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

learn more… | top users | synonyms

15
votes
8answers
4k views

What chars should I not allow in passwords?

I am planning to develop a website that require that the users register a username and a password. When I let the user choose a password, what chars should I allow the users to have in the password? ...
15
votes
2answers
2k views

Password and Generated number - How does it work?

In my company, they don't allow accessing the company email or servers from outside the company network. To access the email from outside the network, you have to use: Username, password and a number ...
15
votes
7answers
3k views

Password management/synchronization?

Is there a good enough service I could run on my own home (Linux) server that I could use for storing/accessing/synchronizing passwords so they could be available for me from multiple computers/places?...
15
votes
6answers
5k views

Do salts have to be random, or just unique and unknown?

First of all, my motive is to avoid storing the salt in the database as plain text. As far as this question is concerned, the salt is not stored in the database. After discussion in comments and in ...
15
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 ...
15
votes
7answers
373 views

Is a “security measure” that doesn't provide a security benefit actually harmful?

If a security measure is implemented that doesn't provide any additional security benefit, can it be considered harmful? As an example, consider a login page where the user is asked to enter their ...
15
votes
3answers
965 views

What can I do if my bank thinks my date of birth is “known only to me”?

My bank has recently replaced passwords with occasionally asking me information that is "known only to me". Such information includes my date of birth, postcode, and my mother’s maiden name. ...
15
votes
6answers
45k views

Recommend Length for Wi-FI PSK?

I currently have a network set up with WPA2 and AES encryption, the password is 8 characters long but was randomly generated and contains no dictionary words. However I'm concerned about the ...
15
votes
3answers
2k views

What is a good enough salt for a SaltedHash?

Since I'm hashing all passwords with each their own salt, is there a benefit to the salt being really random, or would an incremental counter or a guid be good enough? Also, is there a benefit of ...
15
votes
2answers
1k views

How does varying character type increase strength of password?

When creating a new password, people often recommend you use both uppercase and lowercase characters, numbers, and symbols. How does adding any of these increase the strength of a password? There ...
15
votes
2answers
983 views

Distance between two passwords

It is known that people reuse their passwords across different sites. The reuse can be done in two ways: using exactly same password for two different sites, slight modifying the password of one ...
15
votes
1answer
946 views

Linux /etc/shadow password change security

I wonder what happens what happens when I am changing my password on a Linux system. Basically all passwords are stored in a file called /etc/shadow or /etc/master.passwd in BSD-like systems as I do ...
15
votes
2answers
2k views

Are there some good papers (or discussions) on using Markov chains or Hidden Markov Models for password auditing/cracking?

As a programmer and language enthusiast I've been very interested in Markov chains for some time. Considering the influence of natural language on password and passphrase selection (by humans of ...
15
votes
3answers
5k views

Is it truly possible to store passwords securely, but be able to see the password?

Every place I looked, people recommended that storing passwords via encryption is like storing passwords in plain text. But every place I've looked, everyone recommends using a password manager like ...
15
votes
1answer
939 views

XKCD #936: under what assumptions is 1000 guesses/second over a network plausible?

In XKCD #936, a rate of 1000 password guesses/second is proposed as a "plausible attack on a weak remote web service". Under what assumptions is this rate plausible? It seems much too high to me. I ...
15
votes
2answers
10k views

Bypassing the BIOS password

Are there any reliable methods that allow an attacker to bypass a BIOS password, or alter BIOS settings without entering the password? A few ideas come to mind: The old battery trick (remove ...
15
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 (TPM)...
14
votes
2answers
1k views

Salting password with the first 8 bit of the password itself

Do you guys think salting password with the first 8 bit of the password itself will have same result as using stored salt to hash password? [Clarification] I am not storing salt but creating from the ...
14
votes
6answers
2k views

Is this login security enough?

I'm coming up with my next login system for admins of an e-commerce website, which will have this: login form is SSL secured password is converted to SHA-256 before being transmitted (bcrypt is too ...
14
votes
6answers
8k 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 ...
14
votes
2answers
1k views

Does it make sense to choose a longer password than the output of a hash?

Let's take MD5 for example: It outputs a 128-bit hash. Does it make sense (in theory) to choose an input (password) which is itself longer than 128-bit? Does it increase the probability of a ...
14
votes
4answers
989 views

If a website allows another person to get a list of the site's users passwords, how likely is it that the passwords are stored in cleartext?

We had an incident where some of our managers were given passwords for the people they supervise using a particular company website. Ostensibly it was done so the managers could check in on the users ...
14
votes
4answers
2k views

Looking for example of well-known app using unsalted hashes

Does anyone know of a well-known application that still uses unsalted hashes for password storage? I'm looking for an example for an upcoming lecture on Rainbow Tables, and I think it would add ...
14
votes
5answers
2k views

Can sites which check your password as you type pose a security risk?

Some sites that I use check my password as I type it into the login (not registration) form. So, for example, to begin with I might have: Username: sapi ✓ Password: passw × and by the time I've ...
14
votes
3answers
2k views

Should I reject obviously poor passwords?

UPDATE: My questions and concerns below boil down to: "Should I reject obviously poor passwords like 'hellomydarling' or 'password'? My guess is yes and I want to know to what extent. I'm using a ...
14
votes
8answers
8k views

Are services like “LastPass” less secure, as they have all my passwords protected by a single password?

If the LastPass service has all my passwords and someone gets access to my LastPass password, this person will have access to all my passwords. Isn't that bad for security?
14
votes
1answer
10k views

Why use an authentication token instead of the username/password per request?

The author of http://stackoverflow.com/a/477578/14731 recommends: DO NOT STORE THE PERSISTENT LOGIN COOKIE (TOKEN) IN YOUR DATABASE, ONLY A HASH OF IT! [...] use strong salted hashing (bcrypt / ...
14
votes
6answers
929 views

Is there additional security value in using passwords with words or phrases in non-English languages?

I was thinking about correct horse battery staple. I am not a native English speaker. In my language, the above could be written as: vqrno kon bateriq telbod OR вярно кон батерия телбод. Keep in ...
14
votes
6answers
687 views

Primary Key as Salt?

Is it okay to use the primary key as the salt in a Users table? The only disadvantage that I can see is if the PK changes (unlikely), then the passwords break. What are your thoughts?
14
votes
2answers
14k views

How can I find if my password has been posted online?

I have just received this email from AbeBooks.com: Hello AbeBooks Customer, This is an important message from AbeBooks.com. As part of our routine security monitoring, we have learned ...
14
votes
2answers
3k views

How many passwords does the average user know?

Looking for research on the count and complexity of passwords that an average user is actively using. Note: Also, just to be clear, by research, this is not a request for you to respond with an ...
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?
14
votes
5answers
8k views

Is it okay for API secret to be stored in plain text or decrypt-able?

Aren't API keys considered usernames and API secrets considered passwords? Why is it that API servers like Amazon Web Services allow you to view your API secret in plain text? It makes me think they ...
14
votes
3answers
9k views

Cracking MS-CACHE v2 hashes using GPU

As most people here will know, Windows caches domain/AD credentials in a format known as MS-Cache v2. Obviously, these would be excellent passwords to gain during a penetration test when local access ...
14
votes
6answers
1k views

Is there any security risk in storing hashed variations of passwords?

For example, if hypothetically an application requirement was to tell users when their password might have failed because caps-lock was turned on, and hypothetically there was no way for the ...
14
votes
2answers
8k views

With PBKDF2, what is an optimal Hash size in bytes? What about the size of the salt?

When creating a hash with PBKDF2, it allows the developer to choose the size of the hash. Is longer always better? Also, what about the size of the random salt? Should that be the same size as the ...
14
votes
7answers
1k views

Aren't password managers still incredibly risky?

I understand the utility in having one application remember a bunch of long, randomized passwords, but all you'd need is one well-placed phishing scam or a keylogger and they get all the keys to the ...
14
votes
2answers
234 views

Would suggesting a random passphrase during sign-up hurt overall security?

I've been looking for ways to improve security and security awareness for both internal and external clients and I happened upon the idea of generating a one-time, random "password suggestion" on the ...
14
votes
3answers
4k views

Should security question answers be case-sensitive?

Question In the case of security questions being used to reset an account password, what is considered best practice for handling case-sensitivity on the security question answers? Scenario An ...
14
votes
3answers
23k views

Is a password protected PDF file safe for bank statement attachments?

My bank emails my monthly statement to me in a password protected PDF attachment. Is this a secure method of transmitting something as sensitive as bank statement?
14
votes
2answers
1k views

Can a Firefox add-on or plug-in access the user's websites' saved passwords in decrypted mode?

Going deeper into the previous question on Firefox plugins and add-ons malware risks: Could a Firefox add-on potentially decode and capture the encrypted websites' passwords saved in the browser?
14
votes
2answers
545 views

Concrete figures on password cracking in the wild

While password guessing is a science, not every attacker out there is up-to-date with the latest advances or cares to invest in GPUs or FPGAs. It's easy enough to test online password guessing ...
13
votes
1answer
3k views

Should I hash my passwords even if I am only allowed to generate limited traffic?

At this moment I'm busy working on an webapp with a friend of mine. The main problem we have is that we are only allowed to generate 50 GB a month in datatraffic. My question is: Does hashing the ...
13
votes
5answers
2k views

Why should I have secure passwords for sites that I pay bills on?

What's the worst that can happen, the hackers will pay my bills for me? Assume that this isn't a malicious hacker out to disconnect my electricity. What kind of concerns are there for my finances, ...
13
votes
2answers
2k views

Linux password changed. Is this an attack or a hardware glitch?

My Linux (Ubuntu 12.04) password suddenly changed last night and I'm not sure if this is an attack or just a hardware/user error. This is on a personal/non-server box. Several strange events led up to ...
13
votes
6answers
2k views

Does prepending a salt to the password instead of inserting it in the middle decrease security?

I read somewhere that adding a salt at the beginning of a password before hashing it is a bad idea. Instead, the article claimed it is much more secure to insert it somewhere in the middle of the ...
13
votes
3answers
2k views

Known characters in passwords?

I generate passwords for everything that requires security using the following method: ksoviero@ksoviero-Latitude-E7440:~$ head -c 16 /dev/urandom | base64 gorv/cp+lSiwiEfKck2dVg== 256^16 ...
13
votes
8answers
3k views

Facebook account keeps getting hacked, can't seem to figure out why or how?

One of my friends, she has a lot of friends on Facebook, and uses it for marketing. Her account keeps getting broken into. Her password gets reset and/or gets locked for changing resetting password ...
13
votes
3answers
14k views

Can password-protected zip files be broken without brute force?

You have a zip file that you created with 7z to password-protect it with AES 128. Can a smart adversary extract the data only through brute force, or is the file vulnerable to other attacks - such as, ...
13
votes
4answers
2k views

Is it “standard” to SMS passwords?

When I get credentials for a new machine, my company will often send the login id in email, then SMS (or sometimes Skype msg) the password. This is obviously in order to separate the login and ...