Finally, a real standard for device security

Traditional ACME validates domain control using DNS or HTTP challenges to issue server certificates. ACME Device Attestation extends ACME with a new device-attest-01 challenge that validates hardware identity instead of domain ownership.

With ACME-DA, the device generates a key inside a TPM, Secure Enclave, or vTPM, and the secure element produces a signed attestation proving the hardware provenance of that key. The certificate authority verifies the attestation chain back to a known manufacturer root, and only then issues a hardware-bound client certificate. This allows the CA to know which physical device generated the keypair, enabling strong device identity at scale.

Legacy enrollment mechanisms such as SCEP, NDES, AD CS, and LDAP-based provisioning rely on passwords, shared secrets, device-supplied metadata, and user-controlled software claims. These signals can be stolen, spoofed, replayed, or reused from cloned systems, making device impersonation trivial once an attacker gains access to the enrollment material.

ACME Device Attestation provides guarantees that legacy methods cannot. It uses hardware-rooted attestation through TPM or Secure Enclave, enforces non-exportable private keys, and verifies manufacturer-signed platform certificates to prove device authenticity. Challenge binding prevents replay, and zero-touch provisioning removes the need for shared secrets. This eliminates entire attack classes involving device impersonation, stolen installers, and profile cloning.

Smallstep ACME Device Attestation supports attestation from TPM 2.0 using endorsement keys, attestation keys, and the platform certification chain, as well as from Apple Managed Device Attestation leveraging the Secure Enclave on supervised Apple devices.

It also supports Chrome Verified Access attestation and vTPM attestation for virtual machine fleets, including AWS NitroTPM, Azure vTPM, and GCP Shielded VMs. Each attestation chain is validated against the appropriate manufacturer trust bundle to ensure device authenticity.

Keys generated inside a TPM or Secure Enclave are non-exportable, protected by hardware isolation, usable only through approved signing or decryption operations, and attestable, meaning the hardware can prove where the keys were generated.

The certificate authority receives both the certificate signing request and the corresponding hardware attestation evidence, ensuring that the public key is backed by a genuine secure element rather than software alone.

Smallstep enforces multiple validation layers by validating attestation certificate chains back to manufacturer roots and gating issuance through inventory so that only known devices can obtain certificates. Attestation is cryptographically bound to the ACME order to prevent replay, and certificates are intentionally short-lived, requiring periodic re-attestation.

Revocation is continuous and tied to posture, inventory status, and compliance signals. Together, these controls ensure that Smallstep issues certificates only to provably authentic and authorized devices.

ACME Device Attestation is explicitly designed for cross-platform environments. Smallstep provides a cross-platform agent for Windows, macOS, and Linux, with support for physical TPMs, Secure Enclave, and vTPMs.

It also integrates with MDM platforms such as Intune, Jamf, and Workspace ONE, as well as ChromeOS Verified Access. The same attestation process works consistently across all supported device classes.

Both deployment models are supported. Smallstep can operate as a primary certificate authority, issuing hardware-attested device certificates directly, or as a registration authority that performs attestation verification before forwarding approved certificate signing requests to existing certificate authorities.

These backend CAs can include Microsoft AD CS or NDES, AWS Private CA, Google Cloud CAS, Vault PKI, or on-premises HSM-backed CAs. This approach allows organizations to add hardware-rooted enrollment to legacy PKI systems without rearchitecting them.

Zero-touch provisioning becomes secure because a device can prove its hardware identity at first boot and its attestation identifiers can be matched against preloaded inventory or MDM-fed entries. A certificate is then issued automatically without passwords or manual approval.

This enables true hands-free onboarding while improving security, unlike SCEP-based auto-enrollment approaches.

Certificates are intentionally short-lived, and devices must periodically re-attest using their secure element to renew them. Inventory status, posture signals, and policy are evaluated on every renewal to ensure the device remains authorized and compliant.

Revocation is triggered when a device is removed from inventory, when MDM or EDR posture checks fail, when the TPM or Secure Enclave state changes such as after a reset, or when an administrator explicitly revokes the device. Revocation blocks the issuance of new certificates, and short expiration ensures stale access naturally disappears.

ACME Device Attestation strengthens enforcement across multiple access layers. For Wi-Fi using EAP-TLS, RADIUS validates hardware-backed device certificates. For VPN access over IKEv2 or mTLS, gateways authenticate devices during tunnel establishment. In SSH environments, user certificates are issued only on attested devices, while internal APIs rely on mTLS identities rooted in hardware.

The same model extends to service meshes and workloads, where microservices or virtual machines present attested identities, and to SaaS and SSO platforms, where device identity becomes an evaluated login factor. ACME-DA provides a single, hardware-attested identity that spans all trust boundaries.

Yes, but with adjusted assurance levels. Smallstep distinguishes between corporate-owned devices, which use full hardware attestation, and BYOD devices, which rely on software-scoped, privacy-preserving identifiers.

ACME Device Attestation is primarily intended for managed fleets, while BYOD scenarios use non-attested enrollment profiles with optional access restrictions based on risk and policy.

Organizations should maintain an authoritative inventory source such as an MDM, API import, or OEM feed, and ensure network accessibility to ACME endpoints. Devices must have a TPM or Secure Enclave available to support hardware-based attestation.

They should also plan integrations for Wi-Fi, VPN, SSO, or workload access, and deploy Step CA Pro to enable high availability, HSM integration, auditing, and enterprise-scale operation.

Smallstep supports attestation for virtualized environments including AWS NitroTPM, Azure vTPM, Google Cloud Shielded VMs, and VMware vTPM.

vTPM attestation protects against virtual machine cloning and snapshot replay while enabling verification of instance metadata. This delivers cryptographically strong workload identity across hybrid and multi-cloud deployments.