Hardware Roots of Trust — TPM, HSM, Secure Boot

Manish Garg
Manish Garg Associate of (ISC)² · RingSafe
Apr 26, 2026
5 min read
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Last updated: April 29, 2026

TPM 2.0, HSM, ARM TrustZone, SGX/SEV, secure-element chips — what HRoT primitives offer, measured boot, key storage, attestation, confidential computing for cloud workloads.

A Bengaluru hardware startup shipped 50,000 IoT smart-meters to a state utility. Six months later, security researchers extracted the firmware-signing key from one device and demonstrated they could push malicious firmware updates to all 50,000. The recall cost was ₹18 crore; the regulatory fallout was worse. The root cause: the signing key sat in regular flash with no hardware protection. This module covers hardware roots of trust — the chip-level primitives that make device security tractable.

What a hardware root of trust is

A hardware root of trust (HRoT) is a tamper-resistant chip or chip-region that holds cryptographic secrets the rest of the system cannot extract. Software running on the main CPU can ask the HRoT to sign, decrypt, or verify — but never sees the underlying key. The HRoT is the anchor; everything else (boot, attestation, key storage) chains up to it.

The common forms:

  • TPM 2.0 — discrete chip on the motherboard, used by Windows/Linux for BitLocker/LUKS, measured boot, attestation
  • Apple Secure Enclave — separate processor on iPhone/Mac SoC; holds biometric and keychain keys
  • ARM TrustZone — secure-world / normal-world split on ARM SoCs; basis for Android Keystore
  • Intel SGX / TDX, AMD SEV-SNP — confidential-computing primitives in server CPUs
  • HSM (Hardware Security Module) — network-attached or PCIe; FIPS 140-2/3 certified for high-value keys
  • Microcontroller secure-element (Microchip ATECC, NXP A71CH) — small chips for IoT
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