220 reputation
28
bio website
location Tel Aviv, Israel
age 36
visits member for 2 years, 2 months
seen Oct 15 '13 at 15:02

Coding in Tel Aviv


Sep
24
awarded  Autobiographer
May
20
awarded  Notable Question
Jan
29
awarded  Yearling
Sep
14
awarded  Announcer
Jul
28
awarded  Nice Question
May
11
awarded  Popular Question
Aug
30
asked Do I have to have a different salt for each password?
Aug
30
comment How can I validate a hashed password if all I have is another hash?
SRP has minimal back-and-forth: Just two messages to derive a shared key. There are two more messages if you want authentication.
Aug
18
revised How do I store encrypted files on a web server and decrypt them locally?
I updated the resolution to half the PBKDF2 width
Aug
18
comment How do I store encrypted files on a web server and decrypt them locally?
Wow, I was surprised! PBKDF2 is very expensive to widen! jsperf.com/1-pbkdf2-versus-many-decrypts I'll drop the key authentication and just use the keys for decryption.
Aug
18
awarded  Editor
Aug
18
revised How do I store encrypted files on a web server and decrypt them locally?
Including a brief of my final resolution and offer for free code
Aug
18
accepted How do I store encrypted files on a web server and decrypt them locally?
Aug
18
comment How do I store encrypted files on a web server and decrypt them locally?
Regarding B, it depends which is more expensive to the user: Decrypting with a wrong key once per image (fast but many times) or doing the extra PBKDF2 (slow but just once).
Aug
18
comment How do I calculate the maximum plain text length allowable for a certain cipher text length?
Can VARCHAR(512) actually store 512 or does it need some sort of end-of-string marker?
Aug
17
comment How do I store encrypted files on a web server and decrypt them locally?
How come I need all the addition or modulo arithmetic? Couldn't I just use PBKDF2 to generate 512 bits, half which I would store in the index file for authentication, and the other half which I would use to decrypt the image's key? Per image I would store the first half of the 512 bits and the encryption of K_f. The advantage would be that I would only have to authenticate each password once, not once per file. The disadvantage: it would leak info about which files are encrypted with the same key. Other disadvantages?
Aug
17
awarded  Scholar
Aug
17
accepted Can I use PBKDF2 for authentication and decryption?
Aug
17
comment Can I use PBKDF2 for authentication and decryption?
The point about halving the attacker's workload is convincing!
Aug
17
awarded  Supporter