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Cracking encrypted LastPass vaults

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Re: Cracking encrypted LastPass vaults

#31

Post by Anunayj »

iinnPP wrote: post #22

Does anyone have a good source on brute force and what is and isn't a good idea? I came across the below in a rather important website and am wondering if I should push harder for the to change it. How secure is a randomized 5 digit pin where you get unlimited guesses but after 10 guesses the pin is reset? Guessing the pin correctly gets you enough information to open a bank account. Assuming a system like the above…

> but after 10 guesses the pin is reset?

that does little to counter the real problem, as the chance of successfully guessing the pin on first try is still 1/1e5, which gives ~69k attempts for a 50% chance of correctly guess that pin, Which is like ~2 hr at 10 pin attempts/second. Having request throttling helps tremendously, but shouldn't be the only deterrence in place. Moreover it should be implemented in a way that it does not become a way for DoS attacks.

Re: Cracking encrypted LastPass vaults

#32

Post by Ekaros »

nerdawson wrote: post #26
xvector wrote: post #12

Earlier quoted context omitted.

The English dictionary has about 170k-1M words, and taking the log_2 of that gives us about 16-20 bits of entropy per word. Depending on implementation, we have anywhere from 80 to 100 bits of security. Even on the low end, it should take well over a decade if LastPass chose a good cryptographic hash function with a high iteration count. The problem is that no average person is gonna use a password that long to begin…

I think the other problem is that when people are thinking up “random” words on their own, they aren’t pulling from the English dictionary. Common vocabulary is a much smaller set.

About 20 000 active words is my understanding. And then the words people pick from is likely from fraction of that.

Re: Cracking encrypted LastPass vaults

#33

Post by pecheny »

selykg wrote: post #23
CommitSyn wrote: post #15

Earlier quoted context omitted.

As a LastPass user (that hasn't logged in since ~2015 :-/ ) can you explain the difference please? > This is why I prefer 1Password, as it requires the secret key to be compromised in addition to the Master Password, thus providing protection against a weak master password.

With 1Password you also have a randomly generated secret key. As I recall it’s a 128-bits, but could be wrong. To access your vault an attacker will need both your master password and the secret key. These are effectively combined to generate your keys for decryption. This protects against an attacker gaining access to 1Password servers. They can’t control whether you chose an awful password or not. So to protect the…

Sorry, I don't get it. The secret key has to be stored somewhere, right? If it's on the server, the attacker gets it together with the vault. If it's on the client, then you lose your phone → you lose your passwords, which is, while secure, very risky and I wouldn't expect it from a company focused on regular customers.

Re: Cracking encrypted LastPass vaults

#34

Post by croes »

agilob wrote: post #21
poglet wrote: post #18

Earlier quoted context omitted.

Agreed, it was a bit disappointing to get to the part where the password was added to the word list. The author does point out that a 2,000,000+ hashes per second could be achieved so it might give insight into how quickly all accounts will be checked against popular word lists. If I was a last pass customer I would be thinking about changing passwords on all accounts.

2,000,000+ H/s on macbook. I heard GPU clusters built purposely for quick hashing got cheaper recently.

2,000,000 on a multi GPU setup not a MacBook

Re: Cracking encrypted LastPass vaults

#35

Post by iinnPP »

hsbauauvhabzb wrote: post #28
iinnPP wrote: post #22

Does anyone have a good source on brute force and what is and isn't a good idea? I came across the below in a rather important website and am wondering if I should push harder for the to change it. How secure is a randomized 5 digit pin where you get unlimited guesses but after 10 guesses the pin is reset? Guessing the pin correctly gets you enough information to open a bank account. Assuming a system like the above…

What does the system hold? Your library loan history or nuclear weapon launch codes? Assuming it’s reset every 10 attempts, you have lost keyspace and gained random odds. 1:1000000 of getting the password right, 1:500k on average. Assuming I can perform one attempt per second, about 139 hours to successfully brute force a single account. One second is probably pessimistic, most systems are capable of serving much hig…

The pin is the MFA.

Is it 1000k or 10k (99999/10 guesses)?

I can't give full details of what is within accounts without potential exposure of the company. So I called a local bank and asked what I needed to set up an account. All the information required was part of a potential breach.

Is there a rate limit where protecting information with 5 digits is ok?

Re: Cracking encrypted LastPass vaults

#36

Post by [deleted] »

selykg wrote: post #23
CommitSyn wrote: post #15

Earlier quoted context omitted.

As a LastPass user (that hasn't logged in since ~2015 :-/ ) can you explain the difference please? > This is why I prefer 1Password, as it requires the secret key to be compromised in addition to the Master Password, thus providing protection against a weak master password.

With 1Password you also have a randomly generated secret key. As I recall it’s a 128-bits, but could be wrong. To access your vault an attacker will need both your master password and the secret key. These are effectively combined to generate your keys for decryption. This protects against an attacker gaining access to 1Password servers. They can’t control whether you chose an awful password or not. So to protect the…

[deleted]

Re: Cracking encrypted LastPass vaults

#37

Post by mattcoles »

agilob wrote: post #21
poglet wrote: post #18

Earlier quoted context omitted.

Agreed, it was a bit disappointing to get to the part where the password was added to the word list. The author does point out that a 2,000,000+ hashes per second could be achieved so it might give insight into how quickly all accounts will be checked against popular word lists. If I was a last pass customer I would be thinking about changing passwords on all accounts.

2,000,000+ H/s on macbook. I heard GPU clusters built purposely for quick hashing got cheaper recently.

He didn’t achieve 2MH/s on his MacBook. That was the authors estimate of what you could achieve on a multi-GPU setup, it was only around ~1KH/s on the MacBook.

Re: Cracking encrypted LastPass vaults

#38

Post by poglet »

pecheny wrote: post #33
selykg wrote: post #23

Earlier quoted context omitted.

With 1Password you also have a randomly generated secret key. As I recall it’s a 128-bits, but could be wrong. To access your vault an attacker will need both your master password and the secret key. These are effectively combined to generate your keys for decryption. This protects against an attacker gaining access to 1Password servers. They can’t control whether you chose an awful password or not. So to protect the…

Sorry, I don't get it. The secret key has to be stored somewhere, right? If it's on the server, the attacker gets it together with the vault. If it's on the client, then you lose your phone → you lose your passwords, which is, while secure, very risky and I wouldn't expect it from a company focused on regular customers.

It sounds like a public and private key pair, like in asymmetric encryption or public-key cryptography. The private key is stored on the client. The private key and users password are both required to authenticate against the public key stored the server.

An attacker would have no success with a dictionary attack (used in the article). Even if the password was in the dictionary, the private key is still missing.

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