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

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13
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7answers
8k views

Forgotten password or reset link, which is more secure to email?

I originally posted this as a reply here in this thread but didn't get much feedback on it, and now I'm curious as to what others think is the best approach, or if there is any difference between the ...
22
votes
5answers
2k views

Is it possible to increase the cost of BCrypt or PBKDF2 when its already calculated and without the original password?

I just wanted to know if you can increase the cost (iterations) of those two algorithms off-line. I want to increase the cost every year of my users passwords. One solution is to recalculate them ...
17
votes
3answers
6k views

Password in file .php

My connection.php file stores the credentials to connect to the database. <?php $objConnect = mysql_connect("localhost","username","password"); mysql_select_db("selectDB", $objConnect); ...
14
votes
2answers
3k views

What are the most common password salting methods?

I learned that the Sun guys used the login name as salt for password hashing. Is this a common approach? What are the most common salt values?
12
votes
2answers
1k views

Is there any advantage of bcrypt over multiple iterations of SHA-x/MD5?

I know that a good password hashing algorithm should be slow. MD5, SHA256, etc. are fast. So I've been adding multiple iterations of SHA-256 hashing to my web apps (around 50000). Getting the hash of ...
7
votes
6answers
3k views

Is denying login after incorrect attempts ineffective?

Generally denying login attempts after X amounts of incorrect attempts for Y amount of tries is a very basic way to prevent bruteforce attempts or malicious login attempts. Yet, surely doing this is ...
9
votes
1answer
2k views

How will security need to be changed if P=NP?

If we suppose that it is found that P=NP, how will security measures need to be changed? I'd like to know the major security measures that are affected, and how they would need to be changed. We can ...
6
votes
7answers
3k views

How can I best manage root passwords for many servers?

Lets say I have two racks with about 40 nix servers in them. I don't want to set all of the root user passwords all the same do I? If not how do you manage and keep up with all of the passwords? Is ...
6
votes
3answers
449 views

How can Microsoft validate a shorter password on Microsoft accounts (MSDN)?

I recently ran across this when logging into MSDN. (I saw this screen after typing my initial credentials.) I have a 20+ digit password, however there's apparently a new requirement for Microsoft ...
18
votes
5answers
961 views

Is there any legal reason to save a cleartext password?

I called customer service of a well known company and discovered that the operator had the ability to view my website password in clear text on her screen. I asked her about this and she defended the ...
14
votes
5answers
982 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?
14
votes
2answers
3k views

Tamper-proof BIOS password & settings storage with Trusted Platform Module?

In the olden days, one could trivially bypass BIOS passwords on most PCs by removing the BIOS battery and clearing the CMOS. My question is: On modern PCs equipped with a Trusted Platform Module ...
8
votes
5answers
3k views

How can one secure a password/key in source code [duplicate]

If there is a need for source code to have a password in it, how should this be secured? This is purely an example, but say there is an app that is using an API, and you don't want to expose ...
8
votes
3answers
2k views

Encrypting user data using password and forgot my password

I am planning to do a web application which stores a lot of personal stuff (info, photos...). And to give users a sense of protection, I want to encrypt the data before storing it to the database. ...
7
votes
2answers
921 views

How should I make diceware passphrases more memorable?

I find that truly random diceware passphrase, more often than not, either contain a word that is easily misspelled or has an order that is illogical. I think there are three ways to make a diceware ...
6
votes
3answers
20k 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 ...
4
votes
2answers
439 views

Can the human brain generate cryptographically secure random numbers?

A security conscious friend of mine was attempting to generate entropy using random dice rolls to generate a random password, and I became curious about the security of random number generators and ...
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 ...
5
votes
4answers
633 views

Can't brute force password cracking somehow be throttled?

Online articles mention the importance of a strong password and suggest that hacking tools allows bad guys to attempt millions of passwords per second. I am wondering why OSes and websites and such ...
5
votes
1answer
2k views

Security of bcrypt/sha256 key used with AES to encrypt a file

I'm looking to encrypt files using secure hashing and encryption algorithms in Python. Having used bcrypt in the past, I decided to use it for my passphrase calculator, then pass the output through ...
4
votes
2answers
304 views

Password strength metrics

In the question Source code as password I suggested using a combination of entropy and as @Lawtonfogle put it 'meatspace difficulty'. As suggested in the xkcd comic correct staple horse battery is a ...
3
votes
2answers
3k views

Is it a good idea to store Email addresses as hash only?

I am currently building a web service at http://write-math.com similar to http://detexify.kirelabs.org/ that should help users to get LaTeX code from drawn formulae. It is part of my bachelors thesis ...
11
votes
9answers
2k views

Why do we authenticate by prompting a user to enter both username and password? Does prompting the password only suffice?

I don't know why do we authenticate by prompting the user to enter both username and password. In my mental model, prompting password only suffices. The reason is as follows: Assume there are x ...
8
votes
3answers
2k views

What are the security implications of using TOTP for single factor authentication?

(Note: I am not actually planning to do this. This question is strictly theoretical.) TOTP is commonly used as the second factor in Two Factor Authentication. It is an open standard with available ...
6
votes
3answers
639 views

An alternative to traditional passwords: is there some merit to this idea?

If you've got a website aimed at people that are not neccessarily technically proficient, letting new users choose their own password isn't very secure because of the simple fact that a lot of people ...
4
votes
2answers
260 views

Is there a site like plaintextoffenders.com that shames companies that force insecure passwords?

I recently came across http://plaintextoffenders.com/ and I liked the idea. I wondered if there was a similar site that shames websites that force insecure passwords? I personally have a list of a ...
4
votes
4answers
442 views

Is it secure to use similar password over different accounts?

I have a strong password which is a long, unfamiliar word phrase. I would like make other account use a password with similar level of complexity but I don't like to remember so many password over ...
3
votes
7answers
3k views

Is it possible to detect password length from hash? Does doubling your password add more security?

Assuming a service doesn't store a plain text password, am I right in saying that the answer to this question depends on the service? On a bad service, the hash length is related to the password ...
0
votes
4answers
822 views

Is it bad practice to use the same password on different sites?

Is it considered bad practice to use the same password on separate sites, if so why? Even if the passwords to a site are compromised the attacker still doesn't know the user names or sites the same ...
135
votes
9answers
27k 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 ...
77
votes
12answers
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 ...
180
votes
7answers
38k 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 ...
30
votes
6answers
8k views

Length of passwords that are rainbow table safe

With large computing power (like what you can get in the Amazon cloud for example) you can generate huge rainbow tables for passwords. There also seems to be some large rainbow tables reachable that ...
39
votes
3answers
4k views

Security Review - password_hash implementation for PHP

I'm currently working on a "helper function" for PHP's core to make password hashing more secure and easier for the majority of developers. Basically, the goal is to make it so easy, that it's harder ...
53
votes
2answers
60k 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 ...
49
votes
10answers
11k views

Why does the user pick the password?

Almost every web service I can imagine has the user pick the password. Why is this? Couldn't the system choose a better password? It doesn't have to be some complicated mess; see ...
43
votes
9answers
4k 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 ...
26
votes
4answers
10k views

Is using SHA-512 for storing passwords tolerable?

I know that the best options to use for storing passwords are bcrypt/PBKDF2/scrypt. However, suppose you have to audit a system and it uses SHA-512 with salt. Is that "fine"? Or it is a vulnerability ...
24
votes
10answers
5k views

Password Management within an Organisation

Within an organisation there are many passwords such as those for root accounts on servers, hosting accounts, router logins and other such things, that need to be kept track of. I know in some ...
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 ...
37
votes
11answers
31k views

Are password-protected ZIP files secure?

Following my answer. If I can list contents of password-protected ZIP file, check the file types of each stored file and even replace it with another one, without actually knowing the password, then ...
37
votes
8answers
4k views

Why improvising your own Hash function out of existing hash functions is so bad

I'm afraid I'll have tomatoes thrown at me for asking this old question, but here goes. After reading that cooking up your own password hash out of existing hashing functions is dangerous over and ...
40
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" ...
22
votes
2answers
16k views

Why are GPUs so good at cracking passwords?

What is it about GPUs that lets them crack passwords so quickly? It seems like the driving force behind adopting good key-derivation functions for passwords (bcrpyt, PBKDF2, scrypt) instead of ...
7
votes
5answers
27k views

Modern high quality password dictionary

Has anyone come across any good password dictionary lately? Some of the lists I found dated back to 90's! Some are simply too big that I doubt their quality. There appears to be some work by someone ...
28
votes
7answers
3k views

What is a good way to authenticate a user to a smart phone?

What would be a good way to authenticate a user to a smart phone? By good, I mean that it is both secure, and user-friendly. Passwords don't seem to be the best fit because a password needs to be ...
20
votes
2answers
1k views

Can client-side hashing reduce the denial-of-service risk with slow hashes?

When storing user's passwords that you need to verify against (but not use as plaintext) the current state of the art is: Hash the password Use a salt Use a slow hash function - bcrypt, scrypt, etc. ...
27
votes
4answers
3k views

Is it safe to store a password hash history for preventing user to keep same password repeatedly in some cases?

I am developing an application in PHP and it uses bcrypt encryption to store passwords. I want to keep the history of hashes whenever the user changes the password. By doing this I want to stop the ...
28
votes
3answers
4k views

MD5 collision attacks: are they relevant in password hashing?

DISCLAIMER: This is not an endorsement of MD5 as a password hashing function. I know about parallelization, GPUs, and dedicated password hashing functions like bcrypt and scrypt. With that out of ...
21
votes
6answers
9k views

Is AES encrypting a password with itself more secure than SHA1?

This isn't really a practical question, but more a question of curiosity. I heard a CS professor recommend stepping up from md5ing passwords not to SHA1, but to AES encrypting the password using ...