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

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46
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9answers
5k 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 ...
23
votes
5answers
2k views

When hashing passwords, is it ok to use the hashed password as the salt?

I don't like this idea. But I can not come up with a technical argument against it. Can somebody explain it to me? The basic idea is: $passwd = 'foo'; $salt = hash($passwd); $finalHash = hash($passwd ...
12
votes
4answers
2k views

Why use random salts?

I read this blogpost on how to store passwords in a database, the secure way. Elbert tells us to do this: Generate a random salt and include something random and the username in it. Hash this. Hash ...
453
votes
14answers
76k 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 ...
19
votes
3answers
4k views

Is a password in the clipboard vulnerable to attacks?

I see situations where you may have to input the same password more than once. You may type it in a text editor and copy it to clipboard, to paste it two or more times. In what scenarios this could ...
13
votes
3answers
13k 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, ...
3
votes
2answers
7k views

How long it will take to crack a RAR password?

I wonder how long it will take to crack 16 character alphanumeric WinRAR password for a mini supercomputer. As far as I know graphic cards are preferred over CPUs to crack passwords nowadays. If we ...
1
vote
1answer
76 views

Parameters in output of password hashing function

A number of encryption functions include their tuning parameters in the output. For example, SCrypt, which I've been considering for an app I'm building, outputs in the following format: ...
4
votes
2answers
870 views

user authentication by decrypting a random blob

Normal user authentication is done by comparing "hash"-values. A simple example of this: The user password is hashed with PBKDF2 on the client using a salt (the salt is the hash of the user password ...
7
votes
4answers
1k views

Why does getting a password wrong takes more time than not

I type my password to login to Win or Linux. Case 1: I get it right. Almost instant reaction. Case 2: I misspelled it. It takes a while, and then rebounds. Why does it takes longer to identify a ...
12
votes
2answers
769 views

Zip file with two password

I used this command to password protect a zip file on Linux : zip -P 9000 hash.zip hash.py and it creates the zip file just fine, then I wrote a program to test every possible password on it from 1 ...
7
votes
8answers
1k views

How easy is it to find a password in a huge text file?

Say that my password is PASSWORD1 I have a 10MB jumbled text file. I hide my password in two parts in the text, between > and < so I can find it myself. Then I put the 2 parts together and add the ...
2
votes
1answer
605 views

UUID and Open_id in cookie 'good' enough?

I am using Tomcat 7, jsp to build a small website. I am new to security and it is a school project so using Spring Security is not an option. I am attempting to store UUID and Open_id in the clients ...
6
votes
1answer
1k views

Reducing password length with hash function

Suppose I would like to use a very long string as a password. As an example we can just say this string is 100 characters in length. However, suppose the application for which I would like to use ...
2
votes
2answers
427 views

Is there any way of recover a locked drive using TPM?

Just reading I learned about the TPM technology and how it works. However, it make me wonder... if the motherboard crashes, is the data lost forever? Because you can't use the drive in other system ...
26
votes
2answers
20k 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 ...
0
votes
2answers
436 views

Recover password or password hash from locked account

I have a locked administrator account. Other accounts are unlocked, but they have no rights. I want to get a password from the locked account, or maybe password hash, if possible.
3
votes
1answer
490 views

Can a user's Apple Keychain be opened on a different computer?

Apple uses a nice keychain. This is used by, for example, Google's Chrome browser. Imagine a user copies all the keychain files. Would that user be able to unlock the keychain, if they knew the ...
7
votes
2answers
2k views

When taking ownership of a TPM in Windows 7, how is the SRK derived from the password?

When you take ownership of a TPM in Windows 7 you encounter a screen like this: Based on this document, it is my understanding that completing this dialog box somehow results in the generation of ...
-3
votes
2answers
2k views

Is pixel based image encryption secure?

I have encrypted an image using pixel encryption method. I just used a bmp image for that. What I did is, I retrieved each pixel value from the image and obtained the value of red, green and blue ...
14
votes
2answers
542 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 ...
84
votes
8answers
17k 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 ...
3
votes
2answers
194 views

What exactly is the impact on security when forcing user passwords to contain a particular character?

Some years ago a sysadmin of large computing centre (on a campus) enforced the password of every single user to contain the character $ at an arbitrary position. They soon dropped this policy but I ...
5
votes
4answers
2k views

Temporary passwords e-mailed out as plain text

Is this a security issue? Many big ecommerce platform companies use this feature. Where if you forgot your password, they e-mail you a temp password. Could someone potentially figure out the ...
3
votes
1answer
922 views

Pointers for john the ripper rulesets

I've been pouring over the JtR ruleset documentation and making little progress. I understand how to use it to make various permutations from a given wordlist, that's fine. However, I'm trying to ...
11
votes
3answers
1k views

How much information about the reason for an unsuccessful login should a web application give?

After an unsuccessful login attempt, should I inform the user about its reason? Or more generally, how much information about the reason for an unsuccessful login attempt should a web application ...
8
votes
3answers
579 views

Increase the security of an already stored password hash

Right now we're using 1024 byte PBKDF2 with 256 byte user-specific salt and variable iterations. However, I would much prefer to be able to, perhaps once every year or two, to be able to flat out ...
2
votes
2answers
618 views

MySQL Access Control?

I have read somewhere that it is better to have two different MySQL logins in order to prevent hacking. What I mean is having one MySQL login for read access (SELECT permission) and another login for ...
18
votes
7answers
2k views

Are password complexity rules counterproductive?

In creating a login for this site I chose a nondictionary password that would be extremely hard to guess, but easy to remember. I was told that it did not meet complexity rules. After several ...
1
vote
2answers
1k views

Password Protected Zip: if attacker had one file, can use it to decrypt all files?

Consider a folder containing the following files: (file1.txt, file2.doc, file3.pdf) all zipped and password protected, if attacker had one of these file, can use it for decrypting all without knowing ...
202
votes
17answers
17k 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 ...
6
votes
4answers
2k views

Is GPG suitable as part of a password manager and generator?

I assume that GPG is very strong to crack, guess, etc. Since I have confidence in GPG, would it be appropriate to use my GPG key as the master key for a password manager or generator?
5
votes
3answers
974 views

Tools helps: First time cracking passwords

I am trying to crack passwords on two Windows member servers (2003 and 2008). There is no Active Directory. Each user seems to use the same password across servers, workstations, etc. I have access to ...
3
votes
3answers
545 views

Client-Side Hashing to decrease value of password guessing heuristics

Yes, this is 'yet another client-side hashing' question. But, don't leave yet, I think there is some value here. I'd like to do something to mitigate the affect on the community as a whole when my ...
12
votes
3answers
588 views

Is it inconsistent to tell users to “not click on password links in email”, and requiring clicks on “forgot password” links?

On one hand, IT Security shops have been telling users to not click on links in email because they can do damage to your computer, or phish your personal information. Many of those issues are ...
3
votes
7answers
571 views

How to provide security for passwords stored in Database? [duplicate]

Passwords of end Users are stored in Database which is encrypted (using one way hash like MD5). Apart from me, there are 'other' people belonging to other teams who have access to Database which means ...
1
vote
3answers
572 views

What about fuzzy passwords? For “correct” entry within a margin of error?

I'm wondering if a fuzzy password system would be in any way beneficial to users, or worth implementing. The idea would be that a certain margin of error is acceptable for allowing the user to log ...
3
votes
4answers
4k views

Yahoo Email Keeps Getting Phished

I keep getting spam emails from myself (and I am sending them to others as well) on my Yahoo Mail account. I have already went through two password changes which I thought were secure. My very last ...
3
votes
2answers
2k views

LastPass One Time Recovery Passwords--How?

The LastPass password manager stores One Time Recovery Passwords locally in each browser you use the plugin with: http://helpdesk.lastpass.com/account-recovery/ My question is, how can you have more ...
1
vote
2answers
742 views

What is the safest way to store a password in a single file?

I've been reading about it. This article helped me a lot. But the more I read the more complicated it seems. For example: Is it better to use bcrypt, or PBKDF2, sha2 or something else for the salt? ...
5
votes
1answer
436 views

Need to ephemerally store third-party password

One particular web service that I am writing interfaces with an API. Each API call requires the user's username and password to be sent, no state is maintained. Ideally, when using my web service the ...
6
votes
2answers
3k views

When, exactly, should old password reset tokens be deleted?

I'm trying to figure out best practices for working with password reset tokens. Say a user initiates the password reset process and the are emailed the reset token and we store a hashed copy in the ...
5
votes
2answers
4k views

File security when encrypting files directly with the openssl command / and what about SHA1 hashing password first?

I've been using this command to encrypt files for a while now: openssl aes-256-cbc -a -salt -in secrets.txt -out secrets.txt.enc Then I type in a password. Can someone tell me, roughly speaking, ...
1
vote
3answers
124 views

How to protect against an attack where a person claims to be in a position of authority?

In an office if a person approaches an employee and claims to be a new IT staff and to give them access to their computer, what can prevent this kind of attack? I've worked a couple tech support jobs ...
5
votes
5answers
6k views

Password reset links: random value or authenticated message?

Which is better? Create tamper-proof encrypted password reset token which contains the user id and the expiration time within the encrypted token. Generate a random token and store it in the ...
8
votes
2answers
772 views

How to proceed if a new hash algorithm for passwords is introduced?

I have an e-mail address at a certain institution. A few days ago they sent me an e-mail (in German), which I'd like to paraphrase without revealing the institution: Dear Madams and Sirs, a ...
0
votes
1answer
224 views

What type of attack should be used in order to pass this authentication

I am practicing the Astalavista Wargames and i came across this challenge. The question is: Bob wrote a piece of software but the password verification doesn't seem to work. You must find a way to log ...
2
votes
3answers
145 views

Is password authentication worse that signed messaging if done over SSL?

Let there is a public API: HTTP-based via SSL there are no browsers, just connections between custom written programs The first authentication scheme that came to my mind was... client signs their ...
5
votes
1answer
488 views

How genuine are password entropy calculations?

I apologise for perhaps the confusing title, I'll try and elaborate a little better. Many discussions I see surrounding password entropy focus on the specific context of the range of choices ...
5
votes
2answers
313 views

Passphrase using same word several times

I used a trivial 3-letter dictionary word five times in a row (smth similar to pwdpwdpwdpwdpwd), and am surprised to find my self in the list of hacked accounts in a penetration test using a ...