Questions tagged [hash]

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.

Filter by
Sorted by
Tagged with
2
votes
3answers
1k 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 ...
2
votes
2answers
656 views

Would multiple exposed bcrypt hashes of the same UUID v4 with random generated salt be too insecure?

I'm looking into implementing an ownership check on JSON objects and want to avoid going back to the database to ensure ownership of said object/record (i.e., to prevent a user from updating an object/...
2
votes
2answers
724 views

What does it mean that Hmac is secure?

I'm not taking about general collision attack on weak hash function such as MD5 or SHA-1. I'm wondering security of HMAC which is based on weak hash function If there are key k, message m Hmac(k,m) =...
2
votes
1answer
279 views

How does an attacker authenticate to a service using just the hash of the user (after performing a “pass the hash”-attack)?

Let's say the attacker got the username and the hashed password. How can he use it when authenticating to some service in its domain with for example NTLM? How can he send the request as the ...
2
votes
2answers
2k views

Reducing hash output length [duplicate]

I am using output of (keyed) hash function to make sure the input was not modified, I store it along with input. Now output of SHA-1 is 20 bytes. Say I want to reduce the output. And have it output 10 ...
2
votes
1answer
359 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 ...
2
votes
5answers
1k views

Methods used to reverse a hash

I know that a hash is a one-way-function and that therefore there isn't a reversal function. By reversing a hash I just mean to find some plaintext that gives the hash. I think that I understand that ...
2
votes
2answers
2k views

List of vulnerable and “usable” hash functions

Searching the internet I only saw tables of encryption/hashing families and the logic. I've seen a video recently from Computerphile about breaking passwords using dictionary rules and previously ...
1
vote
1answer
1k views

encrypted lookup-keys for key-value store

I'd like to use a key-value store (cassandra, redis, ...), but I don't trust the server. The clients have a shared secret, and I'm using that to encrypt the stored values. But what is the proper way ...
1
vote
1answer
114 views

Include input data in key stretching?

Follow-up to this question: Strong PHP hashing without salt. Without entering into the details, using bcrypt without salt/pepper is a bit complex for my case, so I'm staying on a "plain loop" ...
1
vote
2answers
482 views

What if the Local Windows Cert Store is Compromised?

The diagram below illustrates chaining digital certificates up to a publicly trusted Root Certificate: I have been researching how trusted root authorities (such as GlobalSign or Verisign) are used ...
1
vote
1answer
3k views

How many possibilities can today's computers check (per second) in a SHA512 hash of a 50-byte-long random entry? [closed]

The problem I want to avoid is "brute force" attacks against a database. So if I add a 50-byte-long cryptographically random salt to my information (which I don't need to retrieve, just its hash) - is ...
1
vote
1answer
905 views

PHP: password_hash() - do I need to define the cost?

Do I necessarily need to define the 'cost' for password_hash()? Is there any default value for the cost? I know using custom salt with password_hash() is not recommended. How much time does it take ...
1
vote
2answers
208 views

Should hashing hashed hashes colide or not?

Since key stretching basically boils down to hashing hashes over and over again (where salt, pepper and password individualize the hash function, but the principle remains the same), I wonder about ...
0
votes
3answers
1k views

Testing a password for similarity to previous hashes

This question is a follow-up to a comment by Tobias Kienzler to an answer to "What is the purpose of the “Password minimum age” setting?". Consider a password policy that new passwords cannot be ...
0
votes
1answer
331 views

PBKDF2 constants

I recently found this PBKDF2 code: <?php /* * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm). * Copyright (c) 2013, Taylor Hornby * All rights reserved. * * ...
0
votes
1answer
150 views

Storing third party auth info; Is this secure?

I have a feature request to connect my PHP web-app to the users mail server. I have usually strayed away from this type of work as it will mean storing the users email passwords. My question: is it ...
0
votes
2answers
121 views

Is there a cryptographic function that generates a reconizable visual pattern?

I have to build a system that will ultimately print a pass allowing access to a building. The validation of this ticket will be done manually (it can also be automatic but that's not likely at this ...
0
votes
2answers
401 views

Is my understanding of SHA1 correct?

My understanding is that SHA1 is a 'shared' hashing algorithm. As in, if somebody on the other side of the world on an entirely different system runs a string through SHA1, it will result in the same ...
0
votes
2answers
115 views

Is my Password Hashing Secure or not?

I have recently created a code for hashing password. Can you please give your advice over the security of my code? The function takes a password, then converts it to a number. #include <string> ...
0
votes
1answer
266 views

(Why) does an encrypted MS Office 2010 Spreadsheet (need to) have the password hash “written down”?

To my naive mind, it seems like the encryption of a document with AES should go like this: HumanPassword ---|hash|--> key ---|AES|--> Ciphertext plaintext|--^ And the ...
0
votes
2answers
587 views

How can I identify this hash? [closed]

I'm trying to decrypt my router's root password, since I only have access to a simple admin account that doesn't have root privileges. Here is the passwd file: 0:F.bCrWv/Oxp6.:0:0:root:/home:/bin/sh ...
0
votes
2answers
240 views

How do you overcome the problem of the salt being public and known by the attacker? [duplicate]

I believe that when adding a salt to the password you need to store the values so you can compute the hash again. But, what does happen if the attacker get the salt? How is it possible to add value ...
-1
votes
1answer
138 views

Unconditionally Secure Authentication

I'm trying to add the authentication for my One-Time Pad implementation. I know that to provide Unconditionally Secure Authentication I need to use the One-Time MAC authentication. But I don't ...
-1
votes
1answer
81 views

Shouldn't multiple images always exist even in most powerful hashing algorithm?

I have a confusion in mind that since in hashing we transform a large string into a smaller fixed size string, so its unlikely that any large string has a unique hash. There had to be collisions and ...
-1
votes
2answers
138 views

Website says my new password can't be used because it is the same as an old one [duplicate]

What are the risks of storing (in hashes I guess) all the old passwords? Why would a company chose to not delete old passwords? Why not let users reuse old passwords?
-2
votes
2answers
236 views

When should a password be hashed? [duplicate]

I develop a Smartphone App and have a little question: When should I hash the user passwords, on the device or upload them in plain text and hash them on the server before stored in the database?