Machine Identity Management: SPIFFE vs Vault vs Cloud IAM
Every organization needs to identify its services. But which approach is right? This guide compares the four most common machine identity strategies and explains when each excels.
SPIFFE/SPIRE
Best for: Cross-platform workload identity, multi-cloud, service mesh integration, Kubernetes-native identity.
- Automatic identity issuance via attestation
- Short-lived certificates with zero manual rotation
- Works across Kubernetes, VMs, bare metal, and cloud providers
- CNCF graduated standard — vendor-neutral
HashiCorp Vault PKI
Best for: Secret management combined with certificate issuance, organizations already using Vault.
- Strong secret storage and certificate management
- Rich policy system for secret access
- Requires Vault token distribution (creates its own secret management problem)
- Not a workload identity system — does not attest workloads
Kubernetes Service Accounts
Best for: Simple single-cluster Kubernetes deployments.
- Built into Kubernetes — no extra infrastructure
- Limited to one cluster — no federation
- Not cryptographic certificates — cannot be used for mTLS
- Tokens were long-lived before Kubernetes 1.24
Cloud IAM (AWS IAM, GCP Workload Identity)
Best for: Single-cloud deployments using cloud-native services.
- Deep integration with cloud provider services
- No infrastructure to manage
- Locked to one cloud provider — breaks in multi-cloud
- Not designed for service-to-service mTLS
Comparison Table
| Feature | SPIFFE/SPIRE | Vault PKI | K8s Service Accounts | Cloud IAM |
|---|---|---|---|---|
| Workload attestation | Yes | No | Limited | Cloud-specific |
| mTLS certificates | Yes (X.509-SVID) | Yes | No | No |
| Automatic rotation | Yes | Yes (with agent) | Partial (1.24+) | Yes |
| Multi-cloud | Yes | Yes | No | No |
| Federation | Yes (native) | Manual | No | Cross-account only |
| VM + Kubernetes | Yes | Yes | No | Partial |
| Open standard | CNCF (SPIFFE) | Proprietary | K8s-native | Proprietary |
The Right Choice Depends on Your Needs
Use SPIFFE/SPIRE when you need cross-platform, multi-cloud, or multi-cluster workload identity. Use Vault when secret management is the primary concern. Use K8s Service Accounts for simple single-cluster deployments. Use Cloud IAM for cloud-native services within a single provider.
For most organizations adopting zero trust, SPIFFE/SPIRE provides the most comprehensive and portable solution. Our free course teaches it from the ground up.