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

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534
votes
22answers
101k 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 ...
301
votes
12answers
48k 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 ...
271
votes
13answers
54k 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 ...
270
votes
19answers
42k 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 ...
254
votes
4answers
73k 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 ...
248
votes
10answers
28k 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. ...
242
votes
12answers
40k 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 ...
175
votes
6answers
20k 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 ...
169
votes
17answers
11k 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 ...
168
votes
7answers
36k views

Why would you not permit Q or Z in passwords?

Jetblue's password requirements specify that, among other stringent requirements: Cannot contain a Q or Z I can't fathom a logical reason for this, unless it were say, extremely common for the ...
131
votes
18answers
13k 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 ...
121
votes
9answers
21k 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 ...
121
votes
8answers
9k views

Why are salted hashes more secure?

I know there are many discussions on salted hashes, and I understand that the purpose is to make it impossible to build a rainbow table of all possible hashes (generally up to 7 characters). My ...
114
votes
5answers
11k views

Does Facebook store plain-text passwords?

I was about to reset my Facebook password and got this error: Your new password is too similar to your current password. Please try another password. I assumed that Facebook stores only password ...
74
votes
11answers
8k views

“Username and/or Password Invalid” - Why do websites show this kind of message instead of informing the user which one was wrong?

Lets say a user is logging into a typical site, entering their username and password, and they mistype one of their inputs. I have noticed that most, if not all, sites show the same message (something ...
74
votes
8answers
7k views

Why not allow spaces in a password?

"Your password can't contain spaces." is a message I see from some websites, including 1 . Why? (This question is very similar to Why Not Allow Special Characters In a Password? , but the answers ...
70
votes
8answers
9k views

Convincing my manager to use salts

My manager says we don't need to salt our passwords because people are not likely to use the same password because they all have different native languages, in addition to the websites they are active ...
67
votes
13answers
6k views

VP of IT claims he unhashed 100% of all 16k employees' PWs. Is he lying to us?

I work for a company which has ~16,000 employees. Periodically, our VP of IT sends out a newsletter with "tech-tips" and misc IT stuff. The topic of this week's newsletter was "password security". ...
65
votes
13answers
13k 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 ...
63
votes
7answers
8k views

Touch Screen Password Guessing by Fingerprint Trace

After eating some garlic bread at a friend's who is not security-aware, she managed to quickly determine the PIN code to unlock the screen of my Samsung SIII. She figured this out by simply holding ...
63
votes
5answers
21k 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. ...
59
votes
3answers
14k 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 ...
58
votes
10answers
17k views

Bad practice to have a “god” password?

Is it bad security practice to have a password that will allow you to access any user account on a website for support purposes? The password would be stored in a secure manner and would be super ...
57
votes
4answers
11k 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 ...
55
votes
21answers
10k views

How can I avoid my password being harvested by key loggers from internet cafes?

During traveling, especially in poor countries, sometimes you are going to need to use the internet at an internet cafe and you really can't be sure whether anyone has installed anything to listen to ...
54
votes
12answers
9k 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 ...
54
votes
7answers
33k 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 ...
53
votes
5answers
13k 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?
53
votes
12answers
3k views

How do you log in from an unsecured computer?

Suppose that you are on a cybercafe, at a friend's home or at your work office, and you need to log in on a site, but you feel that the the computer can not be trusted (e.g. your friend isn't ...
52
votes
3answers
18k views

How can I create a password that says “SALT ME!” when hashed?

How can I create a password, which when directly hashed (without any salt) with md5 will return a string containing the 8 characters "SALT ME!". The hope is that a naive developer browsing through his ...
50
votes
8answers
78k 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 ...
46
votes
8answers
3k views

I'm an IT consultant. Should I discourage a client from telling me his password?

I'm an IT consultant. One client has known me for a few years. He wants me to do some work on his kids' laptop again. I'll need to log into his kids' Windows user account. (I'm guessing that multiple ...
45
votes
7answers
3k 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 ...
44
votes
9answers
4k views

Generic error message for wrong password or username - is this really helpful?

It is really common (and I would say it is some kind of security basic) to not show on the login page if the username or the password was wrong when a user tries to log in. One should show a generic ...
44
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 ...
42
votes
5answers
4k views

Is it safe to tell your users what kind of hashing algorithm you use?

For example, on the user registration page, is it safe to tell people "Your password will be stored as a one-way hash using the (whatever) algorithm."
42
votes
9answers
5k views

Can users make use of a password manager when banks tell them never to write passwords down?

Consider a user who wants to use a password manager for their banking passwords. Advice from banks usually says they should never write down their password. The user would be concerned about going ...
42
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 ...
41
votes
3answers
7k views

Paypal sent an email addressing me with one of my old passwords as my name

I got this email from service@intl.paypal.com, with the title: Your account has been limited until we hear from you. I think this is a scam / spoof email because I don't see any notification in my ...
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 ...
40
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.
39
votes
9answers
3k views

Isn't OAuth, OpenID, Facebook Connect, and others crazy from a security standpoint?

I work with APIs all the time and I work with web developers who insist that OAuth, OpenID, etc are far superior than a home-brew method. Every site seems to be using these as well now for ease of use ...
38
votes
2answers
4k views

Is it good practice to ban an IP address if too many login attempts are made from it?

Since an IP address does not necessarily represent a specific device, but probably a whole network/company/etc. does it at all make sense to block an IP address if there is a significant amount of ...
36
votes
7answers
3k views

“Real” Salt and “Fake” Salt

During a Q&A period at DEFCON this year, one member of the audience mentioned that we're using "fake salt" when concatenating a random value and a password before hashing. He defined "real salt" ...
36
votes
3answers
38k 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 ...
35
votes
10answers
3k views

Why do password strength requirements exist?

Password strength is now everything, and they force you to come up with passwords with digits, special characters, upper-case letters and whatnot. Apart from being a usability nightmare (even I as a ...
35
votes
2answers
4k 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 ...
34
votes
15answers
5k views

Why do people think that this is bad way to hash passwords?

Well, please tell me, what's wrong with this code: $password = "hello"; $password = md5($password); for($i=1;$i<20;$i++){ $password = md5($password); } It's exactly the same as this one: ...
34
votes
1answer
2k views

What's the risk if I accidently type my password into a username field (Windows logon)?

I'm used to logging into my personal Mac which is a password-only field (like waking from sleep mode). Sometimes I have to use a Windows network on which I have an account, but of course I have to ...
33
votes
5answers
5k 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, ...