27 Jun 2025

The Leaders Are Already Securing APIs with FAPI + mTLS

API Security

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1. Financial-Grade APIs: The new de facto standard

Forget outdated client secrets. In Open Banking, Financial-grade API (FAPI) has become the gold standard for API security and compliance. The OpenID Foundation calls FAPI “a high-security API protection profile” already “adopted as a nationwide standard in many countries.” FAPI builds on OAuth 2.0/OpenID Connect with extra cryptography: mandatory mTLS for client authentication, PKI-based client identity, and certificate-bound (“sender-constrained”) access tokens. This framework addresses critical gaps in API access security and dramatically reduces common API security vulnerabilities. With regulatory bodies and industry leaders converging on this model, it’s clear that FAPI isn’t just for banks - it’s a blueprint for any sector managing sensitive data over APIs. Whether you're in finance, healthcare, telecom, or tech, applying a FAPI-style approach can strengthen your security posture and future-proof your architecture.

→ Download Now: API Security Report: Helping Enterprises Recognize and Address Critical Risks

2. Payment giants demand mTLS

The card networks aren’t waiting for regulators. Mastercard and Visa already mandate mTLS on their APIs. Mastercard’s Track payment service announced mandatory two-way TLS on webhook notifications, and Visa’s platform requires mutual TLS for backend integrations. These powerful, non-regulated industry leaders are sending a clear signal: “No certificate, no connection.” This model ensures identity verification using strong cryptography, helping to enhance API security while deterring impersonation attacks. Their actions demonstrate that mTLS is more than a recommendation; it's a necessity for modern API cybersecurity. Any business transmitting payment or personal data via APIs should recognize this trend and prioritize mutual TLS as a baseline control.

3. The API key trap: Stop waiting for disaster

Still relying on static API keys or bearer tokens? It’s a ticking time bomb. Keys are static secrets that leak everywhere - from public GitHub repos to cloud configs - yet too many organizations treat them as bulletproof. The reality: any leaked key is a direct invitation for attackers. In January 2025, U.S. Treasury hackers “gained unauthorized access to a stolen… API key,” then roamed networks unchecked. That’s a classic API security vulnerabilities example: one key opened the vault. Perimeter firewalls can't detect a compromised key. Attackers increasingly scan for exposed API keys, knowing they offer a silent pathway past traditional defences. This incident should be a wake-up call for organizations to rethink their approach to API Security. Basic, symmetric keys are not enough - you need asymmetric, certificate-backed, short-lived credentials that bind tokens to identities. This level of control enables hardening keystores and prevents token replay.

4. Crypto-based API protection: No excuses

Here’s your call to action: if your APIs touch money, health data, or partner systems, move beyond symmetric, static keys now. Protect every API call with cryptographic controls – think mutual TLS, X.509 client certificates, and certificate-bound tokens. In practice, it means binding tokens to client certificates and enforcing mTLS on each request to prevent misuse or replay. APIs must be treated as privileged interfaces - not public entry points secured by static strings. Advanced methods like OAuth private_key_jwt and DPoP (Demonstration of Proof-of-Possession) provide scalable paths toward signature-based trust. These models offer provable identity and context, which form the foundation of future-ready API protection solutions.

Raidiam Connect is built for exactly this leap. It’s an enterprise-grade API access management solution that delivers FAPI-style security out of the box – rapid mTLS onboarding, certificate-bound OAuth tokens, and strong PKI client identity. Why reinvent the wheel? Leaders are already securing data with FAPI and mTLS – Raidiam Connect makes it easy to follow their lead with proven, standards-based approaches to API access security.

📥 Download the API Security Report to gain exclusive insights from Raidiam’s API security profiling study. Inside, you'll discover:

Real-world API security vulnerabilities from recent breaches
Analysis of current enterprise security postures—including where most organizations fall short
Practical recommendations for API access security

Whether you're in security architecture, compliance, DevOps, or IT leadership, this report will help you evaluate your current API security approach and chart a practical path forward.

Don't wait until a breach exposes the gaps. Arm your team with expert data, proven frameworks, and next-step strategies that can close your API security gap today.

📄 Get the full report here and take the first step toward securing your machine-to-machine infrastructure for 2025 and beyond.

Sources: The above trends are confirmed by industry standards and news. For example, the OpenID Foundation notes that FAPI “has been adopted as a nationwide standard in many countries”, and official docs show Mastercard and Visa enforcing mTLS. Likewise, recent breaches demonstrate the dangers of static keys. Raidiam Connect builds on these proven standards.