Security Philosophy for Machine-to-Machine (M2M) Authentication

In this guide, we discuss our philosophy behind implementing machine-to-machine (M2M) authentication using Descope’s client credentials flow or Descope Access Keys to securely exchange for JWTs.

This method is ideal for services that need to authenticate with each other without user interaction, providing a robust security framework for automated processes and microservices.

Overview

In the client credentials flow, Service A (the client) sends its client_id (Access Key ID) and client_secret (Access Key Secret) to Descope.

Descope validates the credentials and returns a JWT (access token), signed with Descope's private key. The JWT can include custom claims relevant to your service’s authorization logic.

Service A then passes the JWT to Service B (the downstream service), which uses it to authenticate Service A's request.

Key Security Benefits

One of the key security advantages of this approach is that the client_secret (Descope Access Key) is only stored and managed in one place—Service A. Here’s how it works:

• Secure Storage: Service A is responsible for securely storing the access key in a secure environment, such as a key management system or secret manager.
• Token Exchange: When Service A needs an access token, it exchanges the access key for a short-lived JWT, which it then sends to Service B.
• Key Rotation: By rotating the access key periodically, Service A minimizes the risk of secret leakage without needing to alter other parts of the infrastructure.
• JWT Transmission: Only the JWT is transmitted between services, reducing the exposure of long-lived secrets like the client_secret.

JWT Validation and Custom Claims

Service B only needs to validate the JWT it receives. The JWT includes:

• Cryptographic Signature: JWTs are signed by Descope and are tamper-evident. Service B can verify the signature without calling back to Service A or Descope.
• Custom Claims: The JWT can include specific claims such as permissions, roles, or identifiers, allowing Service B to perform fine-grained access control.

This architecture reduces the attack surface by centralizing secret management in Service A while maintaining distributed authorization using short-lived, verifiable tokens (JWTs).

By leveraging Descope's client credentials flow or access keys to exchange for JWTs, you can securely handle M2M authentication. This approach ensures centralized management of sensitive credentials, provides short-lived, tamper-proof tokens for authentication, and enables fine-grained access control between services.