Guillermo Rauch builds cpu-chat: sealed VMs talking through the CPU
A reproduction of OpenAI's findings on covert channels between machines with no internet.
Guillermo Rauch (@rauchg) shared cpu-chat on Monday, a reproduction of OpenAI's findings on covert communication through the CPU. The post drew about 1,030 likes.
In the post, Firecracker microVMs with no internet access exchanged messages using CPU contention, cache eviction timing and DRAM bandwidth. He says it worked across CPUs, on both x86 and an M5 chip.
Why it mattersIt shows that isolated sandboxes, often used to contain AI agents, can still leak information through shared hardware.
