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524
bio website touset.org
location San Francisco, CA
age 30
visits member for 2 years
seen 18 hours ago

Cyclist. Rubyist.


Sep
6
comment What is the most secure key expansion routine?
No key expansion (nor any computable function) can return a value with more entropy than what is input. The "best" you can accomplish (for some definition of the term) to is distribute the entropy evenly across the entire output.
Sep
6
comment What is the most secure key expansion routine?
A hash function is a function or method in a programmatic sense. It accepts an input, performs some bounded amount computation, and returns an output. What are the actual criteria you're looking for?
Sep
5
comment What is the most secure key expansion routine?
A hash function is a function. I don't think your expectations are very clear.
Sep
5
comment Base64 for a hash algorithm
I get the feeling that your question is poking at the surface of a deeper issue you're trying to understand. What's the context, and why is the nomenclature important here?
Sep
5
comment Using SHA-256 with different initial hash value
Why not simply use HMAC or NMAC, then, which have security proofs?
Sep
5
comment Using SHA-256 with different initial hash value
What would be the benefits?
Sep
4
comment Change Salt when Changing Password?
Independent of the rest of the question, salts should always change when a password is changed.
Aug
28
comment Why are some key stretching methods better than others?
Really? Your question here quotes the entire section I removed, asking for clarification of exactly why the given pseudocode has the properties claimed.
Aug
28
comment Repeatable crypto
Also, you may wish to look into the architecture of tarsnap, which was designed to efficiently solve content-aware deduplication of encrypted backups.
Aug
28
comment Why are some key stretching methods better than others?
For what it's worth, I've removed those algorithms from the Wikipedia page. Wikipedia should not be encouraging amateurs to implement their own bespoke key stretching algorithms.
Aug
27
awarded  Nice Answer
Aug
27
comment PBKDF2-SHA256+SHA256 for password storage
That's also possible by storing a random key in the user's cookies and comparing it against the hash of that key in the database. Or by HMACing the session cookie with an in-memory key.
Aug
26
comment PBKDF2-SHA256+SHA256 for password storage
What is gained by tying the session cookie to the user's password in any way?
Aug
26
comment How is SHA1 different from MD5?
With regard to your last statement, what about BLAKE2b? It claims to be faster even than MD5. Is this only due to taking special advantage of modern hardware, or the result of "working smarter, not harder"?
Aug
26
comment PBKDF2 Salt and Password Ordering
That's fair. :) There are a lot of questions here that are thinly-veiled fronts for, "I think I know more than experienced cryptographers, and would like to use preexisting algorithms in strange and confusing ways to increase their security. Is anyone here willing to validate my decisions?" It's useful to weed these types of questions out.
Aug
26
comment What are the advantages of CBC over ECB?
Additionally, clever chosen-plaintext attacks against ECB can reveal plaintexts in $O(n)$.
Aug
26
comment PBKDF2 Salt and Password Ordering
Does it matter? One of these approaches has withstood years of use and examination by cryptographers. The other has not.
Aug
25
revised Found a way to crack AES-128, what now?
edited body
Aug
25
answered Found a way to crack AES-128, what now?
Aug
19
comment Using HMAC-SHA256 with short passwords and sliced outputs for short-lived secure hashing
It doesn't matter what the original hash length was. Trimming the output of a random oracle to $n$ bits will cause it to require $2^{n-1}$ operations on average to find a collision for a particular output, and $2^{n/2}$ operations on average to find any collision.