API Encryption: TLS 1.3, mTLS, BYOK & Best Practices | Qodex.ai

The weaknesses in API attract attackers to capture the company’s critical resources. The security challenges occurred from improper security features, authentication, and access control. Knowing the security challenges helps the developer quickly identify and secure the API from internal and external threats.

APIs are frequent targets for cyberattacks because they act as gateways to valuable and sensitive data—including financial information, business-critical records, and personal user details. As APIs connect different software applications and services, they become attractive to attackers seeking opportunities for data theft, fraud, or service disruption. The prevalence of APIs in modern digital infrastructures only increases their exposure, especially since many are publicly accessible over the internet.

Common vulnerabilities that put APIs at risk include inadequate authentication, insufficient input validation, and flawed business logic. When these security gaps exist, it becomes easier for attackers to exploit APIs for unauthorized access or to cause operational and reputational damage to the business. By understanding these risks and addressing them proactively, developers can better safeguard their APIs and the sensitive data they handle.

Mutual TLS (mTLS): When & Where to Use It

Use mTLS for service-to-service and zero-trust scenarios where both sides must prove identity. mTLS pairs transport encryption with client certificate authentication, eliminating bearer tokens on internal mesh links and reducing token theft risk. OWASP’s TLS guidance highlights certificate handling, strong defaults, and revocation considerations—use it as your baseline playbook.

Perfect Forward Secrecy & Cipher Suite Choices

Choose ephemeral ECDHE key exchange for perfect forward secrecy (PFS) so a leaked long-term key cannot decrypt past traffic. Pair with AEAD ciphers (e.g., AES-GCM or ChaCha20-Poly1305) to combine confidentiality and integrity. Align with NIST/OWASP guidance when pruning legacy suites and testing compatibility.

Key Management 101: BYOK, KMS/HSM & Rotation

Strong crypto fails without strong key management. Use KMS/HSM for key generation, storage, and access control; adopt envelope encryption (KEK in KMS → DEK per resource) and automated rotation tied to TTLs and incident playbooks. If you need tighter control for compliance, implement BYOK so your keys never leave your trust boundary while still integrating with the platform’s control plane. Postman’s BYOK announcement is a good model for operationalizing this pattern.

JWS vs. JWE: Don’t Confuse Signing with Encryption

JWS (signed JWT) proves integrity and authenticity—but the payload can still be read by anyone holding the token. JWE (encrypted JWT) protects confidentiality. Use JWS for access tokens and JWE (or field-level encryption) when the token itself carries sensitive data. Combine with short TTLs, rotation, and audience scoping.

TLS Hardening Mini-Playbook

• Prefer TLS 1.3, enable OCSP stapling, HSTS, disable TLS 1.0/1.1 and weak ciphers.

• Use ECDSA certs where possible for performance and smaller handshakes; keep RSA 2048+ only for backward compatibility.

• Automate cert issuance/renewal (ACME) and run pre-deploy TLS smoke tests in CI (e.g., tls-scan).

• Pin by SPKI only when you control issuance and can rotate safely; otherwise, rely on CT + monitoring.
  This aligns with NIST’s TLS 1.3 push and OWASP TLS guidance.

Logging & Monitoring Without Leaking Secrets

Collect detailed API request logs for detection and forensics—but never log secrets, raw access tokens, private keys, or unredacted PII. Mask sensitive fields, sign logs for integrity, and alert on key misuse (e.g., spikes from unusual IPs). DreamFactory’s guidance on API request logging covers why this matters for security and compliance and how to do it safely.

Field-Level & Format-Preserving Encryption

When only parts of the payload are sensitive (e.g., SSNs, PANs), use field-level encryption or tokenization so downstream services operate on de-identified data. Consider format-preserving encryption where schemas or validators require exact shapes. Keep keys scoped per field/class of data to limit blast radius.

API Gateway Policies for Crypto

Terminate TLS at the gateway/ingress, enforce mTLS for internal hops, and propagate identity via short-lived, audience-scoped tokens. Add gateway policies for header normalization, strict transport security, and replay prevention (nonce + timestamp validation). This centralizes crypto posture and simplifies audits.

CI/CD: Crypto Controls You Can Ship Today

• Pre-commit: secret scanning (keys, tokens).

• Build: SAST rules for weak crypto (no SHA-1/MD5; ban static IVs).

• Pre-prod: TLS test job against preview env (versions, ciphers, OCSP).

• Post-deploy: key rotation job + smoke tests, alerts on cert expiry, anomaly detection on KMS logs.
  These controls keep encryption from drifting as you scale.

Compliance Map: OWASP & NIST

Map your controls to OWASP ASVS V9 (Data Protection) and V10 (Communications Security), then align TLS settings with NIST SP 800-52r2. This gives product, security, and compliance teams a shared checklist and clear acceptance criteria for crypto readiness.

Some of the Security challenges commonly found in the API are as follows:

1. Broken Object Level Authorization

• Broken object-level authorization is a common API security challenge that occurs when the mechanism controlling access to resources or objects within an API is flawed or improperly implemented. This vulnerability allows unauthorized users to gain access to sensitive information or manipulate resources they shouldn’t have access to.

•  Prevention – To mitigate this challenge, developers must define and enforce proper access controls based on user privileges, roles, and the sensitivity of the resources.
  
  

2. Broken User Authentication

• Broken user authentication is an API security challenge that arises when authentication mechanisms are weak or improperly implemented. This vulnerability enables malicious actors to gain unauthorized access to user accounts or sensitive information.

• Prevention – To address this challenge, developers should enforce strong password policies, implement secure password reset functionality, and employ multi-factor authentication where possible.
  
  

3. Redundant Exposure of Data

• Redundant exposure of data is a significant API security challenge that occurs when APIs provide access to more data than necessary, potentially exposing sensitive or confidential information to unauthorized users.

• Prevention – To mitigate this challenge, developers should adopt the principle of least privilege, ensuring that APIs expose only the minimum required information. Data anonymization and pseudonymization techniques can also enhance data privacy and minimize the risk of exposing personally identifiable information.
  
  

4. Inadequate Resources and Request Management

• The attacker sends the request to the API than the specified limit. As a result, it leads to denial of service or interruption of its function.

• Prevention – The developer can avoid it by limiting the number of resource allocations and the number of requests processed by the API at the given time. Then, it will notify the application to process requests within the specified limit.
  
  

5. Disrupted Function Level Authorization

• Authorization acts as a gateway to the critical resources of the organization. The issues in the authorization mechanism enable access to the sensitive resources of the organization. The attacker sending requests to such resources will gain access and steal the data.

• Prevention – It is avoided by applying multi-factor authentication to allow authorized users access to sensitive resources.
  
  

6. Mass Assignment

• Mass Assignment speeds the request process by delivering the input request by automatically assigning the object properties. However, the attacker can alter the object properties to access the organization’s critical resources. It is rectified by manually setting the object identifier and using tools to monitor the abnormal functions of the API.

• Prevention – To prevent mass assignment vulnerabilities, validate and sanitize user input thoroughly, implement strict input filtering, and utilize a whitelist approach for accepting only trusted and expected properties during object assignment.
  
  

7. Security Misconfigurations in API

API misconfiguration refers to weaknesses found in the server favourable for cyber-attackers. It acts as a gateway for cyber threats to enter the organization and disrupt the entire functionalities.

It occurs at any level of the organization, from the system level to the application level. The flaws in the systems, access, and data lead to the compromise of API. It leads to severe data breaches and the stealing of sensitive organizational resources.

Some common misconfiguration that occurs in the Application Programming Interface that question the security of the organization include

Insecure Data Storage and Data Transmission

The organization’s sensitive data, including confidential files, customer details, account details, are not properly encrypted and stored in the databases. As a result, it leads to data breaches that cause severe effects on the organization. In addition, the leakage of critical data brings down its reputation to affect its growth and customer satisfaction.

Passwords

Passwords play a critical role in the security process. It acts as a key to access all sorts of accounts. The passwords are appropriately secured to avoid unauthorized access to essential resources. However, using the same password across all the web applications opens a threat to the organization. Therefore, a proper encryption technique must be followed while sending from one user to another. In addition, the passwords should be encrypted before storing them in any file location.

The security misconfiguration causes severe damage to the organization. The early detection of the misconfiguration helps the organization strengthen its ability to protect from cyber threats. The automated process should be employed to detect the security misconfigurations in API and resolve it.