210 reputation
17
bio website
location Tel Aviv, Israel
age 36
visits member for 1 year, 8 months
seen Oct 15 '13 at 15:02

Coding in Tel Aviv


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
Aug
16
awarded  Student
Aug
16
comment How do I store encrypted files on a web server and decrypt them locally?
I like the idea of being able to change the password without modifying all the images, though. That's pretty cool!