Specific to the security of passwords: hashing, entropy, cracking, resets, lockouts, etc.

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17
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6answers
5k views

Managing website passwords for small team

I'm part of a small group of people who manage a website and the server it runs on. We have many accounts with third-party websites or services that multiple people on the team need to access. What is ...
10
votes
5answers
2k views

Is including a secret GUID in an URL Security Through Obscurity?

I know that this question is a little bit on the side of Opinion/Discussion, but I think there's a provable answer to it. I think the common view of "Security Through Obscurity" is that the security ...
5
votes
2answers
3k views

Reference implementation of C# password hashing and verification

Does anyone have a reference implementation (ideally 3rd party certified, or government approved) way one-way hash a password for C# and or Java? Ideally,I'd like to see something that includes a ...
30
votes
8answers
5k views

Do non-keyboard characters make my password less susceptible to brute forcing?

I can put characters in my password for which there are no keys on a keyboard. On Windows, Alt+#### (with the numpad) inserts the character for whatever code you type in. When I put this in a ...
21
votes
5answers
5k views

What's the practical limit for rainbow-table based bruteforce?

Say we have a hash of a password. The password can be considered to be made of of totally random characters and has a fixed length of N. The hash is SHA1(password+salt), where the salt is of length M. ...
22
votes
5answers
2k views

When hashing passwords, is it ok to use the hashed password as the salt?

I don't like this idea. But I can not come up with a technical argument against it. Can somebody explain it to me? The basic idea is: $passwd = 'foo'; $salt = hash($passwd); $finalHash = hash($passwd ...
16
votes
6answers
2k views

Are password complexity rules counterproductive?

In creating a login for this site I chose a nondictionary password that would be extremely hard to guess, but easy to remember. I was told that it did not meet complexity rules. After several ...
10
votes
2answers
1k views

What is the purpose of a Pepper?

I've been trying to find out exactly what a pepper is. The only things I could accurately determine are that a Pepper: Is theoretically unique from site to site and hard-coded in the site's source ...
333
votes
13answers
66k views

Are passwords stored in memory safe?

I just realized that, in any language, when you save a password in a variable, it is stored as plain text in the memory. I think the OS does its job and forbids processes from accessing each other's ...
60
votes
2answers
70k views

How difficult to crack keepass master password?

How easily could someone crack my keepass .kdbx file if that person steals the file but never obtains the Master Password? Is this a serious threat, or would a brute force attack require massive ...
29
votes
8answers
5k views

Why would salt not have prevented LinkedIn passwords from getting cracked?

In this interview posted on Krebs on Security, this question was asked and answered: BK: I’ve heard people say, you know this probably would not have happened if LinkedIn and others had salted ...
32
votes
2answers
13k views

HMAC - Why not HMAC for password storage?

Nota bene: I'm aware that the good answer to secure password storage is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. Let's say ...
45
votes
5answers
10k views

Are GUIDs safe for one-time tokens?

I see a lot of sites use GUIDs for password resets, unsubscribe requests and other forms of unique identification. Presumably they are appealing because they are easy to generate, unique, ...
13
votes
6answers
8k views

Is PBKDF2-based System.Cryptology.RFC2898DeriveBytes() “better” for Unicode Password hashing than traditional methods?

When is it appropriate to use RFC2898DeriveBytes versus a typical hash? Update I now understand that a KDF is typically used to create a symmetric key for possible use in encrypting a stream. I ...
6
votes
3answers
24k views

Windows 7 Password Hash Security

I recently came across a number of sources that suggest that cracking Windows user account passwords is easy by examining their password hashes. I understand that these hashes are stored in the SAM ...
20
votes
3answers
3k views

Should I have a maximum password length?

I'm creating a webapp, and part of my authentication method is password length. Should I put one in place? (say, 50 characters?) Or should I just put a minimum length (Currently at 6). Are there ...
14
votes
5answers
10k views

How can I avoid putting the database password in a perl script?

I have a cronned perl script that connects to our database and does various kinds of lookups and integrity checks. The original script was written by someone long ago. My job is to make some changes ...
3
votes
4answers
1k views

Best practice for forgot password form, ok to leak that a given e-mail is invalid

On our forgot password reset form, is it ok to leak that a given e-mail address entered is invalid? Or should we always just return success and check your e-mail, even if the e-mail is not valid. I ...
7
votes
1answer
765 views

Password Managers: encrypted database vs hashing strategy

I'm considering moving to a password-management strategy based on supergenpass or something similar. This is an alternative to other password managers where instead of having a database of passwords ...
3
votes
6answers
1k views

“Double hashing” with 2 different hash functions

Is doing something like this sha256(sha512(password+salt)) Less secure then just doing sha256(password+salt) I've heard it will increase collision chances. I can think of 3 reasons to do this ...
90
votes
9answers
173k views

Where can I find good dictionaries for dictionary attacks?

I’m wondering where I can find good collections of dictionaries which can be used for dictionary attacks? I've found some through Google, but I’m interested in hearing about where you get your ...
147
votes
9answers
31k views

Is “the oft-cited XKCD scheme […] no longer good advice”?

I was stumbling around and happened onto this essay by Bruce Schneier claiming that the XKCD password scheme was effectively dead. Modern password crackers combine different words from their ...
67
votes
7answers
66k views

Certificate based authentication vs Username and Password authentication

What are the advantages and drawbacks of the certificate based authentication over username and password authentication? I know some, but I would appreciate a structured and detailed answer. UPDATE ...
92
votes
3answers
32k views

How does Google Authenticator work?

Google Authenticator is an alternative to SMS for 2Step verification, installing an app on Android where the codes will be sent. It works without any connectivity; it even works on plane mode. This ...
11
votes
2answers
15k views

openssl: recover key and IV by passphrase

A large amount of files were encrypted by openssl enc -aes-256-cbc -pass pass:MYPASSWORD Openssl should derive key+IV from passphrase. I'd like to know key+IV equivalent of that MYPASSWORD. Is ...
32
votes
6answers
28k views

Is saving passwords in Chrome as safe as using LastPass if you leave it signed in?

Justin Schuh defended Google's reasoning in the wake of this post detailing the "discovery" (sic) that passwords saved in the Chrome password manager can be viewed in plaintext. Let me just directly ...
19
votes
1answer
5k views

How to apply a pepper correctly to bcrypt?

Update: There is a better way to add a server side key, than using it as a pepper. With a pepper an attacker must gain additional privileges on the server to get the key. The same advantage we get ...
33
votes
4answers
21k views

Standards for encrypting passwords in configuration files?

My workplace has a standard that plaintext passwords are not allowed in application configuration files. This makes enough sense on its face, in case someone gets access to the config files they ...
48
votes
7answers
3k views

Do security questions subvert passwords?

Do security questions subvert hard to crack passwords? For example, if a site requires passwords with a certain scheme (length + required character sets) and has a security question, why would someone ...
19
votes
3answers
3k views

Is a password in the clipboard vulnerable to attacks?

I see situations where you may have to input the same password more than once. You may type it in a text editor and copy it to clipboard, to paste it two or more times. In what scenarios this could ...
28
votes
5answers
4k views

Is it common practice to log rejected passwords?

While selecting unique passwords for each purpose is a great idea, in practice this rarely happens. Therefore many select passwords from a personal pool of passwords that are easily remembered. When ...
22
votes
13answers
4k views

Why do we even use passwords / passphrases next to biometrics?

In the last couple of days there were a lot of talking about passwords and passphrases, not only here, but on several blogs and forums I follow (especially after XKCD #936 saw the light of this ...
22
votes
3answers
2k views

Does overlaying the mouse on a virtual numeric keyboard really protect against keyloggers?

I just saw for the first time a new way to enter a password, at the Banque Postale (French Bank). You are given a virtual numeric keyboard and to type you can just leave the mouse cursor over a number ...
20
votes
1answer
7k views

Can a dictionary attack crack a Diceware passphrase?

Everyone knows the words used in Diceware passwords (all 6^5 = 7776 words are published) -- they're all common words. Everyone seems to know that we're not supposed to use dictionary words for ...
19
votes
2answers
5k views

Why is it always `HASH( salt + password )` that we recommend?

Browsing over this site, many forums, online articles, there's always one specific way we're suggesting to store a password hash: function (salt, pass) { return ( StrongHash(salt + pass) ) } But ...
29
votes
4answers
7k views

How secure are my passwords in the hands of Firefox using a Master Password?

I'm relying on Firefox to remember my passwords, using a Master Password of more than 25 characters. How secure is this set-up?
36
votes
3answers
2k views

Am I wrong to believe that passwords should never be recoverable (one way hash)?

I recently forgot my password for our cable provider online account, only to discover that they sent it to us via plain text in an email. I quickly sent an email to customer support asking them if ...
11
votes
3answers
964 views

Calculating how secure my password is

I generally use GnuPG for encrypting my files and as far as I know its strength ultimately depends on the passphrase I use. So, I would like to know: how can I mathematically calculate how secure my ...
8
votes
4answers
810 views

Doesn't imposing a minimum password length make the password weaker by reducing the number of possible combinations?

I thought the strength of a password depended on the total number of possible combinations. Therefore, allowing longer passwords should be safer because you then have more possibilities. But why do ...
19
votes
4answers
4k views

The registration confirmation email contains my password: do they keep it in plaintext?

I was kind of shocked when I just received my confirmation mail from the shop where I just registered myself: they sent my username (which is my email address) and the password I typed in. The ...
18
votes
6answers
1k views

Appropriate password requirements for a login (OpenID) service/provider/delegate/thing

This is with regards* to Stack Exchange's upcoming OpenID provider (and in particular, discussion about password requirements). Currently, password requirements are: Must contain 3 of: lower case ...
15
votes
5answers
1k views

Is it legal to log passwords from failed logins?

Is it legal to store/log mistyped passwords? How many of you have seen this happen in a log file or DB?
8
votes
2answers
2k views

Does bcrypt compare the hashes in “length-constant” time?

I saw this function slowEquals() while reading Salted Password Hashing - Doing it Right, which uses a byte-level xor comparison to avoid timing attacks. I was wondering whether this is what Bcrypt ...
7
votes
2answers
6k views

How expensive is it to guess a 15 character password, and should I be worried?

I'm currently using AES encryption (at home) on GNU/Linux (one of LUKS AES-256 variants with xts) and on Windows 7 (Truecrypt) with a 15 characters password (alphanumeric lowercase only plus _). ...
7
votes
2answers
372 views

Is cascading cryptographic algorithm better than using a single one?

Am I wrong to think that scrypt(bcrypt(password)) would be better than using sole (s|b)crypt? Especially when considering two different key for the two algorithms. I am also interested in some ...
7
votes
2answers
2k views

How often should passwords change?

I'm asking two very related questions As an admin what policies should be enforced regarding the frequency of password changing? I have an idea that users should be forced to change their ...
9
votes
1answer
989 views

Would it make sense to use Bcrypt and PBKDF2 together?

I've read various opinions about whether Bcrypt or PDBKF2 is a better key derivation hashing method. The answer seems to depend on a lot of complicated factors that are not easy to analyze. Would ...
2
votes
5answers
737 views

passphrases - lowercase and dictionary words

Amid all the discussion about password length vs. complexity (summarized by the famous xkcd strip and the followup dicussion) I am trying to make up my mind about passphrases made up with dictionnary ...
152
votes
18answers
16k views

What is a good analogy to explain to a layman why passwords should be hashed?

Note: This is not an actual situation I'm currently in. Assume your boss is one of those old-fashioned computer-illiterate managers and wants to store the passwords in plaintext to simplify ...
83
votes
11answers
15k views

Password rules: Should I disallow “leetspeak” dictionary passwords like XKCD's Tr0ub4dor&3

TLDR: We already require two-factor authentication for some users. I'm hashing, salting, and doing things to encourage long passphrases. I'm not interested in the merits of password complexity rules ...