A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.
4
votes
2answers
75 views
Do SSD's offer significant performance boost for Scrypt?
Being a memory intensive hash, I was wondering if SSD's offer any appreciable performance boost for brute force attacks.
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 ...
-1
votes
3answers
121 views
Salting in encryption (rather than hashing)
I am aware of the benefits of adding a salt to values that are hashed using a one-way function. Is adding a salt to a value that is being encrypted (using symmetric encryption) considered to be good ...
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 ...
2
votes
4answers
168 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 ...
2
votes
1answer
134 views
What is the collision chance of a 128-bit hashing function if it is always fed with 256-bits of data?
I mean "normal" collisions not based on any attack.
How do i calculate it?
13
votes
7answers
3k views
Why do people still use/recommend MD5 if it is cracked since 1996?
It's still commonly recommended way of hashing passwords, even if it's insecurity had been proven in 1996
Therefore we suggest that in the future MD5 should no longer be implemented in ...
4
votes
2answers
92 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 ...
4
votes
1answer
78 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 ...
5
votes
1answer
86 views
Is the execution time for bcrypt independent of the length of the input string?
Is the execution time for bcrypt independent of the length of the input string?
i.e.
Should the execution time of
bcrypt.hashpw('input_string', bcrypt.gensalt(12))
and
...
0
votes
1answer
88 views
How secure is my private key in the Windows Digital Certificate store?
Many files we download don't have digital signatures. Files may get infected or someone may intentionally modify them on our hard disk.
So I wrote a simple file hashing program in c# that creates a ...
2
votes
0answers
55 views
Knowing a valid salted hash for an unknown secret, is it possible to compute another valid hash? [migrated]
H(s,r)=d is a function that hashes the string s with a salt r, giving the result d.
Hashing functions are not injective, so there isn't a reverse function H'(d,r)=s.
Therefore to prove that d is a ...
0
votes
3answers
102 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 ...
3
votes
5answers
326 views
The security level in hash function
What is the difference in security between using part of message digest hash function or all the message digest hash function? and is there any equation can calculate the security for part or whole ...
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 ...
114
votes
11answers
14k views
How to securely hash passwords?
If I hash passwords before storing them in my database, is that sufficient to prevent them being recovered by anyone?
I should point out that this relates only to retrieval directly from the ...
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, ...
2
votes
1answer
61 views
Hash extension(padding) attack
I recently came across this website talking about sha1 padding attack.
http://www.vnsecurity.net/2010/03/codegate_challenge15_sha1_padding_attack/
After reading here are some of my doubts:
How ...
196
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 ...
3
votes
1answer
136 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 ...
4
votes
2answers
105 views
Truncating the output of SHA256 to 128 bits
suppose we need/prefer 128 bit hash output. for example to generate a 128 bit encryption key or, in other applications (e.g. file integrity verifications), to consume less storage space.
i don't know ...
0
votes
4answers
78 views
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 ...
0
votes
0answers
21 views
LT codes with Homomorphic hashing [migrated]
I have been working on a project implementing LT codes with Homomorphic hashing (inspired from http://blog.notdot.net/2012/08/Damn-Cool-Algorithms-Homomorphic-Hashing and ...
11
votes
1answer
218 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 ...
16
votes
3answers
5k views
Is SHA1 better than md5 only because it generates a hash of 160 bits?
It is well known that SHA1 is recommended more than md5 for hashing since md5 is practically broken as lot of collisions have been found.
With the birthday attack, it is possible to get a collision ...
3
votes
3answers
595 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 ...
6
votes
3answers
305 views
Is Using MD5 Sufficient Reason to Reject This Payment Processor?
I'm evaluating a credit card processor[1], and I noticed they are using MD5 as part of a salted hash algorithm to protect a secret key. Since I know MD5 is generally considered broken, this feels like ...
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 ...
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 ...
0
votes
1answer
63 views
what does GUID have that a whirlpool, md5 or sha2 hash dont
I'm trying to understand the use of GUID and what has always left me wondering is what's so special about them that I should consider using them instead of rolling my own type of unique id.
In other ...
6
votes
2answers
609 views
Stretching a hash, many iterations versus longer input string
I have been reading up on various password hashing schemes, for example the SHA-based Crypt proposed by Ulrich Drepper and used in some Linux versions.
A recurring theme here is to 'strengthen' or ...
23
votes
5answers
1k views
How does hashing work?
I have been interested in Information Security. I was recently introduced to the idea of hashing. What I currently understand about hashing is that it takes the password a user enters. Then it ...
2
votes
1answer
85 views
Securely store two values per user in SQL
I have come across the need in my web app to store two values for each user. These values would need to be retrievable from a value stored in a URL. I would prefer to store neither of the values in ...
-5
votes
3answers
370 views
create a variants of MD5
I have also asked similar q here :
To create a variants of MD5, I made following changes :
MD5 uses a non-linear sin(i)* pow(2,32) ----> i plane to use cos(i)*pow(2,32)
Instead ...
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 ...
18
votes
5answers
710 views
Is it possible to increase the cost of BCrypt or PBKDF2 when its already calculated and without the original password?
I just wanted to know if you can increase the cost (iterations) of those two algorithms off-line.
I want to increase the cost every year of my users passwords.
One solution is to recalculate them ...
11
votes
4answers
453 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 ...
3
votes
5answers
122 views
Expanding/Inverse Hash function
First off, before I ask my question, let me explain what I am NOT asking. I am NOT asking for a way/method to reverse a hash output; by definition, a hashing function is one-way.
Is there such a ...
6
votes
1answer
101 views
Encrypting short identifiers?
I am developing a webapp that does not reveal record count, because it hides the primary key. I am looking for a better way to do this.
My favorite idea is to encrypt the ID itself with a block ...
8
votes
2answers
72 views
PINsentry PRNG and Bank Cards
My bank provides me with a device similar to this:
The device is essentially a PRNG, presumably based on the date/time of it's internal clock, synchronized with the bank servers.
To generate a pin ...
13
votes
4answers
2k views
How quickly can these password schemes really be beaten?
If you use a quick hashing algorithm like MD5 or SHA-1 to hash passwords and you don't use any salt at all, how quickly could one expect a hacker to find my password out?
If I use a truly random salt ...
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
972 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
200 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 ...
5
votes
2answers
97 views
NTLMv2 resistance to bruteforcing
I have a question regarding NTLMv2 resistance to password bruteforcing.
I know that some modern graphic processors (like Radeon 6990) are able to calculate billions hashes per second and crack NTLM ...
-2
votes
2answers
200 views
How to secure passwords when site is opensource [duplicate]
Possible Duplicate:
How to securely hash passwords?
How can I store passwords to have them secure? Right now the site use md5 md5, I was thinking about sha1+salt but if the source code for ...
5
votes
3answers
278 views
Is there a length beyond which increasing password length provides no additional security?
Assuming that the password is stored hashed and salted, and that it is a string of random characters, is there a point where adding to password length doesn't add security?
Since the hash will have a ...
-5
votes
4answers
3k views
How to decrypt LDAP passwords Hashed as MD5? [closed]
I am doing a penetration test, and i would like to know if i can decrypt passwords stored in LDAP. i tried some sites decrypt MD5 , they give me error message tells that the input is not MD5.
Could ...
1
vote
1answer
38 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:
...
