Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

"Pwned Passwords" V2 With Half a Billion Passwords

troyhunt.com

Post reply on HN
Print view View original

201–210 of 369 posts

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#201

Post by jasonpeacock »

royce wrote: post #175
kbenson wrote: post #171

Earlier quoted context omitted.

> his API does not allow the implementor to specify a frequency threshold Yes it does. The output contains the number of matching passwords. It's just client side instead of server side. The reason for not doing so on the server is also obvious taking into account his explanation of cost and caching, which informed much of the API design itself. > By both API and explicit language in the announcement, he is promulgat…

It's a fair point that raw password count is available. But that value is an absolute number, without any in-API context of the total size of the corpus. This makes expressing relative rarity only possible by hard-coding the total size of the corpus into a calculation. Put another way: the 20,000th position has a frequency value of "7889". But what does that mean ? Where is that in the distribution of password freque…

I don't follow - how is the relative rarity better than absolute frequency? What really matters is how common your password is - not how highly it's ranked in a compromised password list, which has no relevance to how common it may be.

You want to filter on users choosing a password that's been re-used across all compromised more than N times.

Filtering users on choosing a password that ranks N of M on a list of compromised passwords doesn't tell the user how bad that password is.

In fact, once you get to the rail, the ranking is basically based on sort order and become irrelevant?

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#202

Post by stordoff »

zaroth wrote: post #39

I'm going to have to disagree with the premise that sites should stop users from choosing a password which happens to have been cracked offline at some point in the past -- to the tune of blacklisting half a billion potential secrets. What exactly is the end goal, and at what cost? Well, there are 3 ways to steal a password. You can steal it from the user -- either by phishing or with malware -- in which case it matt…

> How many attempts on average would it take a user to find a password which was not rejected? [...] I'll say one more thing on the idea of blacklists. Users just trivially work around them. Password quality (entropy, guessability) does not generally increase. Bad password policies often decrease password quality, particularly in the case of password expiry.

That was my concern - if this blacklist is used widely,could it _encourage_ password reuse? If it takes multiple attempts to find a valid password, will the user just find one that is accepted and then use it everywhere?

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#203

Post by rspeer »

royce wrote: post #156
kbenson wrote: post #153

Earlier quoted context omitted.

> I tried to encourage Troy to suggest to implementors that blacklisting all passwords was a Bad Idea. Instead, he doubled down > Please don't use the entire list for blacklisting unless you actively also guide the user in how to generate a random passphrase (if a human must remember it) or a random password (if it will be stored in a password manager). I think he did the right thing, and think you are correct as wel…

As a corpus to download for password research, this is indeed useful. But for providing a blacklist -- his stated purpose - it is not. The crucial tell: his API does not allow the implementor to specify a frequency threshold (by top X in the list, or by Y number of unique uses of the password or higher). By both API and explicit language in the announcement, he is promulgating the idea that checking the entire blackl…

This list is small for the purposes of password-cracking. Enumerating 500 million things is something a computer can do very quickly.

Consider this: if you store the hash of one of these passwords in your login database, you have stored something that can quickly be turned back into the plaintext password, just by enumerating the list.

Passwords that have been leaked can't become good passwords again.

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#204

Post by rspeer »

royce wrote: post #175
kbenson wrote: post #171

Earlier quoted context omitted.

> his API does not allow the implementor to specify a frequency threshold Yes it does. The output contains the number of matching passwords. It's just client side instead of server side. The reason for not doing so on the server is also obvious taking into account his explanation of cost and caching, which informed much of the API design itself. > By both API and explicit language in the announcement, he is promulgat…

It's a fair point that raw password count is available. But that value is an absolute number, without any in-API context of the total size of the corpus. This makes expressing relative rarity only possible by hard-coding the total size of the corpus into a calculation. Put another way: the 20,000th position has a frequency value of "7889". But what does that mean ? Where is that in the distribution of password freque…

Why would a password that occurs in this list, but rarely, be safer? Attackers aren't going to skip the rare ones.

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#205

Post by eof »

This is a tangent; but I had a 'pwned' password that I've used for years on steam that started getting hacked like 4-5x a week; I would just ignore the 2 factor attempts for several months.

I finally changed the password to a slight variation that is not in this list (nor likely any others, 9 random alphanumerics); and within a week the two factor notifications started back up!

I was really surprised; admittedly the modification was trivial, but that is pretty thorough for a steam account I've spent like $100 in.

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#206

Post by eof »

ivanech wrote: post #170

I think it would be interesting to do an art project with this data - some of these passwords are funny and/or revealing. Some examples: pooplasagna - 3 times eggsarebad - 3 times eggsaregood - 25 times myhusbandcheats - 4 times icheatonmywife - 1 time ihatemyneighbors - 2 times iamanalcoholic - 6 times 1yearsober - 31 times imissmykids - 51 times imissmyparents - 6 times

hunter7 - 7935 times

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#207

Post by caf »

royce wrote: post #143

The UX of a blacklist with a half billion entries would be so crippling that it would cause a user revolt. Most people's password-selection strategies are similar enough to other people's (like kbenson's 4000+ hit) that they could spend hours trying to come up with a password that has never been leaked before. I tried to encourage Troy to suggest to implementors that blacklisting all passwords was a Bad Idea. Instead…

Rather than "I am right and Troy is wrong", this seems to be a case of "reasonable people may disagree".

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#209

Post by kbenson »

febed wrote: post #138
ChrisSD wrote: post #41

Earlier quoted context omitted.

As stated in the post, it's a simple solution to help with anonymity. "The password has been hashed client side and just the first 5 characters passed to the API As mentioned earlier, there are 475 hashes beginning with "21BD1", but only 1 which matches the remainder of the hash for "P@ssw0rd" and that record indicates that the password has previously been seen 47,205 times."

But Troy could still very easily guess the complete hash. It's the one with the 47,205 hits.

But's it's not always that hash. The password you're checking may not be on the list. This is just a quick check to see if the password in question is on the list, in which case it may be a poor choice depending on how often it's seen.

For example, say I want to check "gSAey27tgGsaEG". That hashes to c2e5dfb023cd42df94751581cba33b24bc011027. https://api.pwnedpasswords.com/range/c2e5d has no entry for fb023cd42df94751581cba33b24bc011027, so it's not even in the list of passwords.

Put another way, it averages a few hundred hashes per prefix based on the total password list size (~500M), but there's 2^136 possible has suffixes per prefix. There's no point in guessing that.

Re: "Pwned Passwords" V2 With Half a Billion Passwords

#210

Post by MBCook »

ravenstine wrote: post #165
odammit wrote: post #162

If you spend the time building a system to search those half billion passwords when you’re users are signing up, you should focus on building a login rate limiting system so it’s not possible to brute force someone’s password.

I think this is intended for the case where a database has been compromised, but then again, I thought that hash algorithms and salting were supposed to deal with that.

IF people actually do that correctly, yes. But history has proven many sites (big and small) are quite happy to send you your plaintext password.
Post reply on HN