Hardware-based keys are physical devices users carry to prove identity, while software-based keys use a phone or other virtual factor to perform the same function. Hardware is useful where mobile devices are restricted or impractical. Software reduces provisioning cost and can speed rollout, but both require strong governance and lifecycle management.
Why This Matters for Security Teams
Passwordless security keys are often treated as a simple replacement for passwords, but the real decision is about trust, recovery, and lifecycle control. Hardware-based keys give a physical possession factor with stronger resistance to phishing and endpoint compromise, while software-based keys trade some of that physical assurance for easier deployment and lower user friction. For identity teams, the difference matters most when access must survive lost devices, restricted endpoints, or regulated environments.
This is not just a user authentication detail. It affects how organisations enforce NIST Cybersecurity Framework 2.0 outcomes around access control, recovery, and resilience, especially when key issuance is tied to device posture or mobile app enrollment. NHI Management Group’s Ultimate Guide to NHIs is clear that identity security fails when lifecycle governance is weak, and the same pattern applies here: the factor is only as strong as enrollment, revocation, and recovery. In practice, many security teams discover weak key governance only after a lost device, locked-out executive, or support backlog has already exposed the gap.
How It Works in Practice
Hardware-based passwordless security keys are dedicated cryptographic devices, usually USB, NFC, or smart-card style, that store private keys in tamper-resistant hardware. They are well suited to high-assurance use cases because the secret never leaves the device, and the key can be paired with phishing-resistant protocols such as FIDO2 and WebAuthn. Software-based keys use a phone, desktop app, or platform credential to perform a similar function, often leveraging secure enclave or trusted platform features.
The practical difference is governance, not just form factor. Hardware keys usually require procurement, inventory, spares, and explicit recovery procedures. Software keys reduce distribution cost and can improve adoption, but they depend heavily on endpoint integrity, mobile device management, and account recovery controls. That means security teams should define:
- Which roles require hardware keys versus platform-based or software-based authentication.
- How enrollment is verified before a key is trusted.
- How lost, stolen, replaced, or retired devices are revoked.
- What fallback methods are allowed, and whether they weaken the passwordless design.
For operational guidance, CISA guidance on phishing-resistant MFA is a useful baseline, and the broader identity governance context in The State of Non-Human Identity Security shows why weak lifecycle controls are a recurring failure point. These controls tend to break down when organisations allow broad recovery exceptions, because attackers target the fallback path rather than the primary key.
Common Variations and Edge Cases
Tighter passwordless controls often increase support overhead, requiring organisations to balance phishing resistance against user recovery and device availability. That tradeoff is especially visible in hybrid workforces, BYOD environments, and regulated sectors where some users cannot carry a separate security key.
Current guidance suggests the strongest posture is not “hardware only” or “software only,” but a tiered model. Hardware keys are generally preferred for administrators, finance, and privileged access, while software-based keys can be acceptable for lower-risk users when paired with strong device management and real-time attestation. There is no universal standard for this yet, so policy should reflect business risk, not vendor convenience.
Edge cases matter. Shared kiosks, air-gapped systems, recovery after device loss, and workers without compatible phones can all force exceptions. Those exceptions should be time-bound and documented, not turned into permanent backdoors. The key question is whether the organisation can prove possession without creating an easy bypass. NHI Management Group’s research on identity governance gaps reinforces the same lesson: security degrades when recovery becomes more permissive than primary authentication.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST CSF 2.0, NIST SP 800-63, NIST Zero Trust (SP 800-207) and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST CSF 2.0 | PR.AC-1 | Directly relates to authentication and access control for passwordless keys. |
| NIST SP 800-63 | AAL2 | Assurance level guidance helps distinguish stronger hardware and software factors. |
| NIST Zero Trust (SP 800-207) | AC-6 | Least privilege matters when passwordless keys are used for privileged access. |
| OWASP Non-Human Identity Top 10 | NHI-02 | Lifecycle governance for non-human credentials maps well to passwordless key revocation. |
| NIST AI RMF | Risk management framing helps decide where software versus hardware keys are appropriate. |
Align passwordless enrollment and verification with PR.AC-1 and remove weak fallback methods.
Related resources from NHI Mgmt Group
- What is the difference between passkeys and hardware security keys in enterprise MFA?
- What is the difference between client secret authentication and certificate-based authentication for service principals?
- What is the difference between role-based access and API key governance for NHI security?
- What is the difference between SaaS supply chain security and software supply chain security?
