Seagate ST9500421AS Princeton Attack on Software Encryption - Page 2

Princeton Attack on Software Encryption No probe points or external interfaces are provided to the key stored in disk drives. Moreover, any attempt to extract the tightly integrated memory from the drive package and move it to another system cuts off the power, locking the drive and erasing the encryption key from the drive's memory. Full Disk Encryption Q&A Note: Software encryption means that the encryption is implemented in software running on the computer. Hardware full disk encryption (FDE) means that the encryption is implemented in the processor hardware on the hard drive. Q: What types of encryption are vulnerable to the key theft highlighted in the Princeton paper? A: Most software encryption packages are vulnerable to this theft. In the vulnerable software encryption packages, the encryption key is kept in memory while the system is booted and running, allowing the operating system to encrypt data as it is written to disk. Since the key is preserved in memory during power on, it is possible to steal the key by locating that copy and saving it for use later. Software encryption programs can conceal the key by dismantling it and storing the pieces in various locations in memory, though this defense can degrade performance and explains why most software encryption programs keep the key intact in one location. Another way to defend against the freezing DRAM attack is to keep the encryption key in special CPU registers or a locked section of the CPU cache-a feature of few software encryption programs. Q: My key is 128 to 256 bits in 1 GB (or more) of memory. Isn't this like looking for a needle in a haystack? A: Usually the hacker must exploit some weakness in the operating system to access the system memory. By freezing the DRAM, the hacker can gain access to the system memory without having to circumvent the operating system or other protections designed to secure computer memory from unauthorized users. The process is as simple as freezing the DRAM, shutting down the computer, moving the DRAM to another computer and searching for encryption keys as described above. Once the program finds an encryption key, it copies the key elsewhere for later use. Locating the key is much easier because the operating system is not loaded and therefore unable to protect the computer's memory from nefarious searches. Q: Why would someone want to steal my key? Wouldn't it be easier to just steal my data? A: It depends on what the thief wants. In order for the frozen DRAM exploit to work, your computer must be up and running with software encryption working, so the thief could just steal your data by copying it from your computer to an external storage device, such as an external hard drive. The thief gets a copy of whatever you have on your computer at that time. By stealing the key, the thief can return at any time, power up your computer, install the encryption key and get your data. Q: Can I change my encryption key to keep a thief from getting my data? A: You must change your encryption key and rewrite all of the data that was encrypted under the previous encryption key. If someone has stolen your encryption key and you change to a new key, the data written under the previous key is vulnerable. In order to make the data secure, you must re-encrypt all of your data with the new encryption key. Q: If I power off my computer, am I vulnerable to data theft? A: No, provided you wait a few minutes after power down, until the memory loses its contents. If your data is encrypted and your system is powered off, your data is safe from theft. You must leave your computer in the hibernate mode or power it off completely to secure your data. In addition, it is important not to leave your computer unattended for a half hour or so (depending on the type of memory it uses), because data loaded to RAM does not disappear instantly.