Tagged Questions
2
votes
2answers
42 views
Does glibc2 version of the crypt function still use DES for alternative hashing methods?
I'm trying to understand how typical Linux distributions generate the password field for entries in /etc/shadow. I can't figure out what encryption algorithm is being used to produce the encrypted ...
21
votes
2answers
1k views
Does versioning an encrypted file make it less secure?
Suppose I use KeePassX as a password manager, and I store the kdb file in Sparkleshare folder as a way for backing up and syncing with multiple devices.
The kdb file in itself would be encrypted, but ...
3
votes
1answer
152 views
How to determine hashes/second in password cryptanalysis
I'm working on my dissertation concerning cryptanalysis on password hashes. As part of my research, I aim to crack a number of passwords with John the Ripper and rainbowcrack-mt.
I'd like to ...
1
vote
1answer
41 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:
...
10
votes
2answers
2k 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 ...
5
votes
3answers
242 views
Use of rainbow tables with the NY Times hack?
The NY Times recently published a story about how they were hacked during a four month period. The hacks allegedly were carried out by part of the Chinese military.
One part of the story that ...
0
votes
1answer
149 views
Storing Private Keys Generated on Server with specific User's Password Securely
I am currently building a system (PHP Web Application Framework) that creates an RSA Key Pair for a user to allow other users to send secure information from one to another. The public key is ...
-3
votes
1answer
132 views
What is the highest limit of security in the biggest agencies of the world? [closed]
A general question clicks in my mind, that there are many ways to bypass the security.
So, what is the highest degree of security?
61
votes
13answers
5k 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". ...
2
votes
1answer
502 views
Clarification on how rainbow tables work
If you goto : http://www.hanewin.net/encrypt/aes/aes-test.htm
for "Key in Hex" enter
00000000000000000000000000000056
for "Plaintext in Hex" enter
00000000000000000000000000000000
and click on ...
18
votes
5answers
1k views
How valuable is secrecy of an algorithm?
On the surface, the inadvisability of security through obscurity is directly at odds with the concept of shared secrets (i.e. "passwords"). Which is to say: if secrecy around passwords is valuable, ...
-4
votes
2answers
224 views
How do I construct a rainbow table to crack a 6 character password? [closed]
Given the hash:
491c290affbf5436f0fc0584ccefb2
how do I construct a rainbow table to crack this password?
6
votes
3answers
212 views
How much added security do I really get with a longer key size?
Imagine I have a cipher which supports keys of 128, 192 or 256 bits. Suppose that there are no vulnerabilities in the cipher regardless of key length. I'm going to use it to encrypt something, and ...
10
votes
1answer
393 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 ...
-1
votes
3answers
182 views
find password and iv of an encoded string knowing the decoded string
If I would know the clear and encoded versions of a string could I somehow find the password and.or iv that wore used to encode it?
Encoding done with open_ssl aes-128-cbc.
0
votes
1answer
165 views
How key_derivation and key_verification functions are implemented of a 7-zip archive's encryption mechanism?
I am curious about how password recovery works for password protected files. And I want to know the exact flow of the 7-zip encryption mechanism :) !!
7-zip uses the AES-256 encryption algorithm in ...
9
votes
2answers
630 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 ...
4
votes
2answers
132 views
What steps can you take to make offline cracking of SRP harder?
In the aftermath of the Blizzard hack, what steps can I take to make offline cracking of SRP more difficult?
My question assumes that your database is already gone and that you implemented SRP more ...
5
votes
3answers
1k views
HTTP Basic auth password storage more secure than Digest auth
If you are using SSL already, it appears Basic auth is the way to go since you can perform bcrypt with the password when you store it in the database, where as Digest auth only allows md5. As we know, ...
5
votes
8answers
718 views
Does truncating the cryptographic hash make it impossible to crack?
I store password hashes in their full value for example, $h = sha256('foo') outputs 64 characters: 2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae
I store that directly in the ...
2
votes
4answers
224 views
Can public keys be a security risk when performing password-less SSH logins?
Some companies use monitoring software such as nagios or icinga. In order to perform checks on the servers, they often need password-less SSH logins.
The servers being checked put the public key of ...
1
vote
3answers
4k 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 ...
1
vote
3answers
287 views
Differences between brute forcing access versus decrypting password files or databases
I was just reading about how it's better to use bcrypt to protect passwords instead of saving password hashes in databases, and that got me thinking about other aspects that hackers work on that I had ...
3
votes
2answers
232 views
Is the password hash better when you concatenate the password and username?
Is the password hash (with bcrypt) better when You concatenate the username with password?
For example:
$this->hash($username . $password);
and
$this->hash($password);
Last time I used ...
4
votes
4answers
619 views
Is encrypting a salt value with a password/plaintext a viable alternative to straight up hashing?
The basic problem, as far as I can tell, is that hashing's flaw is that the password is in the hash. Asymmetric encryption's flaw is that the password is encrypted and can be reversed.
The posts ...
25
votes
8answers
2k views
Why would salt not have prevented LinkedIn passwords from getting cracked?
In this interview posted on Krebs on Security, this question was asked and answered:
BK: I’ve heard people say, you know this probably would not have
happened if LinkedIn and others had salted ...
3
votes
1answer
364 views
For what malicious activity can one use a computer with a high-end GPU?
I'm currently researching what malicious activities can one do with a computer containing a high-end GPU. So far the only uses I found were Bitcoin mining and password cracking. Are there any other ...
7
votes
2answers
417 views
HMAC Based Request Signing - Storing the Salt
I'm working on a (non high security) project that currently isn't live but might go live at some point.
We have a REST API (implemented using Restlet and Neo4j) running on a server and an Android ...
2
votes
1answer
1k views
Is BCrypt enough when saving a password into a database?
In order to allow users to connect to my website, I encrypt their password using BCrypt since it is one of the slowest algorithms to decrypt (making a compromised database longer to be decrypted).
...
0
votes
1answer
140 views
Stripping / appending characters from user password before hashing to conceal it forever?
I had this idea to permanently conceal user password by requiring minimum length then stripping certain characters. For example if the user password is secret123, the system will strip it down to ...
2
votes
2answers
293 views
Can key files be brute-forced like passwords?
Let's say you use a program like Truecrypt or Keepass which allows you to have a password + key file. I understand that passwords can be brute-forced/dictionary-attacked but is the same true for key ...
17
votes
5answers
1k views
What's the practical limit for rainbow-table based bruteforce?
Say we have a hash of a password. The password can be considered to be made of of totally random characters and has a fixed length of N. The hash is SHA1(password+salt), where the salt is of length M. ...
6
votes
1answer
698 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 ...
-1
votes
1answer
148 views
How Does VMWare Protect Passwords? [closed]
I am interested what features VMWare uses to protect passwords inside the virtual machine.
2
votes
3answers
411 views
What is the recomended algorithm to create a key from a password?
In my new secret document encryption utility, the key for symmetric encryption = the hash of a random salt and a user provided password.
It is necessary to have a slow hash function in order to ...
8
votes
2answers
1k views
How big salt should be?
I will be using scrypt to store passwords in my application. As such, I'll be using SHA-256 and Salsa20 crypto primitives (with PBKDF2).
Having that in mind, how big salt should I use?
Should it be ...
3
votes
1answer
468 views
Bcrypt as a key derivation function?
I read a lot of entries at stack exchange about bcrypt and why it is supposed to be better than PBKDF2 in terms of password storage.
I'm asking now if bcrypt is better than PBKDF2 in terms of key ...
4
votes
2answers
859 views
openssl_digest vs hash vs hash_hmac? Difference between SALT & HMAC?
openssl_digest vs hash vs hash_hmac
I want to use SHA512 for storing password.
Which of the above methods are best to use? Why?
What is the difference between SALT & HMAC?
I just read ...
4
votes
1answer
179 views
Thoughts on creating unscalable conditions to brute force even small passwords?
I stumbled upon something called "scrypt" which claims to add fixed time/space complexity requirements into password-based key derivation.
Quoting from their page:
A simple password-based encryption ...
12
votes
6answers
3k 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 ...
4
votes
1answer
1k views
Rainbow tables, generation and lookup, preferably using GPU
1a) What software can I use to generate my own rainbow tables, preferably software that can utilize CUDA or ATI Stream?
One of the reasons I want to make my own, is that I want to use a specific ...
5
votes
2answers
1k views
What algorithms are best be cracked by GPU?
What algorithms are best being attacked by a GPU powered password cracker?
For example, I heard that md5crypt that is being used in unix shadow file, is not the best choice for GPU cracking because it ...
5
votes
2answers
3k views
Is it possible to speed up WPA/WPA2-PSK cracking using a rogue AP?
We know that WPA/WPA2-PSK uses a PTK (Pairwise Transient Key) for each client to encrypt the communication. This PTK is generated through the process known as 4-way handshake. As told in the related ...
2
votes
1answer
976 views
Are Windows password hashes salted with the user name?
I'll readily admit I'm pretty clueless when it comes to cryptography, so there may already be some false assumptions in the question title itself :-)
Still, I "heard" that it is more secure to store ...
7
votes
3answers
414 views
It is possible that brute force attempts are successful before the worst case, correct?
When I read about a password being secure and stating that it would take X amount of week, years, etc. isn't that referring to the worst case?
What happens if the brute force method is successul in ...
10
votes
3answers
537 views
Cryptographic Security of Dynamically Generated, Non-Random Salts
So when it comes to security, when I have an idea that seems good, but no one else seems to be doing, I try to assume that I'm overlooking something obvious or otherwise significant. This is one such ...
10
votes
2answers
284 views
How much security is compromised if we accept other characters as login (other than the original password)?
I've just realised that facebook accepts 3 forms of a password:
Source:
Facebook actually accepts three forms of your password:
Your original password.
Your original password with the ...
15
votes
3answers
2k views
How would you store a 4 digit pin code securely in the database?
I'm familiar with password hashing, using salts, bcrypt etc.
But it doesn't seem like this would work to store a 4 digit pin code since the attacker could try all 10,000 combinations quite quickly. ...
25
votes
2answers
2k views
Pre-hash password before applying bcrypt to avoid restricting password length
Good practice is not to unnecessarily restrict password length, so that appropriately-long passphrases (perhaps 35-45 chars for 6/7 dicewords) can be used. (See e.g. Should I have a maximum password ...
376
votes
21answers
59k views
XKCD #936: Short complex password, or long dictionary passphrase?
How accurate is this XKCD comic from August 10, 2011?
XKCD 936: Password Strength
I've always been an advocate of long rather than complex passwords, but most security people (at least the ones ...
