Securing an appliance

Question

Scenario:

We are in the position to offer a local appliance to run a version of our proprietary software, which is normally provided as SaaS.

Question:

What steps can be taken to mitigate trivial reverse-engineering in an untrusted environment, where they will have physical access to the box?

Clearly, it's 100% impossible to fully prevent IP leaks, as physical access is total access.

That said, what technical techniques could be applied to make reverse-engineering difficult/unfeasible?

Edit, for details:

• The project is international, so legally limited
• Network access is available, so perhaps a plan could be: Store applications on an encrypted filesystem, require a connection to one of our servers to retrieve the key for decryption, or something like that - anyone have any experience / insight?

Answer 1

Hardware security tokens as mentioned can provide some security against piracy.

Not knowing what your software is, or what it does, it's hard to know what solutions could work. Are you putting the box on-site because it is more efficient? Are you putting the box on site so that the customer can administer it themselves? Is it because the customer is running it on an isolated network?

Many enterprise grade solutions use strict license agreements and cryptographicaly secure software keys with the name of the purchasing enterprise and the date of expiry clearly in them. It means that even employees who steal code only have limited use of it as the origin and time limits on its usage are clear.

But all this does little to nothing to protect against reverse-engineering.

Code obfuscators and obfuscating compilers might help you a bit. Again, it depends on your application, your application team, etc.

Physical tamper-resistance might also help, but it limits your ability to support the physical hardware. The payment card industry uses wire mesh inside some of their hardware with keys stored in volatile memory so that if the case is tampered with, important decryption keys are lost, rendering the device useless. Similar techniques are applied to HSMs (Hardware Security Modules), which are effectively tamper-resistant vaults for storing important crypto-keys.

The whole game is risk management. The expense of launching a lawsuit, the damage caused by a leak, the cost of securing the code, it all has to be weighed. Few secrets are so important that they need to be protected at all costs. The delay to market may cost you your time advantage, allowing a competitor to reach a comparable solution at a better price before you can get your locked down version out the door.

Answer 2

You can use obfuscation which can become cumbersome/complex, and if undocumented, not a good idea, or you can use something like Sentinel HASP. In a business situation though, SLA, TOS and voiding warranties make strong impacts when spelled out clearly. "THOU SHALL NOT ACCESS/REVERSE ENGINEER/etc, etc." It won't stop the reversing, but businesses take financial loss serious. More options would be boot encryption, passwords via booting, etc., however those too can become a management headache

EDITED TO ADD A LINK

http://palpapers.plynt.com/issues/2008Jul/defend-reverse-engineering/