1. Presented by Kartik Patel
Cold Boot Attack
Presented by Kartik Patel

2. Information storage
Information is stored in the Dynamic Random Access Memory (DRAM) on a computer
DRAM contains programs that are required for a computer to function
Each bit of data is stored on a separate capacitor (like a big bucket)
Capacitor needs to be refreshed every few milliseconds as it stores 1’s and 0’s
Example:
Logging into your computer stores the
password in DRAM
access to all user files
Why DRAM needs to be refreshed:
memory cells leak away, so without being refreshed the stored data would eventually be lost.
Bits are stored in the capacitator with 1’s, goes to ground state after when they discharge
Capacitor

3. Cold boot attack Performed on Dynamic Random Access Memory (DRAM)
Known as volatile memory space
People been taught that all their data will be erased when power is removed
Misconception, data remains there for a few seconds
Typically data is lost gradually over a period of seconds
Decaying stage begins when a computer has lost its power
This is memory which available at runtime, when you have running applications open it get stored in the DRAM
When you close the program it is removed from there which becomes available for other applications

4. How.. Keys have seconds to minutes before bits start to decay
Keys left for too long when trying to extract, it can cause corruption
This image decayed within 2 mins

5. How are attack performed
Access is required to the physical machine
Matter of seconds to extract all the data
Non – Destructive attack
Copied to a external drive
They pose a particular threat to laptop users who rely on disk encryption products, since an adversary who steals a laptop while an encrypted disk it can employ our attacks to access the contents, even if the computer is screen-locked or suspended.
Copy is made to a eternal device due to stake frame. Don’t want to overwrite original bits in RAM causing the entire data becoming corrupt

6. Cooling the DRAM
Change in temperatures have different effects on the number of bit decaying
Cooling the DRAM decreases the number of bits decaying
Use inverted can of caned air
Below -50 degrees, found fewer than 1% of bits decayed
Use liquid nitrogen after canned air
Cooling to even lower temperature, found -196 found even less bits decayed

7. Comparison

8. Exploiting DRAM Remanence
Reboot the machine and launch the custom kernel
Cut the power to the machine, then restores the power and boots a custom kernel via USB/external device
This prevents the OS of any opportunity to scrub memory before shutting down
Cuts the power and transplants the DRAM modules to an attacker’s machine
This prevents the original BIOS and PC hardware of any chance to clear the memory
The most advanced, cool the memory chip, take it out, put it into the attackers computer and then the file dumping will begin

9. Example.. Windows Vista – BitLocker
Windows Vista used a full disk encryption mechanism which is known to be BitLocker. This is designed to protect user data stored on the disk by providing encryption for the entire volume.
User logs in and then puts the computer in lock mode
Password to the computer is stored in DRAM
Attacker had access to the physical device and attach external device with attack software
Power computer down, remove the battery, add the battery and power on
Booted by external device, data starts to be dumped to external device including login key
Now all the keys will decrypt the computers hard disk and access to all files
On this computer the DRAM didn't’t need to be cooled because it had the old circuit boards put in.

10. Reconstruction of keys
Experiment showed that keys normally go to ground state
Very few bits go the opposite way
Speed reconstruction was used to re-create keys to its original state which Is more efficient
Can correct errors more efficiently with lower bit rate, can correct even if there is high bit error
From 5% to 50%
When the bits were decaying, a experiment showed that it goes to a ground state. There are a few bits which go to opposite way, but it is assumed to be 0 when reconstructing keys
Bits have also been predicted in the order that they start to decay, this was learned over a series of time trials

11. Reconstructing / Identifying key
Data Encryption Standard (DES) keys
Advanced Encryption Standard (AES) keys
Tweak keys
RSA private keys
Identifying keys in memory
Identifying AES keys
Identifying RSA keys

12. Mitigate Techniques
Best counter measure is suggested to discard or obscuring encryption keys before and adversary gains physical access.
Prevents memory dumping software from been executed
Make contents of the memory decay more readily
Adding passwords to boot from external device
Difficult to defend against because cryptographic keys are in active use and need to be stored somewhere

13. Mitigation methods Scrubbing memory Suspending a system safely
Software which overwrite keys in memory which is no longer needed
Runtime libraries and OS should clear memory more proactively
Systems can clear memory on boot time before loading OS
Suspending a system safely
Users can protect themselves by completely powering down the computer and waiting for a moment for all keys to be removed.

14. Methods [cont.] Avoidance of pre-computation encryption keys
Key expansion
Physically protecting the memory
Locked and encase DRAM in material which frustrates on the attempt of removal
Architectural changes
Making them lose their state quickly
Key-store hardware that erases its state on power-up, reset and shutdown
Will work long as encryption keys are destroyed on reset or power loss
Architectural changes - Not good now but maybe in the future

15. Summary What is cool boot attack and how they are performed
Ways that data bits keys can last longer in DRAM
Exploiting DRAM remenance and key methods for reconstruction
Ways that cool boot attack can be mitigated

16. Criticisms There still is no proper defenses against cold boot
Scrubbing memory still doesn't protect against important keys which are required to be kept in memory
Attacker can swap out the hard drive, bypass the sanity check of password and boot the computer
Users wait for their computer to power down then reboot it, rather then machine in sleep mode (trade off security vs usability)

17. Questions?