 at 21:43
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Security Hobbyist

Github: Ethan Heilman
Twitter: Ethan Heilman

Play FlipIt:

http://ethanheilman.github.com/flipIt/playable_with_instructions.html

Blog entries:

	959 reputation	bio	website	ethanheilman.tumblr.com	visits	member for	1 year, 10 months
416 badges		location	Cambridge, MA		seen	Apr 22 at 21:43

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Sep 28	accepted	Would the ability to efficiently find Discrete Logs have any impact on the security of RSA?
Sep 27	revised	How can a random salt for a hash function work in practice? Added line breaks and rewrote some sentiences for clarity.
Sep 27	revised	What are the benefits of the two permutation tables in DES? grammar retagging
Sep 27	suggested	suggested edit on What are the benefits of the two permutation tables in DES?
Sep 27	answered	Time Capsule cryptography?
Sep 27	suggested	suggested edit on How can a random salt for a hash function work in practice?
Sep 27	revised	Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? Added spaces, list for readability, used tex notation
Sep 27	suggested	suggested edit on Would the ability to efficiently find Discrete Logs have any impact on the security of RSA?
Sep 27	comment	Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? Can you find a citation that states that it is an open question if a break in DH would have implications for RSA?
Sep 27	revised	Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? typo
Sep 27	comment	Preventing message replay with RSA @ChrisSmith Good point! We have three options: (1) as you pointed out storing the previous nonces works, (2). the first time a connection happens the nonce is generated and sent, each subsequent connection the nonce is incremented by 1 (since the attacker doesn't know the value of the nonce the attacker can't predict the new value of the nonce). (3). nonces passed between both parties and combined to generate new nonces (similar to the way syn cookies work en.wikipedia.org/wiki/…).
Sep 27	answered	Preventing message replay with RSA
Sep 27	comment	Preventing message replay with RSA Why would including the expiration time in the message be insecure?
Sep 27	asked	Would the ability to efficiently find Discrete Logs have any impact on the security of RSA?
Sep 27	comment	Is Diffie-Hellman mathematically the same as RSA? I think I might be wrong, but I thought I've heard the claim that breaking discrete log breaks/threatens RSA as well. Maybe this should be a question.
Sep 26	comment	What is the best method to determine the language used in a monoalphabetic substitution cipher? @128 - absence of whitespace is typical, most classical ciphers assume you remove whitespace. Solving classical ciphers can get a bit tricky, if you are really interested I'd recommend: 'Cryptanalysis: a study of ciphers and their solution' ( books.google.com/books/about/Cryptanalysis.html?id=fKNB-7y_Hs4C ). Also 'The American Black Chamber' (amazon.com/American-Black-Chamber-Cryptographic/dp/0894121545) has a bit of advice, examples on solving classical ciphers.
Sep 26	comment	What is the best method to determine the language used in a monoalphabetic substitution cipher? Certainly you can use a monogram frequency chart to guess the language. Another idea would be to use a common word such as in german 'ein' and look for three letters that have the same distance from each other (assuming it is a shift cipher). Where did you get a ciphertext in which you know so little about it, yet you know that it is monoalphabetic?
Sep 24	comment	Is there a simple hash function that one can compute without a computer? @FUZxxl - I think it might be safe enough for class. Not sure how safe it is generally. It would make an interesting crypto question.
Sep 24	comment	Is there a simple hash function that one can compute without a computer? Yes, RO schemes typically require a trusted third party to keep the table of inputs and outputs and to generate new outputs.
Sep 24	comment	Is there a simple hash function that one can compute without a computer? What about a function, $f$, that given a number $n$, indexes e with $n \times 4$ and returns the next 4 digits of e. $$f(n) = e[n4],e[n4+1],e[n4+2],e[n4+3]$$ So $f(0)$ would return $2718$, f(1) would return $2818$ and so on. Or use a normal number instead of e ( en.wikipedia.org/wiki/Normal_number) is you want to be more formal.