Tagged Questions

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.

learn more… | top users | synonyms (1)

-1
votes
1answer
502 views

Global salt vs salt-per-password [duplicate]

Possible Duplicate: Password Hashing add salt + pepper or is salt enough? Any risk in using the same salt for several hashes on a user? It's known that all password hashes need to be ...
1
vote
1answer
1k 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 ...
3
votes
1answer
193 views

How should I store a password to allow people to enter single characters from it? [duplicate]

Possible Duplicate: How do some sites (e.g. online banks) only ask for specific characters from a password without storing it as plaintext? Some banking applications ask for random letters ...
2
votes
2answers
990 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 ...
8
votes
2answers
655 views

Is there more to password hashing?

You have a plain text password and salt. The plain text password is assumed to be securely random and only known by the user and the salt is no secret and not necessarily unique but stored alongside ...
12
votes
2answers
3k views

With PBKDF2, what is an optimal Hash size in bytes? What about the size of the salt?

When creating a hash with PBKDF2, it allows the developer to choose the size of the hash. Is longer always better? Also, what about the size of the random salt? Should that be the same size as the ...
1
vote
1answer
97 views

How to verify that a clientside-generated object is genuine?

I know that general best-practice states not to trust anything generated by the client. With that in mind, I want to write an HTML5 app that utilises the browser to generate various objects ...
54
votes
5answers
15k views

Is sending password to user email secure?

How secure is sending passwords through email to a user, since email isn't secured by HTTPS. What is the best way to secure it? Should i use encryption?
5
votes
2answers
355 views

Can a HSM be used to make password hashing stronger?

Say a database server has a HSM which is in use for encrypting (reversibly of course) credit card numbers. Is there any way a HSM could be used to add strength to a password hashing scheme? (Or are ...
-2
votes
2answers
334 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 ...
8
votes
4answers
601 views

How can we factor Moore's law into password cracking estimates?

How would we go about factoring Moore's law into exceedingly long password cracking estimates? Let's say we've got a 12 character password containing mixed-case alpha characters and numbers, i.e. ...
4
votes
3answers
14k 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 ...
5
votes
3answers
584 views

Trying to understand password hashing

I am trying to get a grasp of password hashing. Back in the days it seemed so simple, just MD5(password + salt) and you are done. Then md5 was proven to have collisions so people started moving to ...
2
votes
3answers
115 views

Clarification on an email about a security breach

I got the following email from a forum I was subscribed to: It is our duty to inform you that there has been a security breach on the server that Doom10 was being hosted on. It doesn't seem like ...
7
votes
3answers
9k views

How to crack password hashed using SSHA?

Is it possible to crack a password hashed using SSHA if I know the salt? How can I do it?
11
votes
3answers
745 views

Does the salt need to be unique or not predictable?

I always thought that salts is simply used to prevent rainbow tables to be used. Other have suggest they should be unique on a per account basis. Currently i have been using a config file to use as ...
15
votes
7answers
703 views

To salt, or not to salt? [duplicate]

Possible Duplicate: Why is using salt more secure? Why would salt not have prevented LinkedIn passwords from getting cracked? Recently I decided that I wanted to learn more about web ...
2
votes
4answers
710 views

How password hashing is useful in MITM attack?

Even though I read a lot about hashing and how passwords are protected, I am still confused about it. If passwords are hashed at client side, it will be useless because it can be sniffed and used by ...
193
votes
6answers
24k views

How to store salt?

Nowadays, if we expect to store user password securely, we need at least do the following thing $pwd=hash(hash($password) + salt) then store $pwd in your system instead of the real password. I have ...
3
votes
5answers
403 views

PCI-DSS and salt storage

PCI-DSS states the following: 3.5 Protect any keys used to secure cardholder data against disclosure and misuse I have a service which stores a salted bcrypt hash of the user's PAN. Assuming the ...
4
votes
5answers
549 views

Can hash functions be used with CTR or OFB mode?

I have been writing a class that encrypts and decrypts with block ciphers. I want to use Counter Mode(CTR/CM). We know that Counter Mode generates a keystream basing on counters, then XOR the ...
-2
votes
1answer
449 views

What encryption hash function I should use for password securing? [duplicate]

Possible Duplicate: How to securely hash passwords? What is the best encryption algorithm? MD5, SHA1, SHA2 or maybe something else? Can you explain me why?
5
votes
4answers
478 views

How to upgrade the hashing method of a live database without compromising security?

I'm working on an Intranet project that is accessible from the outside. The password are stored in a Sql Server database in the normal Hash and salt method. The problem lies in the hashing algorithm. ...
1
vote
3answers
232 views

Does this kind of hashing exist?

Let's say you have two user defined strings, X, Y and you want to hash them into the hash Z. That is what most websites would do, X is the user's password and Y is the salt. It takes a lot of time to ...
2
votes
3answers
620 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 ...
-1
votes
5answers
449 views

Is this password hashing method secure?

I have made a custom hashing method to help make my users' passwords more secure if the database will be leaked. The encryption method is like this: A method takes an input of 1 character, gets the ...
2
votes
3answers
1k views

When to use the different types of Encryption / hash algorithm?

I'm studying for CISSP and know they will ask what type of encryption to use in different situations. Does such a list exist or is there a general rule of thumb to use?
0
votes
2answers
614 views

Knowing Hash Algorithm from Hashed String

I found an application which stored its password in database as: A69F00623BE6B8 It's a 14-character string length. How do I know this password algorithm? What's the keyword to describe this ...
3
votes
2answers
353 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 ...
1
vote
4answers
401 views

Are there vunerabilities with this authentication mechanism?

I am trying to come up with a way to implement token-based authentication for a REST API without the need for SSL. The goal here is to avoid sending any sensitive information across the wire. I was ...
1
vote
2answers
453 views

Hash, encryption of file… key? Need help [closed]

So my previous question was with some help on pcap files as I am doing a security course and we have a challenge to figure out what was going on in our network. Now one of the files I retrieved is an ...
8
votes
3answers
4k views

Is a HMAC-ed password is more secure than a bcrypt-ed or scrypt-ed password?

Given an option , which one should I choose , a HMAC for storing a password securely or a bcrypt or scrypt library?
1
vote
0answers
304 views

what is this hash type? [closed]

Actually I have this hash but I don't know what cryptographic hash function generated it. 4753305A7A673D7A5A442156 I know password is 12345678 I extracted this pass from PLC device Mitsubishi
2
votes
3answers
1k views

Recompute Rainbow table with salt?

So, as I understand it, you prepend a password with salt before you hash it so that the resulting hash can't be used with a rainbow table to find the original password, as you could if the password ...
33
votes
3answers
3k views

Security Review - password_hash implementation for PHP

I'm currently working on a "helper function" for PHP's core to make password hashing more secure and easier for the majority of developers. Basically, the goal is to make it so easy, that it's harder ...
0
votes
6answers
507 views

Using passwords made of words

People say don't use passwords in the dictionary but if you use two words isn't it alright? Dictionaries have at least 10,000 entries so just two words will be 100,000,000 possibilities (and that's ...
10
votes
3answers
6k views

What's the advantage of using PBKDF2 vs SHA256 to generate an AES encryption key from a passphrase?

I'm looking at two comprable pieces of software which need to encrypt data on disk using a passphrase. One uses PBKDF2 to generate the encryption key from a passphrase, while the other uses two rounds ...
6
votes
3answers
622 views

Are online hash calculators dangerous?

I was about to use an online MD5 checksum calculator when I realized that my result could be added to a database. This is significant because the string I was going to type in was my bank password. ...
7
votes
3answers
671 views

How should I choose a difficulty factor for my password hashing function?

Assuming that I'm doing password hashing properly and using bcrypt, scrypt or PBKDF2, how should I go about choosing an appropriate difficulty factor? i.e rounds for bcrypt, iterations for PBKDF2 and ...
2
votes
4answers
360 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 ...
21
votes
5answers
919 views

Hashed password storage with random salt

Ever since I've been making sites that require a user to log in with a username and password I've always kept the passwords somewhat secure by storing them in my database hashed with a salt phrase. ...
3
votes
3answers
355 views

What pros and cons are there to a one-time random salt between client and server?

In researching on best practices in hashing passwords using a salt I came across a presentation on slideshare. The approach outlined is as follows Client requests login page Server-side code ...
-4
votes
1answer
2k views

efficient 16 bit hash [closed]

I'm looking for a way to make a 16bit ID out of approx 100 bits of data. The solution should be easy to implement, or should already be implemented in c++, should be quick to evaluate, and most ...
18
votes
4answers
1k views

In hashing, does it matter how random a salt is?

I recently had a comment made to me in an online discussion after I'd stated that randomness in a salt doesn't matter -- and I got the following response: Salts may not have to be "secure," but ...
-5
votes
2answers
3k views

Is AES slower to encrypt than MD5?

Is this the right interperation of this diagram: http://www.cryptopp.com/benchmarks.html AES/CCM MiB/Second:61 Cycles Per Byte:28.6 MD5 MiB/Second:255 Cycles Per Byte:6.8 And does that ...
5
votes
4answers
2k 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 ...
29
votes
8answers
4k 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 ...
2
votes
1answer
105 views

What is the meaning of 'adaptative' and 'over time it can be made slower' in the context of the bcrypt algorithm?

I'm reading the wikipedia definition about bcrypt but I don't understand the meaning of 'adaptative' and 'over time it can be made slower'. Can someone explain what they mean in this situation?
21
votes
5answers
2k 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 ...
17
votes
8answers
13k 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 ...