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Evernote hacked

blog.evernote.com

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Re: Evernote hacked

#191

Post by wsargent »

jgrahamc wrote: post #36
UnoriginalGuy wrote: post #11

The following blog post is also being sent to all Evernote users as an email communication. Evernote’s Operations & Security team has discovered and blocked suspicious activity on the Evernote network that appears to have been a coordinated attempt to access secure areas of the Evernote Service. As a precaution to protect your data, we have decided to implement a password reset. Please read below for details and inst…

Even though this information was accessed, the passwords stored by Evernote are protected by one-way encryption. (In technical terms, they are hashed and salted.( http://en.wikipedia.org/wiki/Salt_(cryptography) )) That's great. But to really reassure people they would do best to reveal the algorithm. After all, DES-based password hashes are both 'hashed and salted' but are easily broken with JtR.

It's MD5 with a salt.

"Since the hashed password is never exposed outside of our data center, we don’t think that the differences between MD5 and SHA-1 are relevant. I.e. the risks for MD5 are about producing two inputs that match the same output. In the case of a purely back-end MD5 hash, any hypothetical attacker doesn’t have access to either the output (the MD5 hash) or the original input (the user’s password and our salt), so there really isn’t any productive attack based on MD5 vulnerabilities.

Of course, if someone has your original password and our salt, they might be able to come up with a SECOND synthetic password that hashes to the same value. (Since we constrain password characters that we accept, that might not be possible, but let’s assume it is…) The attacker could theoretically use this second password to access your account. But that same attacker could just use your original password, so I don’t see a real-world attack that would be improved with SHA1.

(Before Evernote, I spent five years building high-end cryptographic systems for government customers [e.g. http://www.isto.org/ose-site/file-fix/Public/corestreet-secu..., so I get to make use of my old crypto knowledge from time to time…)"

http://blog.evernote.com/tech/2011/05/17/architectural-diges...

Re: Evernote hacked

#192

Post by floody-berry »

UnoriginalGuy wrote: post #41
[deleted] wrote: post #22

Earlier quoted context omitted.

[deleted]

An oxymoron is two words which mean the opposite but yet the two combined words form a new expression which remains "true." For example "bitter sweet." Bitter and sweet mean two different opposite things, but the two words together are "true" because something can be both bitter and sweet. Encryption means simply to convert information into a form which cannot be easily read by an unauthorised party. One way or lossy…

Encryption implies that an authorized party can also decrypt/read the encrypted data. In that sense, "one way" + "encryption" is an oxymoron.

Further, "one way encryption" appears to only exist so nobody has to explain to regular users (and a lot of developers apparently) what is actually being done with their passwords.

Re: Evernote hacked

#193

Post by hdra »

Terretta wrote: post #109
UnoriginalGuy wrote: post #11

The following blog post is also being sent to all Evernote users as an email communication. Evernote’s Operations & Security team has discovered and blocked suspicious activity on the Evernote network that appears to have been a coordinated attempt to access secure areas of the Evernote Service. As a precaution to protect your data, we have decided to implement a password reset. Please read below for details and inst…

Your blog post says: > "Avoid using simple passwords based on dictionary words" And yet your password algorithm rejects highly secure pass phrases: > "New passwords can contain letters, numbers and punctuation." Disallowing spaces is particularly annoying for a company with a strong security requirement, as passphrases are simultaneously far more secure and far more memorable than the monkey rules your validation dem…

seriously though, its 2013, is there any reason to enforce character sets allowed in a password? I should be able to use any kind of character i want.

Re: Evernote hacked

#194

Post by m8urn »

Niten wrote: post #122
Terretta wrote: post #109

Earlier quoted context omitted.

Your blog post says: > "Avoid using simple passwords based on dictionary words" And yet your password algorithm rejects highly secure pass phrases: > "New passwords can contain letters, numbers and punctuation." Disallowing spaces is particularly annoying for a company with a strong security requirement, as passphrases are simultaneously far more secure and far more memorable than the monkey rules your validation dem…

Anyone using this comic to imply that a passphrase is more secure than a short random password hasn't done the math. This is comparing a passphrase drawn from four of the 2048 most common words against not a random password, but one based on a mutated version of one of the 65536 most common words. The example passphrase does have the equivalent of 44 bits of entropy: log_2 (2048^4) = 4 * 11 = 44 However, if we take a…

The problem with your argument is that you are equating entropy with password strength. While entropy is a valid measurement of password randomness, it is not a direct measurement of how strong a password is. Take the password "vvvvvv.vvvvvvvvvv7vvvvvv" which has terrible entropy yet is very unlikely to be cracked. Why? because a cracker does not know that your password contains only three distinct characters and would still perform a brute force attack based on an assumption of higher entropy.

If you are talking about short passwords, entropy is critical in determining the strength of the password, but the true measure of a password's strength is the permutations required to perform a brute force attack. While range of character sets determine permutations, so does the password length. You can make up for one with the other, which is why "vvvvvv.vvvvvvvvvv7vvvvvv" is a very secure password.

That aside, I did address more of the math of the XKCD comic here: http://xato.net/passwords/analyzing-the-xkcd-comic/

Re: Evernote hacked

#195

Post by Volpe »

Terretta wrote: post #170
Niten wrote: post #162

Earlier quoted context omitted.

Respectfully, you are flat out wrong. This "entropy check" doesn't prove what you think it does. This password strength test is attempting to estimate the entropy of given passwords under the assumption that it is a word roughly obeying the character distributions of English text, using Shannon's approximation. It does not apply to randomly generated passwords, which violate these assumptions, as described in Appende…

First, all this is beside the point. Evernote hasn't understood the concepts of either entropy or human chosen passwords. Rejecting my passphrase and accepting "abc123" is wrong . That's my original post, and that's what you objected to. Computer generated random passwords that nobody's going to use on their mobile phone Evernote client, simply don't figure into normal human use. Our job is to recommend things that c…

While "This phrase is definitely not in the dictionary" is true, every component is. If this sort of password became popular brute forcing passwords would just start using whole word combinations when cracking passwords. i.e a word becomes the equivalent of a character (though from a larger set of characters).

Also wouldn't a hash of a long passphrase be longer? (I am completely ignorant the details of hashing algorithms)... so if I'm cracking a table of hashed passwords, I could set a "passphrase" cracker on hashed passwords of above average length?

Re: Evernote hacked

#196

Post by benaiah »

Joeri wrote: post #140
sdevlin wrote: post #105

Earlier quoted context omitted.

If this were true, there would be no reason to hash passwords. There are hashing algorithms (bcrypt, scrypt, PBKDF2) that are specifically designed to be slow to prevent these attacks.

PBKDF2 is not memory hard, so even with known technology it can be broken relatively easy. Bcrypt seems secure for now, but you shouldn't rely on security through obscurity, which is essentially what putting faith in the irreversability of a hash is. The reality is that if a hashed password leaks, you should assume it will be broken. It's like with bank vaults. They're not designed to withstand attack, just to delay…

Hashes are mathematically proven to be irreversible except through rainbow tables (easily beaten with salting) or brute force. There's no faith needed (well, I suppose that non-mathematicians like myself have to put faith in the math, but I trust the hundreds of independent studies of these algorithms quite well), and it's not anything close to "security through obscurity".

That said, you are right. You should always change passwords that are leaked. This, however, is due to the poor security practices of most companies, not some bizarre distrust of hashes.

Re: Evernote hacked

#197

Post by benaiah »

floody-berry wrote: post #192
UnoriginalGuy wrote: post #41

Earlier quoted context omitted.

An oxymoron is two words which mean the opposite but yet the two combined words form a new expression which remains "true." For example "bitter sweet." Bitter and sweet mean two different opposite things, but the two words together are "true" because something can be both bitter and sweet. Encryption means simply to convert information into a form which cannot be easily read by an unauthorised party. One way or lossy…

Encryption implies that an authorized party can also decrypt/read the encrypted data. In that sense, "one way" + "encryption" is an oxymoron. Further, "one way encryption" appears to only exist so nobody has to explain to regular users (and a lot of developers apparently) what is actually being done with their passwords.

"One way encryption" == hashing. Maybe not the best term, but it's pretty obvious what they mean.

Re: Evernote hacked

#198

Post by rorrr »

luser001 wrote: post #169
miles wrote: post #166

Earlier quoted context omitted.

Thanks for igniting this discussion, Niten. While digging around, I stumbled onto this tool which others might find helpful: https://github.com/lowe/zxcvbn zxcvbn, named after a crappy password, is a JavaScript password strength estimation library. Use it to implement a custom strength bar on a signup form near you! zxcvbn attempts to give sound password advice through pattern matching and conservative entropy calcul…

Pretty cool tool! My passphrases (omitting spaces between words) get a score of 2. But if I drop the vowels, the score goes to 4 and crack time to 'centuries'. I wonder if this is a good way to create passphrases. Anybody want to chime in?

Don't use phrases. Use one really strong password that you can remember with a tool like KeePass. Generate random long passwords (30 characters) for everything and store them in KeePass.

I've recently converted all my accounts to that - my passwords are practically unbreakable, at least with the current tech. I feel way more secure than with the shit I had to memorize before.

Re: Evernote hacked

#199

Post by rudedogg »

Volpe wrote: post #195
Terretta wrote: post #170

Earlier quoted context omitted.

First, all this is beside the point. Evernote hasn't understood the concepts of either entropy or human chosen passwords. Rejecting my passphrase and accepting "abc123" is wrong . That's my original post, and that's what you objected to. Computer generated random passwords that nobody's going to use on their mobile phone Evernote client, simply don't figure into normal human use. Our job is to recommend things that c…

While "This phrase is definitely not in the dictionary" is true, every component is. If this sort of password became popular brute forcing passwords would just start using whole word combinations when cracking passwords. i.e a word becomes the equivalent of a character (though from a larger set of characters). Also wouldn't a hash of a long passphrase be longer? (I am completely ignorant the details of hashing algori…

No, the hash is always the same length, a single character and a 4GB movie will generate a hash of the same length (using the same hash algorithm (md5, sha512, etc). I've casually read about it, I think that is the point of the hash, to take an input of any size or length and represent it as a fixed size.

The problem with this is hash collisions, weaknesses found in hash algorithms can make it so attackers could generate files to match another files hash (or password or w/e). I think the idea is that they create a harmful file, then add null characters or w/e so the hash algorithm will generate/assign the two different files the same hash.

Re: Evernote hacked

#200

Post by cynwoody »

miles wrote: post #166
Niten wrote: post #122

Earlier quoted context omitted.

Anyone using this comic to imply that a passphrase is more secure than a short random password hasn't done the math. This is comparing a passphrase drawn from four of the 2048 most common words against not a random password, but one based on a mutated version of one of the 65536 most common words. The example passphrase does have the equivalent of 44 bits of entropy: log_2 (2048^4) = 4 * 11 = 44 However, if we take a…

Thanks for igniting this discussion, Niten. While digging around, I stumbled onto this tool which others might find helpful: https://github.com/lowe/zxcvbn zxcvbn, named after a crappy password, is a JavaScript password strength estimation library. Use it to implement a custom strength bar on a signup form near you! zxcvbn attempts to give sound password advice through pattern matching and conservative entropy calcul…

Interesting.

xyzzy scores 'instant'.

My B of A pass phrase, Jer1m1ah Cl4rke, scores 31 years. Should I change it?

https://dl.dropbox.com/u/209/zxcvbn/test/index.html

Edit: I just checked 9223372036854775808L, and it answered 'centuries' with a suspiciously round crack time in seconds. Don't think so.

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