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
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 ...
2
votes
1answer
62 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 ...
3
votes
1answer
139 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 ...
5
votes
2answers
100 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 ...
6
votes
3answers
284 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 ...
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:
...
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 ...
3
votes
2answers
246 views
Does it make any difference of the order Hashing and Encrypting in terms of security?
I am implementing a password vault program with java. I have programmed a triple DES for encryption and a SHA256 for hashing.
My question is would it make any difference if I first hash the raw data ...
1
vote
2answers
116 views
How high is the entropy of this salt-generating code? (No code-reading actually necessary)
What is the best method?
Assumption: I have a function that generates a number of medium-high entropy bytes
Step1:
I generate 3 of these medium-high entropy bytes.
Step2:
I hash these bytes using a ...
3
votes
5answers
332 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 ...
2
votes
1answer
180 views
sha-512 vs sha-3? [duplicate]
Does the new SHA-3 Keccak hashing algorithm offer any benefits from SHA-512?
"Even worse, none of the SHA-3 candidates is significantly better. When SHA-3 is announced, I'm going to recommend that, ...
0
votes
4answers
221 views
Is using the md5 hashing algorithm as method for authorization in an HTTP POST request unsafe?
I am creating a page on a website that will show a user some authorized information from another website, and that website uses a combination of the user's user-number and a secret passphrase hashed ...
5
votes
3answers
229 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
115 views
Easy protocol for email authentication
I'm cooking up a very simple system to send commands to a remote server via email. Everytime an email is sent to do_something@mydomain.net, the server runs a python script that does something ...
1
vote
5answers
290 views
Is SHA-1 encryption?
I have read that SHA-1 is a cryptographic hash function. On an exam, SHA-1 was given as a possible one-way encryption algorithm. Does SHA-1 require a key as input? Is a key required to qualify as ...
3
votes
3answers
271 views
Hash Function Xor
For a hash function what is the best secure method, XOR or Concatenate:
h(data1 XOR data2 XOR data3 XOR data4) ? or use h(data1||data2||data3||data4)?
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". ...
2
votes
1answer
462 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 ...
2
votes
3answers
357 views
rsa encrypted hash == rsa signature
$ echo -n "1327943823" > test_ok.txt
$ openssl dgst -sha1 -binary -out test_ok.sha1 test_ok.txt
$ echo "GURbsl4CFPCG83RCZxsEpoRleXicXQhH1OC4Fk77b7EMj2g8aHUhD/L+sm
...
2
votes
1answer
100 views
Seeding GPG keygen with a hashed secret [duplicate]
Possible Duplicate:
Tool for public key cryptography where password is the private key?
I was wondering if you guys could clue me in to potential problems with using a hashed password as ...
-5
votes
3answers
373 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 ...
2
votes
2answers
609 views
Should we start using SHA-3? [duplicate]
Possible Duplicate:
What is SHA-3 and why did we change it?
SHA-3 has been finalized! So, what does secuirty.se think about the new hash funciton? Should we start replacing all uses of ...
4
votes
1answer
56 views
Standards for CA cert revocation and time-constrained cryptographic algorithm parameters
I'm working on software that will be in use for foreseeable future (15 years+) that will need to validate XAdES-A signatures (long term archival, similar to PAdES-A, but for XML). That means, it will ...
1
vote
1answer
194 views
Can I combine two of SHA-3 candidates cryptography hash functions and obtain more secure Algorithm? [duplicate]
Possible Duplicate:
Are different hash algorithms ever used together?
For example, Is possible to combine (Concatenate or Chain or XOR) Skein SHA-3 candidate with Grostl SHA-3 candidate to ...
9
votes
2answers
588 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 ...
2
votes
1answer
1k views
Is PBKDF2 only SHA1 in C#?
I can't find a way of specifying the hashing algorithm used by the PBKDF2 (the Rfc2898DeriveBytes class) implementation in C# System.Security.Cryptography.
It seems to be just SHA1. Am I missing ...
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 ...
6
votes
3answers
307 views
How secure is HTTPS with weak ciphersuites?
Today I came across the website https://mtgox.com/, which claimed to be secure because of the Verisign certificate. I checked the certificate out of curiosity (it's the first thing they claim, let's ...
-1
votes
2answers
109 views
Should I use salt to authenticate data?
I have a client and a server. The client makes a request containing userId, cardId, position (on the card)
A hacker could just do the same http request with the next position. So I think about ...
3
votes
2answers
119 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
8answers
679 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
6answers
191 views
Is it okay to wrap a cryptographic hash with MD5 for storage?
Is there any security issues if you wrap your cryptographic hash with MD5 for storage purposes?
For example:
$hash = md5(hash($password,$salt,$rounds));
Note: hash() uses scrypt or bcrypt or pbkdf2 ...
1
vote
2answers
493 views
Is there an index of all md5 collisions?
I am about to build a caching system based on md5 to generate file names out of lists of natural numbers. The inputs would be groups like: 1,18,94,100,266,1854.
I know there are some collisions in ...
1
vote
3answers
3k 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
277 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
225 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 ...
2
votes
4answers
250 views
Fingerprinting Hash Function
For the purpose of fingerprinting data with the least chance of collision will combining the length (as a 32 bit unsigned integer stored in addition to the hash) of the input data and/or sampling a ...
4
votes
4answers
586 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 ...
6
votes
2answers
400 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 ...
-1
votes
1answer
152 views
How to find the encryption of a cipher and apply it to another key [closed]
I am very new to cryptography so please help me out with this one
I have a Question Key-1 which + some encryption gives Answer key-1. I have to find the encryption to apply it to another Question ...
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
137 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 ...
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. ...
3
votes
3answers
169 views
Does the hash change the security of the Secure Remote Password protocol?
I'm implementing the Secure Remote Password protocol, and similar to this question, I'm wondering if I can use the SHA-512 hash function instead of SHA-1 currently being used. Would this help improve ...
11
votes
2answers
2k views
What is the difference between a Hash Function and a Cryptographic Hash Function?
I mean, is it just a matter of "how dificult is it to reverse the function with the current technology"?
Or is there a mathemathical concept or property that makes them diferent?
If it is a matter ...
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
444 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
278 views
Zero padding in HMAC
Section 2 of RFC 2104 defines the key used in HMAC should be padded with zero bytes up to the block length of the underlying hash algorithm.
Isn't this a potential security vulnerability since any key ...
