HSM vs AWS Nitro Enclave
Another alternative secure execution environment is AWS Nitro Enclave, which provides isolation for workloads inside Amazon’s Nitro hypervisor architecture. Like Intel SGX, it represents a form of Trusted Execution Environment (TEE), but instead of being embedded in the CPU, it is implemented in the AWS cloud platform.
AWS Nitro Enclave
AWS Nitro Enclaves allow customers to launch a stripped-down virtual machine, often running a container, inside an isolated enclave. This enclave can run sensitive workloads without direct network access, reducing the risk of exposure. However, the enclave still runs on shared cloud infrastructure and inherits many of the complexities of the AWS ecosystem.
- TEE built on AWS Nitro hypervisor technology
- Enclaves typically run a Docker container image inside the isolated environment
- Still part of a shared hardware environment between trusted and untrusted zones
- Larger attack surface compared to a dedicated device, since code running in enclaves is customer-supplied and potentially complex
- Harder to review/audit, as enclave code may involve full Linux distributions or containers with large dependency trees
- Requires an HSM (CloudHSM or external device) for durable key storage and code signing
- Relies on AWS for the integrity of hypervisor isolation and enclave lifecycle management
Nitro Enclaves provide useful isolation for certain workloads, but as with SGX, they do not replace a dedicated cryptographic root of trust.
Hardware Security Module (HSM)
HSMs remain purpose-built, tamper-resistant devices designed specifically to protect keys and execute cryptographic operations.
- Dedicated hardware with bank-grade security
- Smaller attack surface (Vault), easier to review and audit compared to full Linux containers or hypervisors
- Integrated True Random Number Generator (TRNG) and FIPS-approved deterministic RNGs
- Tamper-resistant key storage with automatic zeroization on tamper events
- Strict access control exposed only through PKCS#11 interfaces
- Certified under FIPS 140-2/3 Level 3 and other international standards
- Hardware-enforced role separation and built-in MFA with USB tokens and PIN pads
Comparison Summary
| Aspect | AWS Nitro Enclave | HSM |
|---|---|---|
| Architecture | TEE inside AWS Nitro hypervisor | Dedicated cryptographic appliance |
| Workload | Customer-supplied container/VM | Minimal wallet code (Vault) only |
| Attack Surface | Large (Linux kernel, container stack, AWS hypervisor) | Minimal, firmware + cryptographic APIs |
| Key Storage | Not native; requires HSM integration | Native tamper-resistant storage |
| Randomness | Depends on host entropy | Hardware TRNG + FIPS-approved DRBG |
| Auditability | Complex; full container OS and code | Narrow codebase, easier to audit |
| Certification | No FIPS 140-3 equivalent | FIPS 140-3, PCI HSM, Common Criteria |
| Role Separation | Software-enforced IAM policies | Hardware-enforced with MFA tokens |
| Use in Custody | Needs HSM for secure keys | Can act as the root of trust |
AWS Nitro Enclaves provide useful isolation mechanisms within cloud infrastructure, especially for reducing the attack surface of sensitive workloads. However, they rely on complex hypervisors and container environments, making them harder to audit and less predictable than dedicated hardware. Just like SGX, Nitro Enclaves still require HSMs for secure key storage, code signing, and cryptographic assurance. For custody systems that demand bank-grade security and independently certifiable trust anchors, HSMs remain the superior foundation.