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

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761
votes
23answers
153k 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 ...
455
votes
11answers
93k 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 ...
423
votes
14answers
73k 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 where I actually care ...
398
votes
21answers
80k 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 ...
374
votes
5answers
122k 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 ...
332
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 ...
321
votes
11answers
40k 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. ...
268
votes
8answers
47k 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 ...
193
votes
17answers
16k 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 ...
184
votes
7answers
39k 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 ...
158
votes
8answers
31k 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 ...
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 ...
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 ...
142
votes
5answers
20k 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 ...
130
votes
16answers
17k views

Is the BBC’s advice on choosing a password sensible?

In this article on the BBC’s website they offer advice on how to develop a password. The steps are as follows. Step 1: Choose an artist (a recording artist I presume) Lets choose as an example ...
108
votes
6answers
42k 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. ...
102
votes
4answers
25k 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 ...
96
votes
17answers
23k views

Is “password knocking” a good idea?

With port knocking, you have to "knock" on specific ports in defined order to expose a port on which service is running. How about password knocking? For example you have three passwords: A, B and C. ...
96
votes
14answers
18k views

Why did customer services say using symbols in a password is insecure?

I am using an online service that I recently had to reset my password because I forgot it. When I went to change password I wanted to use one with a symbol !@£$%^&*(). When I clicked "confirm ...
94
votes
12answers
13k views

Explain Security to Employer

My employer wants/wanted to install a 3rd party app on my personal cell phone. One of the issues that we are still not seeing eye-to-eye with is regarding security. Here are some issues that concern ...
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 ...
91
votes
11answers
13k views

Technology that can survive a “Rubber-Hose attack”

In the documentary film Citizenfour, Edward Snowden says about documents: I'm comfortable in my technical ability to protect [documents]. I mean you could literally shoot me or torture me and ...
91
votes
11answers
13k views

How critical is it to keep your password length secret?

Is keeping your password length secret critical to security? Does someone knowing that you have a password length of say 17 make the password drastically easier to brute force?
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 ...
84
votes
17answers
13k views

How to tell users that they shouldn't disclose their password over the phone to our help desk?

I work for a help desk, and we recently launched an online service where our members can log in. A problem we are having is that users who are calling us often ask us to confirm that the password ...
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 ...
82
votes
8answers
12k views

If a provider sees the last 4 characters of my password, can they see it in full?

I have some domains/websites as well as emails with Bluehost. Every time I need support, they need the last 4 characters of my main password for the account. They cannot tell me how they store the ...
81
votes
11answers
15k 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 ...
81
votes
8answers
15k 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 ...
79
votes
10answers
12k views

New Gmail login system—going against conventional wisdom?

I noticed that the new gmail login asks for username first, and then confirms if such username exists, before asking for password input. Does this not go against conventional security wisdom to not ...
77
votes
8answers
8k views

Why should you redirect the user to a login page after a password reset?

The OWASP Forgot Password Cheat Sheet suggests: Whenever a successful password reset occurs, the session should be invalidated and the user redirected to the login page I'm failing to understand ...
76
votes
13answers
24k views

Why do sites implement locking after three 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 three ...
75
votes
9answers
70k views

How safe are password managers like LastPass?

I use LastPass to store and use my passwords, so I do not have duplicate passwords even if I have to register four to five different accounts a day, and the passwords are long. How safe are password ...
72
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 ...
72
votes
14answers
7k views

How to store passwords written on a physical notebook?

Answers to the question "How safe are password managers like LastPass?" suggest that storing personal passwords on a physical notebook might be a reasonable option: I know someone who won't use ...
71
votes
10answers
12k views

If I enter a password on the wrong site, should I consider it compromised?

I have recently started to make use of a password manager and good password practices. I have a different password for each site that I use. If I accidentally use the password from another site when ...
71
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". ...
69
votes
11answers
13k views

Will typing my password twice make it more secure? Or typing each character twice?

If I type my password twice (like: PwdThingPwdThing), OR type every character twice (like: PPwwddTThhiinngg) will that make it substantially more secure than it already is? Assume that it is already ...
69
votes
5answers
28k 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?
68
votes
7answers
17k 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 ...
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 ...
63
votes
3answers
21k 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 ...
63
votes
11answers
9k views

Is there any way my password is hashed, if I'm only ever asked to provide 5 out of many characters? [duplicate]

There is a system that, on a login form, presents about 40 boxes for password letters (to hide password's actual length), and only random ones (the same amount each time) are editable. Explanation is ...
63
votes
8answers
7k views

Is forcing users to use a strong password effective?

I am designing a service that would, among other things, store sensitive information. To ensure no unauthorized access of this information, it would be encrypted with a key derived from their password ...
62
votes
21answers
16k 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 ...
61
votes
10answers
18k 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 ...
61
votes
12answers
9k views

Do we really need a long and complicated password for websites?

Most of websites that handle important information (Gmail, for instance) have some kind of brute force protection. Sometimes if you try more than X times it will lock the account or at least give you ...
61
votes
12answers
12k 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 ...
61
votes
12answers
12k 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 ...
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 ...