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

learn more… | top users | synonyms

212
votes
12answers
33k views

How to securely hash passwords?

If I hash passwords before storing them in my database, is that sufficient to prevent them being recovered by anyone? I should point out that this relates only to retrieval directly from the ...
481
votes
23answers
88k views

XKCD #936: Short complex password, or long dictionary passphrase?

How accurate is this XKCD comic from August 10, 2011? I've always been an advocate of long rather than complex passwords, but most security people (at least the ones that I've talked to) are ...
231
votes
4answers
65k views

Do any security experts recommend bcrypt for password storage?

On the surface bcrypt, an 11 year old security algorithm designed for hashing passwords by Niels Provos and David Mazieres, which is based on the initialization function used in the NIST approved ...
158
votes
6answers
16k views

How to store salt?

Nowadays, if we expect to store user password securely, we need at least do the following thing $pwd=hash(hash($password) + salt) then store $pwd in your system instead of the real password. I have ...
53
votes
5answers
19k views

Password Hashing add salt + pepper or is salt enough?

Please Note: I'm aware that the proper method for secure password storage hashing is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. ...
236
votes
10answers
27k views

Is my developer's home-brew password security right or wrong, and why?

A developer, let's call him 'Dave', insists on using home-brew scripts for password security. See Dave's proposal below. His team spent months adopting an industry standard protocol using Bcrypt. ...
41
votes
1answer
6k views

What should end-users do about Heartbleed?

What should one do about the Heartbleed OpenSSL exploit? mainly talks about what people running websites should do about Heartbleed. What should end-users of websites be doing? Do they need to ...
244
votes
18answers
36k views

How does changing your password every 90 days increase security?

Where I work I'm forced to change my password every 90 days. This security measure has been in place in many organizations for as long as I can remember. Is there a specific security vulnerability ...
38
votes
41answers
7k views

What is your way to create good passwords that can actually be remembered?

What are the methodologies which can be used to generate "human" good quality password? They have to ensure a good strength and also easy to remember for a human being.
52
votes
12answers
8k views

How reliable is a password strength checker?

I've tested the tool from Microsoft available here which tests password strength and rates them. For a password such as "i am going to have lunch tonight", the tool rates it's strength as "BEST" and ...
28
votes
1answer
3k views

Are there more modern password hashing methods than bcrypt and scrypt?

This question made me start thinking about password hashing again. I currently use bcrypt (specifically py-bcrypt). I've heard a lot about PBKDF2, and scrypt. What I'm wondering is if there are any ...
19
votes
4answers
2k views

Why is using salt more secure?

Storing the hash of users' passwords, e.g. in a database, is insecure since human passwords are vulnerable to dictionary attacks. Everyone suggests that this is mitigated via the use of salts, but the ...
14
votes
2answers
641 views

Is it a bad idea for an information holder to e-mail a user their password?

A couple of websites with which I'm registered have, after a period of inactivity on my part, each sent me an e-mail to remind me that I'm still registered. In each case, that e-mail has included my ...
52
votes
4answers
10k views

Recommended # of iterations when using PKBDF2-SHA256?

I'm curious if anyone has any advice or points of reference when it comes to determining how many iterations is 'good enough' when using PBKDF2 (specifically with SHA-256). Certainly, 'good enough' is ...
21
votes
4answers
2k views

What should be used as a salt?

I always hear that it is best to use salts on top of stored passwords, which then somehow gets concatenated and hashed afterwards. But I don't know what to use as a the salt. What would be a good ...
19
votes
5answers
2k views

Security impact of using a public password for free WiFi

We have a WiFi network that we want to be public and free. Does having a password that is known to everyone provide any additional security advantage to the people using this network as opposed to ...
50
votes
5answers
10k views

Is sending password to user email secure?

How secure is sending passwords through email to a user, since email isn't secured by HTTPS. What is the best way to secure it? Should i use encryption?
64
votes
13answers
12k views

Why do sites implement locking after 3 failed password attempts?

I know the reasoning behind not letting infinite password attempts -- brute force attempts is not a meatspace weakness, but a problem with computer security -- but where did they get the number 3 ...
30
votes
5answers
4k views

How do some sites (e.g. online banks) only ask for specific characters from a password without storing it as plaintext?

I thought How can a system enforce a minimum number of changed characters... would answer my question, but it seems this is a different case. When I sign on to my online banking account, I'm prompted ...
25
votes
9answers
10k views

Feeding /dev/random entropy pool?

Which way of additionally feeding /dev/random entropy pool would you suggest for producing random passwords? Or, is there maybe a better way to locally create fully random passwords?
45
votes
7answers
2k views

Is it OK to tell your password to your company's sysadmin?

I'm working in a small company (20 employees) as a senior software engineer. After having problems with my email, our newly employed IT administrator asked me to write my user password to someone in ...
24
votes
5answers
2k views

How valuable is secrecy of an algorithm?

On the surface, the inadvisability of security through obscurity is directly at odds with the concept of shared secrets (i.e. "passwords"). Which is to say: if secrecy around passwords is valuable, ...
11
votes
3answers
3k views

How can I prevent someone from accessing a Windows XP system via boot disk?

Apparently a computer system protected by a a login password, e.g. Windows XP, can be easily hacked by someone with physical access to it using methods like this one: ...
27
votes
8answers
2k views

Is there a method of generating site-specific passwords which can be executed in my own head?

I was thinking recently about password security. My goal is to have mostly random passwords, that are different for each site. But you also should be able to remember them (or re-generate them) ...
21
votes
3answers
2k views

Is there any advantage to splitting a password?

I've been reading about the LANMAN (LM) hash and I'm curious about a particular part of the algorithm. The LM hash is computed as follows: The user’s ASCII password is converted to uppercase. ...
34
votes
2answers
3k views

Pre-hash password before applying bcrypt to avoid restricting password length

Good practice is not to unnecessarily restrict password length, so that appropriately-long passphrases (perhaps 35-45 chars for 6/7 dicewords) can be used. (See e.g. Should I have a maximum password ...
26
votes
8answers
3k 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 ...
31
votes
9answers
7k views

How long should the password be?

The minimum password length recommended is about 8 characters, so is there any standard/recommended maximum length of the password?
16
votes
4answers
5k views

Google Account: implications of using application-specific passwords

In the wake of the recent Mat Honan story I decided to try out two-factor authentication on my Google account. But in order to keep using it with Exchange, the Android OS, Google Talk and Google ...
12
votes
6answers
6k 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 ...
8
votes
4answers
3k views

What is a good practical (and sane) way to manage all your passwords for online sites?

I am just a mere mortal that wants to have a somewhat secure way of managing all my passwords. This is something that I have been putting off, but since LinkedIn decided to give away one of my ...
18
votes
5answers
3k 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. ...
17
votes
3answers
2k 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 ...
280
votes
13answers
45k views

What technical reasons are there to have low maximum password lengths?

I have always wondered why so many websites have very firm restrictions on password length (exactly 8 characters, up to 8 characters, etc). These tend to be banks or other sites I actually care about ...
43
votes
8answers
65k 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 ...
160
votes
17answers
10k views

Passwords Being Sent in Clear Text Due to Users' Mistake in Typing it in the Username Field

Upon reviewing the Logs generated by different SIEMs (Splunk, HP Logger Trial and the AlienVault platform’s SIEM) I noticed that for some reason quite a few users tend to make the mistake of typing ...
52
votes
7answers
26k 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 ...
24
votes
2answers
5k views

I just send username and password over https. Is this ok?

When a user's logging in to my site, they send their username and password to me over https. Besides the ssl, there's no special obfuscation of the password - it lives in memory in the browser in the ...
41
votes
5answers
2k 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 ...
41
votes
11answers
6k views

What to do about websites that store plain text passwords

I recently received an email from a popular graduate job web site (prospects.ac.uk) that I haven't used in a while suggesting I use a new feature. It contained both my username and password in plain ...
21
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 ...
15
votes
2answers
3k 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 ...
32
votes
3answers
1k 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 ...
22
votes
4answers
3k 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?
8
votes
4answers
707 views

Calculating how secure my password is

I generally use gnuPG for encrypting my files. And as far as I know it's strength ultimately depends on the passphrase I use. So, I would like to know: how can I mathematically calculate how secure my ...
5
votes
2answers
2k 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 ...
21
votes
5answers
2k views

Is my bank storing my password in plain text?

My bank (and every bank I've come across) only ever asks for individual characters from my password when logging in. Is my bank storing my password in plain text?
20
votes
4answers
1k 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 ...
19
votes
5answers
2k 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 ...
4
votes
2answers
3k 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 _). ...