10,719 reputation
11046
bio website vyznev.net
location Helsinki, Finland
age
visits member for 2 years, 8 months
seen 14 hours ago

I'm not really a cryptographer, I just play one on the internet.

Seriously, I'm just a programmer and mathematician interested in puzzles and information security. I don't have any kind of formal crypto training, but I've picked up a few things here and there over the years. Topics I'm particularly interested in include protocol design and analysis, classical ciphers and information-theoretically secure crypto techniques such as one time pads and secret sharing schemes.

Please consider any (original) code I post to Stack Overflow (and other Stack Exchange sites) to be released under CC-Zero unless stated otherwise. You may do whatever you want with it and don't have to credit me in any way, although of course that would be nice.


Jun
23
comment How does order-preserving encryption work?
Thanks for this excellent answer! I felt that it deserved more than just an accept and an upvote, so you'll be getting an extra 50 rep bounty on top of that in a day or so.
Jun
23
accepted How does order-preserving encryption work?
May
24
comment Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
@D.W.: I'm fairly sure that "Jim" in steps 2 and 3 should be "Bob", and have edited the question accordingly. I'm not sure what, if anything, the phrase "using his private key" as a whole is supposed to mean, though (unless perhaps it means that Bob signs the messages he encrypts with his (Bob's) private key).
May
24
revised Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
s/Jim/Bob/, see comments
May
10
revised What does $(\mathbb{Z}_n^*)^2$ mean?
edited tags
May
10
revised What kind of adversary is the cloud?
fix repeated misspelling, other minor copyedits
May
9
comment Increased CRC collision probability when adding bits to input message
@D.W.: Agreed, this question isn't really on topic here. Stack Overflow might be a better home for it.
May
9
comment Winzip AES256 vs PGP
In addition to the file names, encrypted ZIP archives also leak the sizes and last modification timestamps of the unencrypted files and, if the older AE-1 format is used, their CRC checksums. Also, since they're vulnerable to various attacks if the attacker can modify the archive. These slides summarize some of the possible vulnerabilities.
May
7
revised secret-sharing wiki excerpt
shorten excerpt; deleted 12 characters in body
May
7
revised How do you find a cheater in Shamir Secret Sharing?
edited tags
May
7
revised Implementing secret reconstruction in Shamir's Secret Sharing
better title, copyedit, add implementation tag
May
7
comment Indistinguishability attack example
@juaninf: $m^{(0)}=m^{(1)}$ is useless, since that guarantees that nobody can distinguish the messages (since they're identical!). Now, $m^{(0)}_0=m^{(0)}_1$, on the other hand...
May
7
reviewed Approve suggested edit on Indistinguishability attack example
May
5
answered Implementing secret reconstruction in Shamir's Secret Sharing
May
4
comment Is there a secure cryptosystem that can be performed mentally?
Ps. Here's a blog post I found with more details about the current security status of RC4. And yes, RC4-52 is probably less secure, and Solitaire even less so. They may both still be adequate for manual use (where messages are likely to be few and short), though.
May
4
comment Is there a secure cryptosystem that can be performed mentally?
@SmitJohnth: If used properly (derive the message key using a secure hash, and/or discard at least the first 768 or so bytes of output, don't encrypt more than about 1GB per message key), RC4 is still considered secure, in the sense of "no known practical attacks." I still wouldn't recommend it for new designs. Hand ciphers are kind of a special case, though: on one hand, one generally doesn't expect as much security from a hand cipher as from a computerized one; on the other, it would be quite hard for anyone to generate as much encrypted material by hand as most of the known attacks need.
May
3
answered Knowing a valid salted hash for an unknown secret, is it possible to compute another valid hash?
May
3
revised Knowing a valid salted hash for an unknown secret, is it possible to compute another valid hash?
texify, paragraph formatting
May
2
awarded  Nice Answer
Apr
30
revised Adversary Two Stages
quote formatting, add ind-cpa tag; needs further copyediting, but clarification from the OP would make that easier