The DMZ

nealmcb

03:54

Very odd discussion, answer and conclusion to this one:

1

A: How to exchange RSA public keys safely between two parties?

There are a few easy options. Put the key or other data anywhere on the Internet, calculate a fingerprint for it via SHA-256 or some other decent hash, and communicate the fingerprint out-of-band with the other party: via a phone call, SMS, or perhaps email if you aren't too worried about someo...

Iszi

06:18

I can't find an "exact duplicate" for this question, but it seems it's been asked and answered a dozen different ways by now.

2

Q: How does varying character type increase strength of password?

When creating a new password, people often recommend you use both uppercase and lowercase characters, numbers, and symbols. How does adding any of these increase the strength of a password? There are 26 lowercase alphabet characters. Lets assume that there are 100 characters in the entire group...

passwords

AviD

10:07

@nealmcb done

@Iszi the question itself is not duplicate, but the answers on this one answer it well enough. I think the premise of this other question is based on @Jojo's question, but it doesnt state it explicitly.

11

Q: How reliable is a password strength checker?

I've tested the tool from Microsoft available here which tests password strength and rates them. For a password such as "i am going to have lunch tonight", the tool rates it's strength as "BEST" and for a password such as "th1$.v4l" it rates it as "Medium". I'm wondering how important password ...

passwords

so, close as duplicate because its asnwered there, or not close because its not the same question? its a tossup.

@RoryAlsop damn you @RoryAlsop, I wasted way too many hours rolling around laughing from that one ;)

my kids jumped out of bed to see whats wrong, when they heard me laughing at some of these... :D

@ScottPack I'm still not clear on your position on the partitioning q. borderline == keep it open regardless, or borderline == close it anyway?

Scott Pack

11:30

@AviD I suppose that's understandable. I strongly feel that the question that I think he's asking belongs on the site. The specific question in question, though, is poorly enough written that I'm rather on the fence about whether it's that one.

Scott Pack

13:21

@Iszi That was even your own question that you retweeted.

Iszi

@ScottPack I know. :-) Thanks for the tweet.

Scott Pack

Hey, it was a good question. I'm surprised that I hadn't seen it yet.

Iszi

@ScottPack Hadn't you? Could swear we'd talked about it in here.

Scott Pack

Well, I hadn't voted on it yet, which is a pretty good breadcrumb....

nealmcb

14:13

@ScottPack Which question?

Iszi

7

Q: "Phishing" red flags and countermeasures.

Given the recent spate of intrusions into various networks which have included compromise of subscriber identity and contact information, I figured it would be good for us to have a thread on how to spot and react to a "phishing" attempt. While the most common and prominent avenue for phishing i...

phishing

Scott Pack

Yes, that.

Thomas Pornin

Hello

5

Q: How many iterations of Rabin-Miller be used to generate cryptographic safe primes?

I am generating a 2048-bit safe prime for a Diffie-Hellman-type key, p such that p and (p-1)/2 are both prime. How few iterations of Rabin-Miller can I use on both p and (p-1)/2 and still be confident of a cryptographically strong key? In the research I've done I've heard everything from 6 to 6...

cryptography key-generation

is a duplicate of:

4

Q: How many iterations of Rabin-Miller should I use for cryptographic safe primes?

I am generating a 2048-bit safe prime for a Diffie-Hellman-type key, p such that p and (p-1)/2 are both prime. How few iterations of Rabin-Miller can I use on both p and (p-1)/2 and still be confident of a cryptographically strong key? In the research I've done I've heard everything from 6 to 64...

cryptography primes

I have answered to both with my faithful copy&paste, but I have a feeling this was not the right thing to do.

nealmcb

@ThomasPornin Borderline, but seems like a programming question to me

Scott Pack

And cross-posting. Nice.

Thomas Pornin

14:28

Apparently, the author and the only answerer of the Security.SE instance would be happy with a migrate-and-delete (remove the Security.SE version, move the SO question to Security.SE) but this requires mod-power.

nealmcb

but only now that I know the answer...

Scott Pack

I just voted and flagged it. Should catch somebody's attention.

nealmcb

Migrate to serverfault?

1

Q: How do you discover what permissions an AD group has, if you have no documentation?

You just got hired at company A and the old administrator is no longer there. Requests start coming through for adding users to the internet restrict group. When you look at the groups none of the names make sense and there is no documentation out there to explain what each group has rights to an...

windows active-directory

@ThomasPornin - I stumbled across this statement: cryptographers "have proved the existence of k-resilient Nash equilibrium in the secret sharing protocols". Even after looking at a few of the papers, I have no idea when one would want to use one of these schemes. Do you know?

Thomas Pornin

14:44

@nealmcb The problem of sharing a secret is not the sharing but the using.

A perfect sharing system has been known for more than 30 years (Shamir's scheme) but when the secret is rebuilt everybody learns it.

What is usually wanted is, for instance, a shared signature key such that a signature can be computed by the group (or an appropriate quorum) without any of the key holders learning anything about the key beyond his own share.

At that point, some of the key holders may want to collude into running the protocol with carefully chosen messages (possibly incorrect messages) in order to get more information on the shared secret.

So a group signature scheme (or group encryption or group whatever) must have a resilience towards malicious participants, up to a threshold which can be expressed with the terminology from game theory (hence "k-resilient Nash equilibrium").

An example would be a voting scheme with homomorphic encryption: votes are encrypted values, which can be added/multiplied together, and a bunch of trustees perform a group decryption on the result. We do not want any of the trustees to be able to decrypt the data by himself, even long after the vote itself.

Does that answer your question, or are you talking about something else ?

nealmcb

@ThomasPornin Ahh - so they get together, and share secrets, but don't ever see the symmetric key or whatever, and in each other's presence securely derive the result (winner), but know that no one can see the actual individual votes or something?

Thomas Pornin

@nealmcb Yes, something like that.

It depends on the scheme.

nealmcb

Still not quite seeing the connection though - this would allow you to not even need a mixnet to anonymize votes?

Thomas Pornin

Good schemes allow asynchronous operations (they exchange messages but this can be spread over a long amount of time).

@nealmcb Yes, homomorphic encryption with group decryption is an alternative to mixnets.

nealmcb

Sweet

Thomas Pornin

14:56

These are the two main structures for voting schemes.

Iszi

Does anyone have input on this one?

2 days ago, by Iszi

Should I post this here, or SU?: "Windows 7 - How to keep user IDs from being displayed on unauthenticated remote sessions?"

Thomas Pornin

@nealmcb Helios voting seems to use homomorphic encryption: heliosvoting.org

nealmcb

@ThomasPornin Ahh - cool - I've used that and reported some bugs and talked to Ben about Helios several times. Just didn't follow the path from the secret sharing to that application. Thanks!

Iszi

15:45

Anyone think this should have been migrated out?

4

Q: Resolving an IP address of a Remote machine to its MAC address

I wanted to know whether its possible to get the MAC address of remote node (computer/Access Point) if I know its IP address. I have heard that if someone sends you an email (even through gmail), you can find out the IP address (using the email headers), get the MAC address, and find out the exa...

network attack-prevention privacy

Anyone read this?

►

Scott Pack

19:49

Interesting fact. A grinding sound from the processor fan goes a long way towards explaining why a sensor suddenly goes offline.

nealmcb

20:38

@ThomasPornin If you have a good sense for how the game theory and recent work on k-resilient nash equilibria would fit in to:

Secret sharing

Secret sharing refers to method for distributing a secret amongst a group of participants, each of whom is allocated a share of the secret. The secret can be reconstructed only when a sufficient number of shares are combined together; individual shares are of no use on their own. More formally, in a secret sharing scheme there is one dealer and n players. The dealer gives a secret to the players, but only when specific conditions are fulfilled. The dealer accomplishes this by giving each player a share in such a way that any group of t (for threshold) or more players can together reco...

....let me know - I have a sense that that article could use some better organization

Thomas Pornin

@nealmcb Game theory is not my forte.

In the area of cryptography, what I was describing is usually known as "group signature" or "group decryption"

or more generally "multiparty computation"

although there are terminology subtleties

nealmcb

My curiosity was piqued by the reference to that phrase here: lca.epfl.ch/projects/gamesec

Hendrik Brummermann

21:59

Do I need to flag an offensive comment on an offensive answer or is it enough to just flag the answers?

Ninefingers

@HendrikBrummermann I would say flag both. Technically, if you leave a comment in the flag field, the moderators will be able to read that comment. I've flagged questions before now with comments such as "very extended discussion diverging off topic". On the other hand, flagging both helps because after so many (6?) flags, comments are automatically deleted.

nealmcb

23:19

Ooh - I've been missing two recent meta questions on black hat boundaries....

2

Q: What determines if a question should be considered Blackhat?

I asked this question recently which got a lot of votes and people thought was interesting, as well as some very interesting answers. It could have been the start of a very interesting discussion, except it was oddly closed for being "too blackhat". This is ridiculous. I asked only what techniq...

discussion acceptable-question

4

Q: How do we provide value to white and grey hats?

So it's something we're kicking around in chat for a while about a specific question, but I think it goes to the style of the site. We as a community are answering blackhat style questions. Do we want to impose a requirement that all questions regarding vulnerability exploitation also include a...

discussion acceptable-question asking-questions

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