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80

Salted hashes are designed to protect against attackers being able to attack multiple hashes simultaneously or build rainbow tables of pre-calculated hash values. That is all. They do nothing to improve the underlying strength of the password itself, weak or strong. This also means that they're not designed to defend against online attacks, so they ...


38

Getting salt from hash(salt+password) would be just as difficult as getting password from hash(salt+password).


34

You have to consider two attack vectors: Online attack Offline attack Limiting login guessing helps against Online attacks. Let's say it's three times, this means that an attacker can test ALL accounts for the three most common passwords that fit your password policy (how about "password", "12345678" and "12345"?). Salting helps against Offline attacks ...


32

The long password recommendation is to protect passwords from being cracked if someone has access to the hash of that password. Tools like hashcat can easily (using gpu) test 93800M c/s md5 hashes As a user usually you don't know how does the site stores your password so it is better to use a long password to mitigate those attacks.


29

The following doesn't really do this justice, but in summary... In an ideal world no, complicated passwords should not be required for online resources. But, in that ideal world we are dependent on the administrators of the system to harden systems to prevent unauthorised access to the 'password file', the following will minimise the risk: Securely ...


29

Picking good passwords is hard. Humans and our penchant for patterns simply aren't very good at it. Multiply that by the dozens of accounts we accumulate over time, and this is the root of the problem. So yes, eliminating bad passwords and password reuse can solve the problem of creating soft targets, but it doesn't solve the root problem of ...


23

The most significant potential risk that I see is that profile information on these sorts of sites could potentially be quite useful for pivoting into identity theft. If there is stored financial information visible (like the last four digits of your credit card number, for instance) this has been shown to be useful in helping attackers own additional ...


18

You cannot reasonably prevent "sequence passwords" unless you have a human administrator inspect them (which would have its own set of security issues, not even considering the expensiveness of human labour). You can try to automatically detect such patterns, but you cannot hope to find them all; besides, if you only keep hashes of the previous passwords, ...


17

You use distinct passwords on distinct systems because you know that some of these passwords may leak. If your passwords are high enough in entropy then they won't leak through brute force, but they may still leak through some other ways, e.g. server compromise (grabs the passwords as they come by), key loggers (grabs the password as it is typed),... Using ...


17

"assume that this isn't a malicious hacker" right... If you are okay with your name, account number, home address and account details being sold or used as part of a social engineering attack on you then there is no more need to protect it than your Facebook account. However most people think this is enough of a reason to not set their password to ...


14

This basically looks like something along the lines of PBKDF2 or sha512crypt, only with a bunch of "cryptographic voodoo" applied. Salts have a very specific cryptographic purpose: to tie an password-guessing attempt to a single password instance. Having company-specific salts, user-specific salts, per-iteration salts, and (to steal a snark) hand-harvested, ...


13

Usually, the password isn't stored in the cookie. You login to example.com with your username and password, these are verified to belong to you (typically by hashing your password and checking the hash of your password matches with the hash for a user with that username), and the server issues you a long random number token as a secret identifier for you. ...


12

I'm not really sure why you would want to find the salt, since generally the salt is not considered secret. Basically in your case the salt is essentially the password as you do not know what it is and the password is your salt (let's take semantics aside that dictates as the password will probably not be globally unique) as it's not secret. The PBKDF2 ...


10

The only sane assumptions for any web developers using local password authentication are: that their users are going to be using the same password for everything; that the site has already been compromised, even if they haven't finished writing it yet; and there will be some really expensive legal liability attached to the consequences of that compromise. ...


9

In general, attackers are adaptive. They know what people think. If users tend to begin their passwords with 'z' then attackers will start their brute force with that letter. Any specific strategy, such as choosing a 'z' as first letter, may give you an edge over the attacker only as long as the attacker does not know it; so talking about it on a public ...


9

In a perfect world, sure that would be a wonderful method for a human to remember their passwords. However, the world is far from perfect. The main issue with your method is that if just one of your passwords is ever discovered (through leakages, guesses, breaches, etc) then your entire security apparatus could unravel -because patterns are trivial to ...


8

Pronounceable words are more-or-less sequences of syllables. What constitutes a syllable depends on the language, including the language variant (British, Scottish, American, Indian... versions of English are not rigorously identical). So we will make some approximations. Let's suppose that we want two-letter syllables, always a consonant followed by a ...


7

Salting/hashing is great if your database gets stolen, but it has nothing to do with dictionary attacks that might take place through the normal login procedure. As you mentioned limiting the number login attempts and using CAPTCHA can make dictionary attacks that take place through the normal login procedure ineffective, but salting (or not) won't have ...


7

If you assume the attacker has the file, then you're actually relying on the number N as your password. You have stated that this is a user selected number, and it's likely that users would just chose (for example) 111....111, 123..., 000...000, or something similar. This could be countered by telling the user what value of N to use at "generation time", ...


7

There are a few different ways to check whether users' old and new passwords are similar, and each has its own strengths and weaknesses. String Permutation Comparison The first approach relies on creating a list of permutations that are not allowed. This might be a list of regular expressions or some similarly defined string changes that you evaluate ...


6

You don't get a weak password out of a strong scheme, because there is no such thing as password strength. Sometimes we say "this password is weak", but what we really mean (that is, if the "we" that is speaking knows what he is talking about) is that "this password generation method is weak". The important point here is that password security, just like ...


6

If we want to look for rational reasons not to use scrypt right now, we can find mostly these three: It is unclear whether a "memory-hard" function is what is needed, with the parameter configurations supported by scrypt. Scrypt was initially designed to support local encryption, particularly whole-system encryption. This means that the password must be ...


6

Assuming you know the hash function and method used to generate the hash from the password and salt it is possible to discover the salt if you have the original password and the end hash. It would be using brute force - there's no clever or quick way to do it. In your typical scenario your hash is generated by 1) hashing the password then 2) combining it ...


5

"MD5(SHA-1(password))" is more secure than "MD5(password)" in the following sense: computing SHA-1 then MD5 on a candidate password takes about 2.5x the time it takes to compute only MD5 on the same password. Thus, it makes naive dictionary attacks 2.5x slower. It still is pathetically weak, for two reasons: 2.5x slower than a single MD5 is still awfully ...


5

This provides almost no additional security over using the same password everywhere. The entire point of using multiple passwords is to prevent a leak of one from compromising multiple accounts. If I get your password to twitter, the first thing I'm going to do trying to hack you on Google is going to be to try permutations of your twitter password. It ...


5

To expand further on these answers, only you can say if it's "worth it." The heart of this question has to do with risk analysis. Best practice would typically state that for any account like this you should have a randomly generated password stored in a password manager. Typically most find the amount of work necessary to do this is much smaller in relation ...


5

No. The "random art" image is created by a random walk through the image area, using the key's fingerprint as the sequence of moves to make. The fingerprint is short enough that the art can never cover more than about 40% of the image. An analysis of the art and some attempts at attacks on it are available in the paper "The Drunken Bishop".


4

No, one point of salted hashing is to get good randomness in the hash regardless of the starting material. However, this does not free us to use bad passwords. Good hashing only protects against one attack vector: that where the intruder steals the file with the hashes. So many other attack vectors on passwords exist... shoulder surfing, brute forcing, ...


4

First, most tools/websites like "HowSecureIsMyPassword" do not only consider bruteforce attacks but also dictionary and rainbow attacks, as well as simple rules such as password length, character pool, use of words, etc. Hence passwords like aaaaaaa and ZZZZZZZ, will most of the time be evaluated the same way. To the best of my knowledge, there is no ...


4

No, it does not mean they are storing the passwords in plain text. The question doesn't completely describe the behavior. Are they matching patterns only from your current password, or patterns from all 8 of your previous passwords? If it's the first case, the answer is dead simple, and this is that they have the hashes from the 8 previous passwords ...



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