How should security teams replace static secrets in gateway-to-service authentication?

Why This Matters for Security Teams

Gateway-to-service authentication is often the quietest part of an architecture and one of the easiest places for secrets to spread. Hardcoded API keys, shared tokens, and embedded passwords are convenient until they are copied into CI logs, config files, support tickets, or replayed by an attacker. That is why NHI Management Group treats this as an identity problem, not just a vaulting problem, and why the State of Secrets in AppSec matters here: leaked credentials remain hard to remediate, and the operational cost is real.

Static secrets also create weak auditability. When the gateway uses the same credential for every request, teams cannot easily prove which workload called what, when, or under which context. Current guidance suggests replacing reusable secrets with cloud-native identity, signed assertions, and short-lived authorization decisions. That aligns with the broader direction in the OWASP Non-Human Identity Top 10 and with NHIMG research on Static vs Dynamic Secrets. In practice, many security teams discover the weakness only after a token has already been reused outside its intended path.

How It Works in Practice

The replacement pattern starts with workload identity. Instead of a gateway presenting a long-lived secret, the gateway proves what it is using cryptographic identity such as OIDC-issued workload tokens, SPIFFE/SPIRE identities, or platform-native service accounts. The service then evaluates that identity at request time and decides whether to allow the call based on context, not just a prebuilt role.

That changes the control plane in three practical ways:

• Issue temporary credentials per workload or per transaction, not shared secrets that live for months.

• Bind authentication to the calling workload, destination service, and request context so replay is less useful.

• Rotate or revoke access automatically when the task ends, the pod is replaced, or the route changes.

For gateway-to-service flows, the best pattern is usually signed requests plus short-lived tokens. The gateway authenticates to an identity provider, receives a scoped token, and forwards only the minimum proof needed for the target service to verify identity and authorisation. Where supported, mTLS strengthens the channel, but it should complement identity, not replace it. The key distinction is that the service should trust the request because it can verify the caller’s workload identity, not because it recognises a reusable secret.

NHIMG’s Guide to the Secret Sprawl Challenge shows why this matters operationally: duplicated secrets and scattered storage make cleanup slow and incomplete. In parallel, The 2025 State of NHIs and Secrets in Cybersecurity reports that 62% of secrets are duplicated across multiple locations, which is exactly the kind of sprawl that breaks gateway authentication hygiene. These controls tend to break down when the gateway must support legacy systems that only accept static API keys because the migration path is constrained by protocol compatibility, not policy intent.

Common Variations and Edge Cases

Tighter identity controls often increase integration effort, so teams have to balance security gains against legacy compatibility and delivery speed. The right answer is not always an immediate cutover; best practice is evolving toward phased replacement, especially where downstream services cannot yet validate signed identities or short-lived tokens.

One common exception is a third-party service that only accepts a fixed shared secret. In that case, security teams should isolate the secret behind the narrowest possible gateway boundary, store it in a managed secrets system, and plan a migration path to federation or token exchange. Another edge case is a multi-tenant gateway where a single credential would make tenant separation impossible to audit. In that environment, per-tenant identities and policy-as-code checks are more defensible than any shared credential model.

This is also where assume-breach thinking matters. If a gateway can call many services, a stolen static secret becomes a lateral-movement primitive. That risk is illustrated in NHIMG research on the 230M AWS environment compromise and the CI/CD pipeline exploitation case study, where exposed credentials turned one foothold into many. In environments with heavy batch traffic, the practical challenge is token churn and policy latency, so architecture teams should test whether short-lived credentials can scale before decommissioning the old secret path.

Related resources from NHI Mgmt Group

• How should security teams handle service access when static secrets keep leaking?
• How should security teams replace static secrets in Databricks pipelines?
• How should security teams replace static service account keys in cloud workloads?
• How should security teams replace client secrets in machine-to-machine authentication?