Linked Questions

17
votes
3answers
1k views

Is using slow password hashing on the client side easier attackable than on the server side?

As we know, one should use a slow password hashing algorithm instead of a fast one for storing passwords, to hinder brute force attacks when the database is compromised. The problem with this is that ...
12
votes
3answers
6k views

What is pre-image resistance, and how can the lack thereof be exploited?

What is "preimage resistance", and how can the lack thereof be exploited? How is this different from collision resistance, and are there any known preimage attacks that would be considered feasible?
8
votes
4answers
690 views

Can I determine if a user has the wrong symmetric encryption key?

We're using the Objectivity/DB object database with a custom encryption plugin that encrypts serialized objects on disk. Encryption uses AES with a shared secret key held by all users. I would like to ...
4
votes
2answers
649 views

A patched SHA1 attempt for password verification

This is a classical scenario: For our web based authentication platform we have a username and a password field. User enters these values and presses Log In. The browser gathers the user data, ...
3
votes
3answers
662 views

How can mega store my login details and still be secure?

I understand how Mega's encryption works. For a quick summary of all those in the future looking for an answer on this... here is how it works: Upon first signing up for an account you make a ...
3
votes
2answers
770 views

Key derivation from a random seed

The main problem is to use a block cipher to generate a random key. I would like to generate 256-bits key which can be as random as possible. I generate it in the following way: Pick a plaintext ...
2
votes
2answers
263 views

Idea for user/pass hashing to prevent rainbow tables, would it work?

I'm very new to cryptography (and security in general, for that matter), but I had an idea that I'm sure is very flawed, but is worth asking. If a computer user, online account, etc, needs to verify a ...
2
votes
1answer
513 views

Question regarding multiple SHA-256 rounds on a Bitcoin Brain Wallet passphrase…

I am attempting to come up with a way of memorizing a seed that could lead to any number of brain wallets for bitcoin. I need multiple wallets because a) I don't want all my eggs in one basket, and ...
1
vote
1answer
533 views

Key-size of encryption method

Is there a definied keysize to be used with the "AES_256-CBC" method in PHP, and what is the size? Some background: I want to store encrypted text into a PostgreSQL database. The user who posts the ...
3
votes
1answer
175 views

salting with password hash to improve security?

Would something like the following improve security (against rainbow attacks, not brute force)? Assume that $P$ is a user-chosen password, and the objective is to obtain a hash $H$ for password ...
2
votes
1answer
173 views

Why don't we use bcrypt and scrypt together?

Everyone is comparing bcrypt to scrypt. Bcrypt is proven, lots of cryptoanalysis and no vulnerabilities so far, but uses very low memory. While scrypt uses a lot of memory, but it's too early in its ...
1
vote
1answer
108 views

Extension of a password hashing algorithm using Fibonacci

I am right now taking a class named Applied Cryptography and our final project is to create a password hashing method using at least one existing algorithm and then add additional steps to make it ...
1
vote
1answer
123 views

Tips on conceiving safe software messaging platform

I have a personal project in mind in which I plan to use cryptography in order to let the users be confident in the fact that, even if all data get's stolen, it would be virtually impossible to crack ...
0
votes
1answer
82 views

How to take SHA-1 safely for my particular case?

Let me ask about my toy passwords generator program X5 which I want to improve. X5 uses a secret key and a public key to generate a password.Where any public key is supposed to be known to hackers in ...
3
votes
1answer
65 views

Recommended password complexity for SSH key encryption using AES-256-CBC

When protecting SSH private keys with password-based encryption, what would be a good minimum password complexity+length standard to make cracking the password too difficult to be worthwhile anytime ...