dchest

487 reputation

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bio	website	codingrobots.com
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	age	30
visits	member for	1 year, 9 months
	seen	May 17 at 11:14
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Programmer and founder at Coding Robots

	487 reputation	bio	website	codingrobots.com	visits	member for	1 year, 9 months
310 badges		location			seen	May 17 at 11:14

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Apr 25	revised	Tamper-proofing log files Fixed link
Apr 25	suggested	suggested edit on Tamper-proofing log files
Mar 31	comment	Single-purpose symmetric encryption scheme for single files @StephenTouset no, it uses MD5. See github.com/Chronic-Dev/openssl/blob/master/apps/enc.c#L552 and openssl.org/docs/crypto/… or stackoverflow.com/questions/9488919/openssl-password-to-key. Also, the output format doesn't seem to be documented.
Mar 30	comment	Single-purpose symmetric encryption scheme for single files Have you seen the file format of scrypt utility? It's a good reference on how to do it properly: code.google.com/p/scrypt/source/browse/trunk/FORMAT
Mar 30	comment	Single-purpose symmetric encryption scheme for single files @StephenTouset proper key derivation?
Mar 13	comment	Security of tokenization of plain text conversations - cryptanalysis See also crypto.stackexchange.com/questions/3645/…
Mar 9	comment	ChaCha cipher + Poly1305 I think you're referring to hashing the result of DH. djb says you should hash the result of curve25519 scalar multiplication before using it ("Both of you can then hash this shared secret and use the result as a key for, e.g., Poly1305-AES." cr.yp.to/ecdh.html), so crypto_box uses HSalsa as a hash function for shared key. Crypto_secretbox doesn't have this step.
Mar 8	comment	ChaCha cipher + Poly1305 HSalsa is used to turn Salsa20 (8-byte nonce) into XSalsa20 (24-byte nonce) as per "Extending the Salsa20 nonce" paper: cr.yp.to/snuffle/xsalsa-20081128.pdf
Jan 26	comment	Hashing passwords with a salt - why use different salt for everyone? @JesperMortensen bruteforcing attacks against sufficiently large random strings (e.g. 16-32 byte) are infeasible. They apply to passwords because they don't have enough entropy. Your attack fails at step 2 if you don't know the "secret global salt" (which should be properly called "a key") if it has e.g. 128 bits of entropy. Of course, stealing this key is probably just as likely as stealing database. I'm just pointing out that your attack as described doesn't work.
Jan 26	revised	Using UMAC with stream cypher added 139 characters in body
Jan 26	answered	Using UMAC with stream cypher
Jan 26	revised	Hashing passwords with a salt - why use different salt for everyone? s/getting/building/
Jan 26	revised	Hashing passwords with a salt - why use different salt for everyone? Rephrase the whole answer
Jan 26	comment	Hashing passwords with a salt - why use different salt for everyone? Again, the question was: are there drawbacks in the system where we don't use /dev/urandom to generate salts? I listed them. I'll try to rephrase my answer.
Jan 26	comment	Hashing passwords with a salt - why use different salt for everyone? This answer to a bit different question on Security StackExchange is very good: security.stackexchange.com/questions/11221/…
Jan 26	revised	Hashing passwords with a salt - why use different salt for everyone? Highlight the main point.
Jan 26	comment	Hashing passwords with a salt - why use different salt for everyone? I considered the case of changing passwords later in the answer. We get system which leaks some information about passwords if there are multiple leaks of database. Is it bad? Yes. Is it better than a single per-database salt? Yes. Is it worse than random salt? Of course.
Jan 26	revised	Hashing passwords with a salt - why use different salt for everyone? added 2 characters in body
Jan 26	revised	Hashing passwords with a salt - why use different salt for everyone? Fixed sentence order
Jan 26	comment	Hashing passwords with a salt - why use different salt for everyone? @StephenTouset I'm not suggesting that it's a usable scheme. We're on Cryptography StackExchange, where we discuss a lot of theoretical stuff; otherwise we might as well replace the whole site with the page that says "use NaCl for encryption and scrypt for key derivation" ;)