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Double Blind Passwords a.k.a. Horcruxing

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

#11

Post by vinay_ys »

It is much better to use a password manager than trying to remember poorly crafted passwords in your head. But also really/truly remember not to really put all your eggs in one proverbial basket.

Password managers are not without dangers:

1. If you forget your master password or secret key (you need both to setup a new device), you are screwed.

2. If the password manager cloud sync service (like 1password) decides to cancel your account for whatever reason, you are screwed.

3. If the password manager allows silently keeping replicas on devices you don't know about, you are screwed.

4. If your password manager logs your sign-in access patterns along with your IP addresses (even from behind your fancy VPNs), you are screwed.

5. If you are storing your password, your 2FA secret, and your recovery keys - all in the same password manager, you are royally screwed when that password manager is compromised.

6. If you lose your device, or device gets damaged etc and you don't have a copy of your vault, you are screwed.

Remember – supply chain attacks (example: password manager company's office gets hacked, and their signing key gets stolen and a trojan update is delivered to your machine) will happen some day (may have already happened) and all your passwords will be stolen. Just assume that and behave accordingly.

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

#13

Post by sasaf5 »

war1025 wrote: post #10
emmanueloga_ wrote: post #7

This is a cool/useful idea. I thought the article was gonna be about "Shamir's Secret Sharing" [1], "where a secret is divided into parts, giving each participant its own unique part. To reconstruct the original secret, a minimum number of parts is required.". Sounds horcruxy to me :-p. I learnt about it from the PIM book [2]. 1: https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing 2: https://pimbook.org/

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…

Your description made it click for me too! Thank you!

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

#14

Post by hn_throwaway_99 »

phantom_rehan wrote: post #6
bootlooped wrote: post #5

If you hash the concatenated string result, and use the hash as your password, it also means your horcrux wouldn't be at all visible to services. That's a lot of extra work though.

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...

Just take the first n characters of the hash then.

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

#16

Post by nullc »

war1025 wrote: post #10
emmanueloga_ wrote: post #7

This is a cool/useful idea. I thought the article was gonna be about "Shamir's Secret Sharing" [1], "where a secret is divided into parts, giving each participant its own unique part. To reconstruct the original secret, a minimum number of parts is required.". Sounds horcruxy to me :-p. I learnt about it from the PIM book [2]. 1: https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing 2: https://pimbook.org/

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…

"Cool value" often makes for poor security however. The same kind of excitement you felt goes on to cause people to homebrew insecure versions or inappropriately deploy Shamir's Secret Sharing.

https://en.bitcoin.it/wiki/Shamir_Secret_Snakeoil

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

#17

Post by tobib »

vinay_ys wrote: post #11

It is much better to use a password manager than trying to remember poorly crafted passwords in your head. But also really/truly remember not to really put all your eggs in one proverbial basket. Password managers are not without dangers: 1. If you forget your master password or secret key (you need both to setup a new device), you are screwed. 2. If the password manager cloud sync service (like 1password) decides to…

> 4. If your password manager logs your sign-in access patterns along with your IP addresses (even from behind your fancy VPNs), you are screwed.

Can you explain why one would be screwed in this case?

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

#19

Post by TheDong »

phantom_rehan wrote: post #6
bootlooped wrote: post #5

If you hash the concatenated string result, and use the hash as your password, it also means your horcrux wouldn't be at all visible to services. That's a lot of extra work though.

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 needing to store a shorter value is not to use a weaker hashing algorithm, but to truncate the result.

This is the reason that sha-512/256 exists as a truncated sha-512 even though sha-256 already existed.

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