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Can someone point out a big flaw in my password management system? I have always felt kinda dumb for not using a PW manager but my system has worked for the las

Can someone point out a big flaw in my password management system? I have always felt kinda dumb for not using a PW manager but my system has worked for the last ~10+ years and I have never had any issues. I memorized a small function that takes the product name as input and spits out a password. it achieves the goal of having a unique pw for every service without having to write anything down (in software or on paper). I had to amend it to account for some services that require you to reset your password to a new one and for sites with annoyingly specific password formats (i.e. 3 special chars).

deleted 4y ago
[deleted]
darrenf 4y ago
Not necessarily a huge flaw and indeed it’s a method I used for a long time too - but what it doesn’t really help with is when there’s a breach and one of your passwords is in a leak. What do you do: make (and remember) an exception and the second choice function? Or change all your passwords so an amended function still holds true for all sites? With a password manager you just change the breached one and that’s it.
robust-cactus 4y ago
This is pretty cool, and could even make a great "no storage" type product here. Hmm 1 problem could be forced password changes? I've noticed some sites at times require password changes.
- drexlspivey 4y ago
  It’s not, you can guess all his passwords if you know a couple of existing passwords (maybe even 1)
deepserket 4y ago
> function that takes the product name as input and spits out a password Can someone infer the function starting from the password and the service name? If yes, then there is a low (close to zero, unless you are specifically targeted) possibility to gain a clear password from a shitty website and calculate your other passwords.
flandish 4y ago
What about when a product changes names, between your logins? Take protonmail - they started to use “proton.me” instead of “protonmail.com” more and more often. If your f(x) was f(“protonmail”) originally but after being away six months you try in the middle of the night while hungover and driving in snow f(“proton”) won’t get the same result?
temuze 4y ago
I used to do a similar thing, then I realized it was a potential problem. Let's say you have an account at AcmeCo. Let's say AcmeCo has a breach and I can see your password hash. Let's say the company uses a weak password hash (e.g. MD5), or no salt and it's easy to reference a rainbow table. From this rainbow table, I can look up your hash and see that your password is "lulzSecret2$AcmeCo". Now let's say you're in another leak from BetaCo. Similar situation -- I see that your password is "lulzSecret2$BetaCo2". Maybe the two is because you were forced to rotate your password once. It doesn't take a genius to guess what your algorithm is. But we can take it another level. Maybe I'll try all the major banks and guess passwords using your algorithm ("lulzSecret2$bofa", "lulzSecret2$chase"). Most banks require 2fa, but most of the time they keep it to text-based 2fa. If I know your phone number from one of the breaches (happens all the time), maybe I can hijack your SIM card (this also happens all the time) and boom, I'm into your bank account.
- snotrockets 4y ago
  Assume the function is a cryptographically appropriate hash function, you can reduce the risk of suggested attack to almost nil, considering the number of inputs you'd need for such attack
IncRnd 4y ago
> Can someone point out a big flaw in my password management system? The issue is that your passwords have almost zero entropy in them. The only guard is that others don't know your secret function. Password crackers are already programmed to handle functional password composition. You might want to ask yourself why pw crackers are programmed that way.
- grogenaut 4y ago
  Taken in isolation they might have a ton of entropy, just not taken across leaked password databases.
  - drexlspivey 4y ago
    If my password is hunter2#gmaildotcom for gmail what could my reddit password be? It doesn’t take many leaks to crack the formula.
    - grogenaut 4y ago
      Yes but is someone specifically looking at your passwords across all the accounts I'm trying to crack them or are they just taking the easy road and trying those same passwords and every other site. One requires a lot more effort than the other while still being relatively easy. Generally people do not have specific attackers going after them they are going after broad spectrum attackers you don't have to be faster than the bear you just have to be faster than the other person running from the bear. And yes I'm not saying that's actually secure I'm just pointing out a consideration. Also there are different classes of passwords out there email and password for marketing site I'm never going to use again but I'm forced to sign up for versus something that actually is protecting something I care about like my credit card or worse my financials.
grogenaut 4y ago
Can't reuse a previous password is a great signal of what your password actually is. There are a lot of sites with dumb rules like can't be more than 8 characters (old WSDOT toll rule) or can't have symbols... So it doesn't always work.
snotrockets 4y ago
I used to use a similar system (http://crypto.stanford.edu/PwdHash/pwdhash.pdf http://crypto.stanford.edu/PwdHash/pwdhash.pdf), until I realized it has a glaring issue when passwords need be rotated. Assume a service you use was breached, and you have to replace your password there. You can work around it by having another input to your generator. Instead of (master password, service), you now have (master password, service, version). Maybe you append the version into one of the other arguments to keep the function the same; doesn't matter: now there's a new, per-service argument you have to track and remember.

deleted 4y ago

[deleted]

darrenf 4y ago

Not necessarily a huge flaw and indeed it’s a method I used for a long time too - but what it doesn’t really help with is when there’s a breach and one of your passwords is in a leak. What do you do: make (and remember) an exception and the second choice function? Or change all your passwords so an amended function still holds true for all sites? With a password manager you just change the breached one and that’s it.

robust-cactus 4y ago

This is pretty cool, and could even make a great "no storage" type product here. Hmm 1 problem could be forced password changes? I've noticed some sites at times require password changes.

drexlspivey 4y ago
It’s not, you can guess all his passwords if you know a couple of existing passwords (maybe even 1)

deepserket 4y ago

> function that takes the product name as input and spits out a password Can someone infer the function starting from the password and the service name? If yes, then there is a low (close to zero, unless you are specifically targeted) possibility to gain a clear password from a shitty website and calculate your other passwords.

flandish 4y ago

What about when a product changes names, between your logins? Take protonmail - they started to use “proton.me” instead of “protonmail.com” more and more often. If your f(x) was f(“protonmail”) originally but after being away six months you try in the middle of the night while hungover and driving in snow f(“proton”) won’t get the same result?

temuze 4y ago

I used to do a similar thing, then I realized it was a potential problem. Let's say you have an account at AcmeCo. Let's say AcmeCo has a breach and I can see your password hash. Let's say the company uses a weak password hash (e.g. MD5), or no salt and it's easy to reference a rainbow table. From this rainbow table, I can look up your hash and see that your password is "lulzSecret2$AcmeCo". Now let's say you're in another leak from BetaCo. Similar situation -- I see that your password is "lulzSecret2$BetaCo2". Maybe the two is because you were forced to rotate your password once. It doesn't take a genius to guess what your algorithm is. But we can take it another level. Maybe I'll try all the major banks and guess passwords using your algorithm ("lulzSecret2$bofa", "lulzSecret2$chase"). Most banks require 2fa, but most of the time they keep it to text-based 2fa. If I know your phone number from one of the breaches (happens all the time), maybe I can hijack your SIM card (this also happens all the time) and boom, I'm into your bank account.

snotrockets 4y ago
Assume the function is a cryptographically appropriate hash function, you can reduce the risk of suggested attack to almost nil, considering the number of inputs you'd need for such attack

IncRnd 4y ago

> Can someone point out a big flaw in my password management system? The issue is that your passwords have almost zero entropy in them. The only guard is that others don't know your secret function. Password crackers are already programmed to handle functional password composition. You might want to ask yourself why pw crackers are programmed that way.

grogenaut 4y ago
Taken in isolation they might have a ton of entropy, just not taken across leaked password databases.
- drexlspivey 4y ago
  If my password is hunter2#gmaildotcom for gmail what could my reddit password be? It doesn’t take many leaks to crack the formula.
  - grogenaut 4y ago
    Yes but is someone specifically looking at your passwords across all the accounts I'm trying to crack them or are they just taking the easy road and trying those same passwords and every other site. One requires a lot more effort than the other while still being relatively easy. Generally people do not have specific attackers going after them they are going after broad spectrum attackers you don't have to be faster than the bear you just have to be faster than the other person running from the bear. And yes I'm not saying that's actually secure I'm just pointing out a consideration. Also there are different classes of passwords out there email and password for marketing site I'm never going to use again but I'm forced to sign up for versus something that actually is protecting something I care about like my credit card or worse my financials.

grogenaut 4y ago

Can't reuse a previous password is a great signal of what your password actually is. There are a lot of sites with dumb rules like can't be more than 8 characters (old WSDOT toll rule) or can't have symbols... So it doesn't always work.

snotrockets 4y ago

I used to use a similar system (http://crypto.stanford.edu/PwdHash/pwdhash.pdf http://crypto.stanford.edu/PwdHash/pwdhash.pdf), until I realized it has a glaring issue when passwords need be rotated. Assume a service you use was breached, and you have to replace your password there. You can work around it by having another input to your generator. Instead of (master password, service), you now have (master password, service, version). Maybe you append the version into one of the other arguments to keep the function the same; doesn't matter: now there's a new, per-service argument you have to track and remember.