1. TPM, UEFI, Trusted Boot, Secure Boot

2. How Does a PC Boot? First: History
Code entered on Hand Switches
Non-Volatile Memory; infrequent cold boot
Development of ROM-based IPL
PC developed multi-stage boot process

3. Power Up Sequence POST – Power On Self Test First code that runs
First code that runs
Part of the BIOS
Checks hardware to prevent boot failure
Runs BIOS/POST code in other devices
BIOS must know how to operate devices
Each BIOS crafted for each motherboard

4. Initial Program Load - IPL
Original PC booted each device in fixed order
Floppy, CD, HDD, Net
Newer BIOS now can change boot order
Loads boot code from device
Secondary boot loader
Stored in particular track of FDD/HDD
Independent of software architecture

5. Boot Loader Knows about device architecture
HDD – Partition tables, block size,
File Structure: FAT16, FAT32, NTFS etc
Finds the OS boot program
MS Boot loader
From a particular named file
Linux loader

6. OS Loader What you see when the Operating System Starts
Launches and configures the OS for the hardware
Installs relevant device drivers
Checks license and file system
Gets network operating etc

7. Security BIOS is in Flash – can be changed
User code can write to flash memory
Attacker can control machine from 1st power
HDD Boot sector can be changed
(boot sector virus)
OS Loader can be changed

8. TPM and BIOS BIOS is in control from POST
BIOS asks TPM for verification
BIOS can still be attacked
OS/CPU must protect BIOS
BIOS chip could still be changed
BIOS asks TPM to verify Boot Loader
BIOS could still boot something if verify failed
Hardware still usable if BIOS permits

9. Secure Boot BIOS will only boot authenticated boot loader
Boot loader only boots authentic OS
BitLocker must be enabled to secure disk
BIOS cannot then override TPM signing
BIOS could still boot another device unless locked
BIOS could be replaced to use another disc
Original disc still cryptographically secured

10. TPM Weakness Should be tamperproof Used in Games Console
Gamers motivated to break-in
Hardware attack details publish
Split chip open and collect key from Bus
Use brute force decryption for game keys
Manufacture problem not design problem?

11. UEFI Duplication between BIOS and OS
Both need device drivers
BIOS – TPM secure boot is optional
UEFI addresses this
UEFI is part of BIOS
Performs Boot Loader function
Checks OS signature without TPM
Will refuse to boot
Knows file structure
Drivers come from OS disk

12. Features Larger disks / Newer Hardware Eliminates boot virus attacks
Secures OS
Gives manufactures' control of hardware use
Can still work with BitLocker/TPM
Still vulnerable
Contains buffer overflow error (Samsung)
BIOS reflashable/rechipable

13. Unified Extensible Firmware Interface

14. Fully Trustworthy? Anti-Evil Maid method
Store signatures of BIOS etc in TPM
User checks TPM signature using:
Password
Physical device (USB stick with crypto key)
All signatures checked
Detects any non-authentic code
BitLocker not needed
Detects compromise on any component