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Double Blind Passwords a.k.a. Horcruxing

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Re: Double Blind Passwords a.k.a. Horcruxing

#71

Post by chairmanwow1 »

vmarquet wrote: post #70
chipsa wrote: post #46

I saw this post a while ago in a different forum. My note for it hasn't changed: This is called peppering[0]. It's a counterpart to salting, in that you add a random value to a password to make it harder to reverse the password hash, but unlike the salt, it's not stored in the password database. 0: https://en.wikipedia.org/wiki/Pepper_(cryptography)

I think the term "peppering" is mostly used for server side manipulation of the password, which the user is unaware of. It would be very confusing to reuse this term for what is described in this article, so a new term like "Horcruxing" can be relevant. I like it.

I think I really disagree with you there. This is the same concept but applied client-side instead of server-side.

But “client-side peppering” won’t get you to the front page of HN..

Re: Double Blind Passwords a.k.a. Horcruxing

#72

Post by starfallg »

TwoBit wrote: post #59
Thorrez wrote: post #28

If there's generic malware that's targeting your password manager, then yes this provides protection against that. But it doesn't provide protection against a targeted attack, because the malware can just keylog your horcrux. Another weakness that doesn't require a keylogger, is the attacker might be able to find some stolen database of a website that stored passwords in plaintext, then deduce your horcrux from the d…

> attacker can create a website and ask you to join it under the hope you'll reuse your horcrux on the attacker's site. I don't think that reusing the same pepper (horcrux string) for all sites would be best practice.

That defeats the point of using a password manager more or less. You're just remembering individial passwords but it's even more complicated now.

Re: Double Blind Passwords a.k.a. Horcruxing

#73

Post by ignoramous »

Cloudflare published a fantastic piece on passwords (viz. OPAQUE) recently that got little to no attention on news.yc, unfortunately [0].

OPAQUE + Horcux sounds pretty close to what Signal did for its app passwords [1].

[0] https://news.ycombinator.com/item?id=25346632

[1] https://news.ycombinator.com/item?id=21839117

Re: Double Blind Passwords a.k.a. Horcruxing

#76

Post by thaumaturgy »

This is not an improvement over just using the click-to-login features of modern password managers.

Modern password managers generate strong random passwords and integrate with login forms in your desktop browser and on your mobile device. There are some exceptions with sites or applications that don't behave well, but as a general rule: you should not ever need to know any of your passwords anyway.

You should be clicking on whatever little icon is attached to login forms so that your password manager can autofill it for you. There shouldn't be an opportunity to add something to a password during login; you're just adding friction to a process that should be as frictionless as possible, because friction causes people to make bad decisions.

If the concern is that someone might be able to access your password manager, you should think harder about what it would mean for someone to have that level of access to your devices or data.

> [What if] your master password (the password to your password manager) is compromised...

Remote access for cloud-sync'd password managers should all have 2FA enabled anyway. You shouldn't be using anything even remotely simple for your master password. Local access to your password manager means you're screwed.

> [What if] someone gained temporary access to your unlocked system (computer or phone) when you stepped away

This is weird. Is this a thing? Are there people with private data in public environments who don't have the presence of mind to take their devices with them in to the bathroom but do have the presence of mind to dick about with their passwords every time they have to sign in to something? I'd pretty comfortably wager there's a much larger real risk from skilled phishing than from somebody in a hoodie rushing over while you're on the can regretting last night's last-minute Taco Bell trip.

Re: Double Blind Passwords a.k.a. Horcruxing

#77

Post by Aachen »

anonymouse008 wrote: post #60
nullc wrote: post #15

Double blind is the wrong term here. Multi-factor would be appropriate.

With a degree of complexity removed since the key doesn’t change over time.

Removed? Do you regularly change passwords?

I can see the point when using a password manager, though it's typically overkill, but please be aware that forcing memorized secrets to be changed arbitrarily (e.g. time-based) is recommended not to do in the updated guidelines from USA's NIST, UK's NCSC, Microsoft, and others based on research into what effect it has on password quality.

Re: Double Blind Passwords a.k.a. Horcruxing

#78

Post by withinboredom »

TheDong wrote: post #19
phantom_rehan wrote: post #6

Earlier quoted context omitted.

Older and weaker hashing algorithms are probably better for this, sha384 and upwards produce large hashes that might be too big for passwords for some websites. Protonmail trims anything more than 72 characters. See - https://www.reddit.com/r/ProtonMail/comments/khrzhe/pm_ignor...

This isn't good security advice. Taking trunc(32, hex(sha512)) will still give you a result that is stronger cryptographically than taking the 32 characters hex(md5sum) would give you. For more security, you of course can encode the sha512 hash in a format other than hex in order to let those 64 bytes be fewer characters. The hex encoding is only one of many encodings. But the main point is that the solution to needi…

This is even worse advice! If you have a small input, you want a hashing function that matches that size[1] of the input as closely as possible. Collisions aren't important here (so "strength" isn't important), just the randomness. MD5 and SHA families give you (mostly) random distributions. The bias in the results are practically meaningless.

[1] https://crypto.stackexchange.com/questions/12822/are-the-sha...

Re: Double Blind Passwords a.k.a. Horcruxing

#79

Post by djeiasbsbo »

toasted_flakes wrote: post #64
TwoBit wrote: post #59

Earlier quoted context omitted.

> attacker can create a website and ask you to join it under the hope you'll reuse your horcrux on the attacker's site. I don't think that reusing the same pepper (horcrux string) for all sites would be best practice.

If only we had a secure place to store all of the horcrux strings that are unique per-website! Joking aside, I don't see the point of this. It guards against exactly one attack (your password manager somehow revealing all your passwords) which is unlikely, but not against a whole lot of other (slightly more generic malware, phishing, ...) whilst making logging in harder (there's now a manual process). If you're willi…

That might be likely if the password manager database is stored in the cloud. iCloud hacks seem to be at least somewhat common and iOS users often hsve no other means of syncing their password manager database.

Re: Double Blind Passwords a.k.a. Horcruxing

#80

Post by StavrosK »

Dylan16807 wrote: post #57
war1025 wrote: post #10

Earlier quoted context omitted.

I thought that algorithm was crazy magic when I first heard of it. The method behind it is pretty fascinating. A nth degree polynomial is uniquely identified by n+1 points. So the algorithm interprets your secret to a binary numeric value, sets that as the value at x=0 (i.e. the constant term of the polynomial), picks random coefficients for all the polynomial degrees, then computes coordinate pairs for however many…

While it's a clever method, it's also worth noting that for moderately-sized groups you can achieve the same thing with a much simpler method and almost no math. Let's say you have a 256 bit key as the secret, and you want any 5 out of 15 people to have access. For each combination of 5 people, pick 4 random 256 bit numbers. 4 people get those and 1 gets the key encrypted with those numbers as a one time pad. Once yo…

What happens if 5 people who have encrypted random numbers (and no key) get together?
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