Reputation
1,579
Top tag
Next privilege 2,000 Rep.
Access moderator tools
Badges
1 8 17
Impact
~43k people reached

Oct
9
comment AES file encryption with PBKDF2. Safe parameters?
@CodesInChaos I'm pretty sure we're on the same page: perform as many iterations of PBKDF2 as tolerable requesting output equal to the native size of the underlying hash, and then a final single iteration requesting however many bytes are required.
Oct
9
comment AES file encryption with PBKDF2. Safe parameters?
@CodesInChaos - yup, hence 512 bits of output only for the final round (256 bits for every other round). I'm a big fan of HKDF too - but seeing as though PBKDF2 is required here anyway, it seems cleaner to me to use it for the final step.
Oct
9
comment what are the uses of tweaks in block ciphers?
Related: crypto.stackexchange.com/questions/6185/…
Oct
9
comment AES file encryption with PBKDF2. Safe parameters?
"HMAC-SHA256 with the content's encryption key" - naughty. Never use the same key for two different crypto primitives. Upon completion of your PBKDF2 rounds, perform a final round, but ask for 512 bits of output. Use the first 256 bits for the encryption key, and the rest for the HMAC key. More info here. As mentioned, if it's available, authenticated encryption such as CCM, EAX, GCM or OCB is also a good option.
Oct
2
comment NIST temporarily closed — will that have a negative impact on the future of cryptography?
i.imgur.com/LO4yypb.png
Sep
28
awarded  Popular Question
Sep
23
comment What is the security loss from reducing Rijndael to 128 bits block size from 256 bits?
crypto.stackexchange.com/questions/6016/…
Sep
21
comment With a true random number generator at hand, how to implement one-time pad?
It's explained in more detail than you could possibly hope for in wikipedia.
Sep
20
comment Why is AES considered to be secure?
Given the recent NSA scandal - I think that last point is more pertinent than ever.
Sep
20
comment Can I use SHA1 as license key?
@user8534 - I wouldn't go so far as to say it's impossible, but if you use a 2048+ bit key, it's a pretty safe bet.
Sep
20
answered Can I use SHA1 as license key?
Sep
15
comment bcrypt and pbkdf2 double hashing
@ytti - Perhaps bcrypt and scrypt aren't that common (scrypt less so), but pbkdf2 is very widely used - it's even been standardized.
Sep
12
comment Combining multiple symmetric encryption algorithms - implications?
There's some excellent discussion of this topic here
Sep
12
revised Can I dynamically calculate an appropriate number of iterations for PBKDF2 based on the system time, rather than using a fixed value?
added 103 characters in body
Sep
12
answered Can I dynamically calculate an appropriate number of iterations for PBKDF2 based on the system time, rather than using a fixed value?
Sep
6
comment Is javascript RSA signing safe?
The point that @CodesInChaos is making is that the javascript source code itself (and not just the user data) needs to be downloaded by the client over HTTPS, otherwise it can be modified in transit to behave in a malicious way. Read this before proceeding.
Sep
3
answered Using one-way hash functions as the encryption method
Aug
29
comment The security of an encrypt-and-MAC
Very closely related: crypto.stackexchange.com/questions/202/…
Aug
24
comment Do ciphertexts leak information about their algorithmic creators?
"Many encryption algorithms overtly leak their identity" - which ones?
Aug
19
comment OMAC/CMAC constant for different block sizes
the crypto++ implementation of CMAC specifies the constants for 64, 128, and 256-bit block sizes, if that's any help.