Hardware Trust Anchors on a Modern System

Four places a system can "stand on solid ground." Hover any anchor for its capabilities and threat model.

Hardware Root of Trust Anchored in silicon, set at fabrication System Board Main CPU Package Application Cores OS & apps — large, untrusted surface TEE Region Intel SGX/TDX, AMD SEV, ARM TrustZone runs developer code in isolation ⚠ depends on microcode/firmware Secure Enclave Apple SEP, Titan M, Knox runs only signed firmware Discrete TPM Stores measurements & sealed keys TCG TPM 2.0 standard LPC / SPI bus External HSM (1U appliance) Enterprise key custody FIPS 140-3 Level 3+ tamper-responsive network / PCIe Color key: trusted region (silicon-isolated) depends on microcode / firmware packaging, buses & off-board hardware
The four anchors — stronger isolation toward the bottom, but harder to deploy
Trust anchorMain capabilityThreat model / what it assumes
TEE regionIsolates app code from the OS at runtime (SGX/TDX, SEV, TrustZone)Trusts CPU microcode & firmware; some side-channels break it
Secure EnclaveSeparate coprocessor running only signed firmware (SEP, Titan M, Knox)Protects keys even if the OS is fully compromised
Discrete TPMStores boot measurements & seals keys to system state (TPM 2.0)Off-CPU, so software can't extract keys; bus interposition is the risk
External HSMEnterprise key custody & bulk crypto, FIPS 140-3 L3+Tamper-responsive; keys never leave the appliance