Ethan Heilman
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 Sep27 answered Time Capsule cryptography? Sep27 suggested approved edit on How can a random salt for a hash function work in practice? Sep27 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 Sep27 suggested approved edit on Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? Sep27 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? Sep27 revised Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? typo Sep27 comment How can I prevent a 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/…). Sep27 answered How can I prevent a message replay with RSA? Sep27 comment How can I prevent a message replay with RSA? Why would including the expiration time in the message be insecure? Sep27 asked Would the ability to efficiently find Discrete Logs have any impact on the security of RSA? Sep27 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. Sep26 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. Sep26 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? Sep24 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. Sep24 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. Sep24 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. $$f(n) = e[n*4],e[n*4+1],e[n*4+2],e[n*4+3]$$ 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. Sep23 answered Is there a simple hash function that one can compute without a computer? Sep23 revised New PRG from old typo + reworded sentience Sep23 suggested approved edit on New PRG from old Sep23 comment New PRG from old What about using bar $|$ for concatenation? Is $.$ commonly used?