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

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95
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?
3
votes
1answer
87 views

Unable to completely enforce password policy

PCI DSS has a few requirements regarding the password policy (like remember last four passwords, change password every 90 days, use at least seven numeric and alphabetic characters and more). These ...
157
votes
10answers
34k 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 ...
0
votes
1answer
73 views

Is there a way to securely check if a password is one of the most used ones?

So lets's say that a user wants to register to some website. For whatever reason, I want to not allow that password if it is one of the top 100 passwords used on my site (So I'm not checking against ...
9
votes
3answers
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 ...
8
votes
5answers
3k views

Is forcing users to change passwords useful?

In many places, there's a policy that force the user changing it's password once a few months. The logic here is, that even if the password have leaked somehow, it'll be abused only for a relatively ...
290
votes
8answers
52k 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 ...
2
votes
2answers
49 views

Would a multilingual Diceware password be more secure than a monolingual one? [duplicate]

I've been reading up on Diceware recently, and I'm wondering if using a mix of languages would make it even more secure. On the face of it, it would force a potential attacker to consider an even ...
5
votes
3answers
316 views

1Password for team how secure it is?

I would like to ask you opinion about how secure is the 1Passowrd for Teams. For someone who doesn't know how 1Password - Personal use - works here a summary: You create a master password (hard to ...
8
votes
3answers
38k views

Four-way Handshake in WPA-Personal (WPA-PSK)

Can someone explain to me in what consists the Four-way Handshake in WPA-Personal (WPA with Pre-Shared Key), which informations are being sent between AP and client, how is it possible to find the AP ...
0
votes
2answers
96 views

Password based Asymmetric Key generation

I am looking for a password based key derivation scheme that results in an asymmetric key pair. I have worked with PBKDF and its variants but could not come up with any way of generating a key pair. I ...
3
votes
2answers
236 views

Am I encrypting and storing an array of user-details correctly?

I came up with a user-details-storing procedure that was, in the beginning, based on actual security-literature – but then I just kept writing without really doing all the cross-checking I should have ...
6
votes
1answer
592 views

Gmail lets me use my old password

My university's email works through Gmail and I can log on to it either through my uni's website or in Gmail. I recently changed my password and I use it to log in to the schools secure WiFi, school ...
2
votes
1answer
108 views

How might a PIN based Web authentication scheme work?

I'm interested in implementing PIN based authentication for a web application, similar to what Facebook provides in their mobile web site. Here is the user flow: User visits the site for the first ...
3
votes
3answers
624 views

What are the benefits to a two-page login system for a webapp?

I have noticed many website going to a two-page (not two-factor) login system - where you enter your username on page 1 and click submit, and then enter your password on page two and click submit. ...
1
vote
2answers
64 views

Custom word list generation for a specific web domain

I am looking for a tool that generates a set of word lists based on the words it finds on the pages of a particular web domain. This question has an answer that generates permuted word lists starting ...
0
votes
0answers
32 views

What is a straightforward way to brute force CLI applications?

This is a question to maybe more CTF-experienced guys among you. I wonder how you generally brute force a simple CLI application. For example if you have an application which tells you a user's data ...
39
votes
7answers
31k 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 ...
11
votes
5answers
2k views

Passwords - any statistics on user behavior?

I'm looking for analyses of how users choose and use passwords. I'm sure there are many resources out there that analyze user passwords. For instance, I've seen many people analyze dumps of password ...
1
vote
3answers
167 views

Are longer passwords safer even if the encryption/database security used is compromised?

Let me preface this that I am having a lot of trouble wording my question. Hopefully my description will help clarify. I have always wondered if long passwords actually provide you any more security ...
166
votes
8answers
34k views

Why are salted hashes more secure for password storage?

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 ...
6
votes
1answer
154 views

Samba printer usernames and passwords , security problem

Password leaks , printing from Linux client to windows based print server When authenticating Linux users for using a windows share printer on their machine, the windows domain user-name and password ...
2
votes
2answers
476 views

Practical steps for encrypting an encryption key for data stored in MySQL

So I'm working on my first project where user data is stored as encrypted using the user's password as (part of) the key. I have read many similar things about best practices, but the details seems to ...
1
vote
0answers
85 views

Is Trillian application unsafe? (Got “Someone has your password” message from Google)

Trying to connect to GoogleTalk from the Trillian app for Android (a universal instant messenger app), I got denied even with the correct password. Then Google e-mailed me saying that my password is ...
1
vote
2answers
141 views

Password may not be similiar to last 5 passwords [duplicate]

SAP NetWeaver has a password policy to prevent your new password beeing similiar to the last 5 passwords. Are the passwords stored in plaintext to verify this? Or is something like a soundex value ...
3
votes
6answers
211 views

How secure is this process for creating passwords?

I've been research into how to be as secure as possible when it comes to password security for online services and websites. Obviously there are some big no no's like using dictionary words, using the ...
0
votes
1answer
83 views

Is Entropy all that matters in a Password? [duplicate]

My question is, is it more reliable having a password that is composed by words like FootballPractice more secure than using a password that has only 2 or 3 bits less, for example FootbalPractic , my ...
16
votes
5answers
5k views

Is an 80 bit password good enough for all practical purposes?

I know that asking how many bits of entropy comprise a strong password is rather like asking the length of a piece of string. But assuming the NSA is not on to you, and that it is hardly worthwhile ...
14
votes
3answers
5k views

Calculating password entropy?

Whenever I look at password entropy, the only equation I ever see is E = log2(RL) = log2(R) * L, where E is password entropy, R is the range of available characters, and L is the password length. I ...
2
votes
1answer
57 views

Remembering email in login form

After logging out Google remembers recently used email addresses in the login form so the user only needs to enter the password. See accounts.google.com. How secure is it? What factors should I ...
1
vote
1answer
63 views

Distinct error messages for wrong email / password

I want to continue discussion started in this question "Username and/or Password Invalid" - Why do websites show this kind of message instead of informing the user which one was wrong? but ...
2
votes
3answers
141 views

Parameters for PBKDF2 for password hashing

I use PBKDF2 with SHA-256 to store hashes of passwords. I use the following parameters: number of iterations desired = 1024 length of the salt in bytes = 16 length of the derived key ...
4
votes
4answers
316 views

If A Password Is Unique, Does It Really Matter How “Strong” It Is?

People seemed to find this "If a Password is Super-Strong Does it Matter if It's Unique" question very interesting, but it actually reminded me that the converse question is interesting, too: If you ...
0
votes
1answer
26 views

Creating secure random output that is repeatable across machines [duplicate]

I'm having trouble figuring out a solution to this problem. Basically what i am trying to do is create random data that can be repeated across multiple machines by a user but is also secure from ...
12
votes
2answers
4k views

Estimating the size of a rainbow table

What are rainbow tables and how are they used? Gives a very precise answer about what rainbow tables are and how they are used. I had always confused hash-tables and rainbow tables. My question is ...
8
votes
7answers
346 views

Strong password vs. restriction on number of attempts

To begin with, I am considering the password protection of standard internet services like Gmail or Dropbox. They often force users to choose a "strong" password, that is many characters, including ...
1
vote
2answers
115 views

Exclude passwords with repeating letters

It would cut down a lot of time of the brute force attack if some of those passwords like "aaaaaa" wouldn't appear. How can this be achieved in Hydra or some other brute force software?
2
votes
4answers
125 views

Justifying strong 1st factor in the context of multi factor authentication — beyond passwords

I am wondering if you need strong 1st factor (for theoretical correctness, please note it is the knowledge factor -- not necessarily a password, but definitely also includes strong passwords)? What ...
-2
votes
3answers
317 views

Why is encryption bad for passwords?

We use PGP for almost everything and it's so infeasible to bruteforce that it's considered secure. This is the guiding principle beyond CryptoLocker. But for stuff like e-mail, SSH and HTTPS, it's ...
2
votes
2answers
68 views

Securely generate a rng seed using a small number

I'm trying to figure out a secure method to generate a rng seed to a rng using a small pin number that is 5 digits. The issue that i can see with this is an attacker could very easily just loop ...
1
vote
1answer
80 views

How much more difficult does it become to crack a password when appending a 5-digit pin?

I have a quick question regarding password cracking. Lets say you append a 5 digit pin on the end of your password. An example would be instead of a password of "password" it would be ...
1
vote
1answer
69 views

Why is the password field blanked in the registration form if the validation fail? [duplicate]

Is it really a problem if you send back the password when the validation fail on a registration form? I understand that the html that is sent back could be cached on the computer of the person ...
36
votes
15answers
6k 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: ...
-1
votes
1answer
45 views

What are the exclusions for using a very long and random password? [closed]

It is a good practise to always use long (63 character) and random passwords. Question: But what are the exclusions? Can someone mention cases? Example: when console login is needed (so not via ...
1
vote
2answers
74 views

Using emoticons in passwords

I'm coming up with a password to use for my banking website, XKCD style. Furthermore, I'm considering adding in an emoticon (say, a <3) How many bits of entropy does an emoticon add to my ...
1
vote
0answers
109 views

Can password hashing both client side and on the back end improve security if we don't necessarily trust the server? [duplicate]

I want to know if it ever makes sense to hash a password client side and rehash it again on the back end. I've not seen this done before which makes me suspicious as to whether it really does add ...
3
votes
5answers
217 views

How should I store a physical written copy of my password? [duplicate]

I can employ all the fancy encryption and the randomest of passwords to my hard drive, but it won't do me any good if I don't remember how to log in. It seems sensible to write down my password, ...
0
votes
1answer
128 views

Brute force a hard drive when most of the password is known

I need to access a hard drive that is encrypted with LUKS. The password provided is incorrect, however it is only incorrect by a character or so. The password itself is very strong and above 30 ...
1
vote
0answers
56 views

Is that a way break Linux user password by bypassing grub protected?

The best way to delve into others Linux machine is by editing the grub. Many will start by, editing the line ro quite splash as rw init=/bin/bash during the startup (usually by pressing button e on ...
1
vote
2answers
100 views

Is it a good idea to combine words from different languages to increase a password's strength? [duplicate]

I was thinking of a way to generate a password that is easy to remember, but hard to crack, like the famous "correct horse battery staple" suggested by XKCD, also discussed here, and I've realized ...