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MiniLock – File encryption software that does more with less

minilock.io

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Re: MiniLock – File encryption software that does more with less

#41

Post by akerl_ »

sillysaurus3 wrote: post #38
akerl_ wrote: post #36

Earlier quoted context omitted.

No, because then the person generating their table just takes that into account. It's slighly harder, but not noticeably so compared to how secure it needs to be.

It seems like as long as the complexity of the passphrase is sufficient, then a rainbow table can't be effective. For example, a 128-bit random AES key is a kind of passphrase that's generally not susceptible to a rainbow table attack (though it's very hard for humans to remember). So the problem here is, how do you force the user to make their passphrase sufficiently complex? Passphrases also don't protect against k…

You force the password to be sufficiently complex by doing what you said: creating it (pseudo)randomly. The aforementioned 128 bit random AES key is robust, assuming the PRNG is solid. A user-provided password utilizing the human mind as its PRNG will never come close.

Re: MiniLock – File encryption software that does more with less

#42

Post by akerl_ »

MichaelGG wrote: post #40
akerl_ wrote: post #32

Earlier quoted context omitted.

Except that since there's no salt or other measures involved, there isn't even a trivial protection against rainbow tables letting me create one table and crack all the passwords. It's using ECC as a fun buzzword but tossing all the actual realworld benefits of key-pair crypto out the window by having a single user-provided string map to a single keypair.

Please enlighten us on how to generate rainbow tables for passphrases. Assuming they use a lower bound of 6 bits per character, a 100 bit phrase is 46 characters long. Off the top of my head, I'd use a book of quotations, popular lines from movies, etc. And try to hit common permutations of each. So there's a bit of low hanging fruit. But that could be detected when they generate their key. Remember, salt doesn't rea…

Assuming they were actually keeping the contents of such wordlists out and actually ensuring high-entropy passphrases, we would be in an OK place, though still far removed from the security provided by randomly seeded ECC keypairs.

But that's not the case:

https://github.com/dropbox/zxcvbn/issues/39

And as an attacker, I'm using my rainbow tables specifically to target the low hanging fruit. It gives me the best initial odds, and also the best return on any given hit: I'm way more likely to get more users per match for things in the common phrasebook, by nature of it being the common phrasebook.

Re: MiniLock – File encryption software that does more with less

#43

Post by AgentME »

sillysaurus3 wrote: post #34
diafygi wrote: post #33

Earlier quoted context omitted.

Alright, what do you propose? As I said, dealing with keyfiles is HARD for the lay-user.

What about making the user choose two passphrases, which are concatenated together by the tool? Cracking a single passphrase may be easy, but cracking two concatenated passphrases is significantly harder. E.g. password 1: "the quick brown fox jumps over the lazy dog" Password 2: "jack be nimble jack be sick" Final result, used to derive a keyfile: "the quick brown fox jumps over the lazy dogjack be nimble jack be sic…

There's no difference between that and just requiring the user to use a longer password.

Anyone trying to attack the system will just program their cracker to be more likely to try concatenating words together awkwardly in the password somewhere.

Re: MiniLock – File encryption software that does more with less

#44

Post by [deleted] »

eliteraspberrie wrote: post #27

I am not a cryptographer, but I'll offer some advice, if I may: don't let people choose a passphrase, generate one for them. People are very bad at creating good passphrases, but decent at memorizing a good one. I say that because I don't trust the zxcvbn library. It underestimates the entropy of "aaaaa" as 7 bits [log(26 * 5)], not the correct value of 23 bits [log(26) * 5], for example. In this instance, it's to yo…

[deleted]

Re: MiniLock – File encryption software that does more with less

#45

Post by Scaevolus »

infogulch wrote: post #39
Scaevolus wrote: post #14

Earlier quoted context omitted.

I've been working on generating memorable passphrases with provable entropy: http://rmmh.github.io/abbrase/ They work well for me, but some people dislike the abbreviation aspect. I'm investigating how to make a grammar-based engine (rather than bigram-based) for smaller data files and better phrases.

Nice! I like this methodology. I also wonder if all possible trigrams are equally likely. Question: why wouldn't you just use the passphrase itself as the password? Just because some websites limit password length?

The algorithm is [898, 537, 321, 205, 361] -> tidlotexidaifol -> "tidy lot existence daily following". The phrase is generated deterministically from the password, so it's no more secure than the previous steps. It's just a mnemonic to help remember the password.

If by trigram you mean "3-letter word prefix", then yes, they are all equally likely. If you mean "group of 3 words", then no, they're very biased. "raccowsli" is as likely as "afrdisuti", but it will always generate the mnemonic "race cow slipped", and never "racter cowslip slithered".

Re: MiniLock – File encryption software that does more with less

#46

Post by lolbrainwallets »

tveita wrote: post #25
Someone wrote: post #4

Earlier quoted context omitted.

I would use a secret key to encrypt the file, then encrypt the decryption key with each of the keys of those recipients, and add each (user ID, encrypted decryption key) to the file. Reading the linked page, that's exactly what they do (with a nonce to thwart various (differential, known plaintext, etc.) attacks) The header itself is a stringified JSON object which contains information necessary for the recipients to…

Exercise: This padding scheme will not hide the length of the file name as intended. Why?

AAAAAAAAAAAAAAAAA...

Re: MiniLock – File encryption software that does more with less

#47

Post by sillysaurus3 »

AgentME wrote: post #43
sillysaurus3 wrote: post #34

Earlier quoted context omitted.

What about making the user choose two passphrases, which are concatenated together by the tool? Cracking a single passphrase may be easy, but cracking two concatenated passphrases is significantly harder. E.g. password 1: "the quick brown fox jumps over the lazy dog" Password 2: "jack be nimble jack be sick" Final result, used to derive a keyfile: "the quick brown fox jumps over the lazy dogjack be nimble jack be sic…

There's no difference between that and just requiring the user to use a longer password. Anyone trying to attack the system will just program their cracker to be more likely to try concatenating words together awkwardly in the password somewhere.

It's easier for humans to remember two distinct passwords with individual complexity requirements than one gigantic passphrase.

By forcing the user to choose two passphrases which are then concatenated, the result is one gigantic passphrase that a cracker can't easily crack, yet is easy for humans to remember. It seems like this solves the problem of rainbow tables.

A keylogger could still break this system. But if an adversary has planted a keylogger, they could've simply stolen your keyfile.

Re: MiniLock – File encryption software that does more with less

#48

Post by Scaevolus »

ff7c11 wrote: post #16
Scaevolus wrote: post #14

Earlier quoted context omitted.

I've been working on generating memorable passphrases with provable entropy: http://rmmh.github.io/abbrase/ They work well for me, but some people dislike the abbreviation aspect. I'm investigating how to make a grammar-based engine (rather than bigram-based) for smaller data files and better phrases.

Oooh I like this a lot. Very clever. How many trigrams do you actually choose from?

There are 1024 trigrams, so 10 bits each. That's the same information density as random digits.

Re: MiniLock – File encryption software that does more with less

#50

Post by SomeCallMeTim »

Toad_King wrote: post #49

The overview literally just sounds like encrypted archive files. How is this different from putting a password on a .7z or .rar file?

They aren't sending the PASSWORD in the clear, they're sending (effectively) a public key.

Bob sends public key to Alice. Alice uses public key to encrypt file and sends to Bob. ONLY Bob can decrypt the file (using his PRIVATE key).

If you sent a password, then anyone who intercepted it AND the encrypted archive would be able to decrypt it.

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