Crypto, hashes and password questions, total noob?

Question

I've read several stackoverflow posts about this topic, particularly this one:

Secure hash and salt for PHP passwords

but I still have a few questions, I need some clarification, please let me know if the following statements are true and explain your comments:

1. If someone has access to your database/data, then they would still have to figure out your hashing algorithm and your data would still be somewhat secure, depending on your algorithm? All they would have is the hash and the salt.

2. If someone has access to your database/data and your source code, then it seems like no matter what your do, your hashing algorithm can be reversed engineered, the only thing you would have on your side would be how complex and time consuming your algorithm is?

3. It seems like the weakest link is: how secure your own systems are and who has access to it?

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Lasse V. Karlsen ... brings up a good point, if your data is compromised then game over ... my follow up question is: what types of attacks are these hashes trying to protect against? I've read about rainbow table and dictionary attacks (brute force), but how are these attacks administered?

Answer 1

When hashing a password, it is one way. So it is very difficult to get the password even if you have the salt, source and alot of cpu cyles to burn.

Answer 2

If someone has access to your database/data, then they would still have to figure out your hashing algorithm and your data would still be somewhat secure, depending on your algorithm? All they would have is the hash and the salt.

This might be all a really dedicated opponent would need. Much of this answer depends on how valuable the data is, which would tell you how motivated the opponent is. Credit card numbers are going to be extremely valuable, and criminal attackers seem to have plenty of time and accomplices to do their dirty work. Some bad guys have been known to farm out key decryption tasks to botnets!

If someone has access to your database/data and your source code, then it seems like no matter what your do, your hashing algorithm can be reversed engineered, the only thing you would have on your side would be how complex and time consuming your algorithm is?

If they have access to your source and all the data, the question is going to be "how did you load your key into the memory of the server in the first place?" If it's embedded in the data or in the program code, it's game over and you've lost. If it was hand-keyed by an operator at the machine's boot time, it should be as secure as your trust in your operator. If it is stored in an HSM*, it should still be secure.

And if they have root-level authority access to your running machine, then they can probably trigger and recover a memory dump that will reveal the secret key.

It seems like the weakest link is: how secure your own systems are and who has access to it?

This is true. But there are alternatives that help improve security.

For bank-like protection, the kind that passes security and industry audits, it's recommended that you use a *Hardware Security Module (HSM) to perform key storage and encryption/decryption functions. The commercial strength HSMs we're looking at cost 10s of thousands of dollars or more each, depending on capacity. But I have seen hardware encryption cards that plug into a PCI slot that cost substantially less.

The idea behind an HSM is that the encryption happens on a secure, hardened platform that nobody has access to without the secret keys. Most of them have cabinets with intrusion detection switches, trip wires, epoxied chips, and memory that will self-destruct if tampered with. Not even the legitimate owner or the factory should be able to recover the database key from an HSM without the set of authorized crypto keys (usually carried on smart cards.)

For a very small installation, an HSM can be as simple as a smart card. Smart cards aren't high performance encryption devices, though, so you can't pump more than about one decryption transaction per second through them. Systems using smart cards usually just store the root key, then decrypt the working database key on the smart card and send it back to the database accessing system. These will still yield the working database key if the attacker can access running memory, or if the attacker can sniff the USB traffic to and from the smart card.

And I have no experience getting TPM chips to work (yet), but theoretically they can be used to securely store keys on a machine. Again, it is still no defense against an attacker taking a memory dump while the key is loaded in memory, but they would prevent a stolen hard drive containing code and data from revealing its secrets.

Answer 3

( OP )

brings up a good point, if your data is compromised then game over ... my follow up question is: what types of attacks are these hashes trying to protect against? I've read about rainbow table and dictionary attacks (brute force), but how are these attacks administered

( discussion )

It's not a game, except to the attacker. Research these terms:

• Sarbanes-Oxley
• Gramm-Leach-Bliley Act (GLBA)
• HIPAA
• Digital Millenium Copyright Act (DMCA)
• PATRIOT Act

Then tell us ( as thought provocation for you ) how do we protect against whom? For one thing, it is the efforts of innocents vis-a-vis intruders - and for another it is data-recovery if part of the system fails.

It is an interesting experiment that the original intent of tcp/ip and so on is advertised as being a weapon of war, survivability under attacks. Okay, so passwords are hashed - no one can recover them ...

Which, duh, includes the owner-operator of the system.

So you build a robust record locking tool that implements key controls, then political pressures force the use of brand-x tools.

You can read Federal Information Security Management Act (FISMA) and by the time you have read it some governmental entity somewhere will have had an entire disk either stolen or compromised.

How would you protect that disk if it was your personal identity information on that disk.

I can tell you from the caliber of Martin Liversage and jadeters they will be paying attention.