Does shuffling a hashed password increase its security?

Question

I am making a web app and I'm now stuck on making the login secure. I'm thinking of adding a salt to a user-inputted password and then hash it. (md5 or sha for example) and then I will reshuffle the results.

eg:

$salt = "hello";
$password = "password";
$newpassword = md5($salt.$password); //lets assume the result is 1234567890

I will reshuffle the order of the hash like exchanging the first and last character then 3rd and 3rd to the last.

the result will look like:

0284567391

Does this make the password more secure? Please don't suggest some hardcore encryption stuffs. I just need something that will make the passwords secure than just having them encrypted using a cracked hash algorithm.

Answer 1

The "shuffling" you intend is conceptually a kind of encryption: you apply a secret convention on the result. This changes anything to the security only if the convention is indeed kept away from the prying eyes of the attacker -- the attacker who just plundered the database of hashed passwords, and thus had some extensive access to the internals of your server. But the server must know of the shuffling (since it applies it). Therefore, it seems rather improbable that your shuffling is unknown to the attacker. Conclusion: your shuffling is probably not useful.

What would increase security would be to use a proper password-hashing function, which includes a salt in a cryptographically sane way, and is adequately slow (i.e. made very slow through thousands or even millions of iterations). This is called bcrypt. This sort of thing must not be improvised; homegrown schemes are very rarely secure (most are deemed secure by their inventor, but reality has a tendency to be unkind to the dreams of the self-made inventors, especially in highly technical areas where success cannot be tested, in particular cryptography).

Answer 2

To make your password storage safe, you should not use MD5 or any other fast hash algorithm, instead use a key derivation function like BCrypt.

The problem with fast algorithms is, that you can calculate 8 Giga MD5-hashes per second with common hardware (in 2012). That makes it possible to brute-force a whole english dictionary with about 500000 words, in less than a millisecond!

With shuffling the resulting hash-value, you add an additional secret to the hash. This secret will increase security just as long, as it stays secret. As long as the attacker only got access to the database (SQL-injection) it can help, as soon as the attacker gains control over the server (and your code) there is no benefit at all. You could achieve the same easier by adding a pepper to the password before hashing.

BCrypt was especially designed to hash passwords, and is therefore slow (needs some computing time). With a cost factor you can adapt the needed time to future (and therefore faster) hardware.

Using BCrypt can be as easy, as using the MD5 hash function. PHP 5.5 will have it's own functions password_hash() and password_verify() ready, to simplify this task. There is also a compatibility pack for PHP 5.3/5.4 available, downloadable at password_compat.

Answer 3

If you're looking for "more secure," you should use Blowfish or similar using the crypt(); function.

Swapping values should make a simple hash like md5 more secure, but assuming someone has already stolen your hashes, who is to say they don't already know that your application swaps characters in the hash? They would then un-shuffle your hashes and break them easily (assuming a hash like sha1 or md5) with an online tool.

tl;dr, use crypt(); instead and pick good algo and salts.

Answer 4

I'm gonna make this one short and sweet.

First, check this link out: http://crackstation.net/hashing-security.htm

Second, just use PBKDF2/bcrypt and a long salt. You'll be safe with that. Engineering your own type of manipulation, encryption, or hashing is almost never a good idea.

Answer 5

First of all stop using md5 as hash function for hashing passwords. Nevertheless it is not broken, but it suffers from variety of weaknesses. Use SHA-2 instead.

Regarding the reshuffling part - not at all. This is security by obscurity. It just make it a little bit more complicated, but it does not provide any additional security. BTW this branch is more applicable for such questions http://security.stackexchange.com/

P.S before blindly putting an -1, think about justifications. For my answer I have found at least one: - Is SHA1 better than md5 only because it generates a hash of 160 bits?

Answer 6

Why not just use SHA1 or SHA255?