Tagged Questions
2
votes
2answers
34 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 ...
2
votes
4answers
170 views
When salting and hashing passwords, any advantage to including password length?
In this answer, Gilles says (emphasis mine):
There's no need to hide the salt from the attacker: it needs to be unique (and not derived from the password) but it doesn't need to be more secret ...
22
votes
7answers
3k views
Is salting a hash really as secure as common knowledge implies?
(I did search on this topic, but I found no complete question/answer that addressed it, or even good portions of questions that might be relevant.)
I'm implementing a salt function for user passwords ...
4
votes
1answer
80 views
Could a password hash that's prone to more collisions provide better overall security?
Website security breaches seem to be a common occurrence, giving the attacker password hashes that he can conduct a brute force attack against, often given him a list of passwords that will work on ...
4
votes
2answers
94 views
HMACSHA512 versus Rfc2898DeriveBytes for password hash
We are currently using HMACSHA512 in .net, with a 128Char (64byte) validation key
The salt is 64 char randomly generated string.
We allocated 2048 length on the database for the hashed base64 string ...
0
votes
3answers
105 views
Why one time passwords using nested hash chain are not used?
I am wondering, why web sites do not use one-time passwords generated by hash chain. By that I mean that a client chooses a secret and after being salted, he applies some secure hash function F() on ...
0
votes
2answers
76 views
Does hash solve passwords in parts?
From an answer this earlier question: Does adding dictionary words to passwords weaken them?
"...you have no way to recognize it as a password before testing it
(against a hash or an online ...
3
votes
1answer
75 views
Are there any uses of having a non-deterministic salt value for hashes?
So I've been toying with the idea of having non-deterministic salt values for hashes.
Let me explain what I mean:
Basically, I applied some properties from Bitcoin including a "difficulty" (ie, ...
3
votes
1answer
138 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 ...
11
votes
1answer
219 views
“Please Enter Nth Character” without HSM
This question has been asked a few times, but always in the format
"How does examplewebsite.com implement their 'please enter xth yth and zth characters of your password' function?"
And the ...
5
votes
3answers
2k views
With ASIC bitcoin miners, should SHA256 be considered insecure for password hashing?
I'm sure everyone here has seen the rise and further rise of bitcoin. The process used for mining bitcoin is basically "let's brute force an SHA256 hash that is less than this amount"
That being ...
11
votes
4answers
455 views
Handling passwords in a web application
I am trying to learn how a secure web application is developed. Particularly, I am unsure of how passwords are sent from the client to the server. For a typical user/password login form. If the client ...
1
vote
1answer
201 views
Use brute force to mitigate brute force
Just an idea I had, and I am sure there is a lot of material about this subject, so I am looking for a pointer as to where I can find more information.
My idea is this...
When storing a password in ...
20
votes
8answers
1k 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 ...
17
votes
4answers
976 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 ...
1
vote
1answer
39 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
1answer
144 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 ...
10
votes
2answers
1k 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
1answer
107 views
Recover password or password hash from locked acount.
I have a locked administrator account. Other accounts is unlocked, but it has no rights. I want to get a password from the locked account, or maybe password hash, if possible.
6
votes
3answers
229 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
3answers
194 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 ...
3
votes
2answers
189 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, ...
6
votes
2answers
228 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 ...
9
votes
3answers
1k 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 ...
2
votes
2answers
257 views
Why doesn't Microsoft implement salt on users passwords in Windows?
Pretty straightforward - So we use rainbow tables to get passwords of users out of hashes. So why won't Microsoft implement salt on the passwords in Windows to be hash(password+salt)?
Won't this ...
0
votes
0answers
34 views
Database hash for password field [duplicate]
I'm using a mysql database and am looking for a cryptographic hash method for a password with salt added to it. What would be the best hash method for this problem?
2
votes
1answer
323 views
Using John the Ripper to crack SHA hash w/ partial knowledge
Group, I have a SHA1 hash that I would like to brute-force. I have knowledge of several characters before and after the password (ie, if the hash is derived from "xxxpasswordyyy", I know both xxx and ...
3
votes
2answers
94 views
Fixing the high-bit problem in PHP's crypt() implementation
I'm working on a site that has to have compatibility with older versions of PHP, which suffer from a high-bit issue in the Blowfish crypt() implementation. Essentially, non-ASCII characters are not ...
5
votes
3answers
228 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 ...
2
votes
2answers
349 views
Salted hashes vs HMAC?
Most of discussions involving access credentials include references to "hashing salted passwords". Is this another way to referring to the HMAC algorithm or a totally different operation? Different or ...
3
votes
2answers
266 views
How does processor architecture affect password hashing speed?
Does hashing speed vary significantly using different architectures (x86 vs ARM)?
Scenario
I am investigating the possibility of using a cluster of Raspberry Pi for cracking passwords hashed with ...
1
vote
1answer
195 views
I've heard that salt is not meant to be secret, but what if I made it secret? [duplicate]
Possible Duplicate:
Password Hashing add salt + pepper or is salt enough?
How to store salt?
Ok I have been studying a lot about password hashing lately. And I have a few questions. So I ...
3
votes
2answers
200 views
is it easier to get the original password if you have multiple hashes of it?
Most users tipically use the same password for multiple applications. Let's say all of these applications hash the password in some way. Would it be easier for an attacker to get the original password ...
3
votes
0answers
275 views
Can an attacker guess my password length from a hash? [duplicate]
Possible Duplicate:
Possible to detect password length from hash? Is doubling your password adds more security?
Considering I do not provide him any personal information relating to it, are ...
3
votes
4answers
186 views
When hashing passwords, is it okay to store the algorithm used right there in the database?
Since hashing password has become a hot topic recently, it is only natural to expect things to change and assume that some time down the road you might want to replace/tweak the algorithm used in your ...
1
vote
3answers
163 views
Is it a good idea to have a “master” password?
Though I do have a good memory of passwords, it is quite impossible to have one password per application. Yet, it should be... My current way to deal with passwords is to have five passwords and to ...
-2
votes
3answers
147 views
What's the use of making users use digits, uppercase-lowercase combination password if the passwords are hashed?
Some websites, even the StackOverflow asks for atleast 1 digit, 1 uppercase character in the password so my question is does this really matter when the developer uses 1 way encryption algorithm to ...
4
votes
2answers
824 views
openssl: recover key and IV by passphrase
A large amount of files were encrypted by
openssl enc -aes-256-cbc -pass pass:MYPASSWORD
Openssl should derive key+IV from passphrase. I'd like to know key+IV equivalent of that MYPASSWORD. Is ...
2
votes
7answers
396 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 ...
2
votes
2answers
167 views
In this example why do they hash a randomly generated piece of salt before hashing it with the password?
From here, in the code return substr(sha1(mt_rand()),0,22); what is the point of taking the sha1 value? It is appended to the password and together they are hashed using Blowfish. Why not just append ...
1
vote
3answers
1k views
Is bcrypt better than scrypt [duplicate]
Possible Duplicate:
Do any security experts recommend bcrypt for password storage?
I'm no security expert and do not pretend to be that's why I'm asking here. I write many PHP based ...
8
votes
4answers
312 views
How to evaluate the strength of a hashing algorithm?
At work the hashing algorithm we use for passwords appears to be bespoke. Obviously that's a pretty bad idea, but the management don't seem bothered.
The algorithm always produces 20 character long ...
3
votes
2answers
116 views
Doesn't adding requirements to a password, such as must contain 2 digits, decrease the strength? [duplicate]
Possible Duplicate:
Doesn’t imposing a minimum password length make the password weaker by reducing the number of possible combinations?
Doesn't any constraints added to a password policy ...
198
votes
9answers
20k views
Is my developer's home-brew password security right or wrong, and why?
Our developer, let's call him 'Dave', insists on using a home-brew script for hashing passwords. See Dave's proposal below.
We have already researched and adopted an industry standard protocol using ...
0
votes
1answer
141 views
Password protection of encryption and signature keys
I would like to store encrypted backup of text files on my computer. I'm developing a python script using Pycrypto to achieve that, based on this code to use the library. (current code)
The basic ...
2
votes
5answers
164 views
Is there value in storing passwords in their own table with encrypted or hashed keys?
The usual method for simple sites is to store a hash of a user's password right in their user record.
What if the password field is removed from the user table, and a password table is created? The ...
17
votes
7answers
2k views
Why don't people hash and salt usernames before storing them
Everyone knows that if they have a system that requires a password to log in, they should be storing a hashed & salted copy of the required password, rather than the password in plaintext.
What I ...
3
votes
3answers
619 views
Choosing a session ID algorithm for a client-server relationship
I am developing an application which has a client-server relationship, and I am having trouble deciding on the algorithm by which the session identifier is determined. My goal is to restrict ...
2
votes
6answers
270 views
Does shuffling a hashed password increase its security?
I am making a web app and I'm now stuck on making the login secure. I'm thinking of adding a salt to a user-inputted password and then hash it. (md5 or sha for example)
and then I will reshuffle the ...
60
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". ...
