Partial key autonomy

Proposal 1

Maintain the firmware and dev-key status quo while permitting everything else to be modified.

For each party P who so requests,

1. ask party P to generate
   • P_OS_key -- per Firmware security, guards the theft-deterrence code-path through the kernel and initramfs
   • P_FS_key -- see the bottom of OFW's loaddropins.fth; opens the NAND reflash lock.
   • P_LEASE_key -- per Firmware security, opens the activation lock
   • P_OATS_key -- per Theft deterrence protocol and Mass olpc-update, verifies theft-deterrence messages.
2. generate a firmware, initramfs, and olpc-update which contain the public values of these keys.
   • alternately, provide the keys through /ofw and rewrite the initramfs and olpc-update code to read /ofw
3. have OLPC return a signed version of the customized firmware to party P.

By installing the signed customized firmware on a stock machine, party P will be able to autonomously provide builds and activation leases and will be able to execute or modify the theft-deterrence protocol for that machine. Party P may also further delegate these abilities, e.g. with version-2 lease signatures. OLPC will retain responsibility for providing developer keys and firmware updates.

Benefits

This proposal preserves the status quo in three important ways:

• OLPC can generate developer keys itself
• Developer keys remain all-powerful for the laptops for which they are generated
• If v2 signature checking is implemented in the firmware, OLPC can delegate its ability to generate developer keys to others on a per-laptop basis

Risks

• it somewhat complicates the task of making, testing, distributing, and deploying releases.
• unless some care is taken, it poses a denial-of-service risk to innocent third-party users of locked machines.
  • (people willing to unlock their machines with a devkey or to maintain their own customized firmware suffer little additional risk.)