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dpop-adoption

Implement and debug OAuth 2.0 DPoP (RFC 9449) refresh token sender-constraining for WebCrypto, Node.js ES6, and browser runtimes integrating with Google's OAuth platform. Use when configuring non-extractable asymmetric key pairs (P-256), generating DPoP Proof JWTs for authorization code exchange and token refresh, or handling 400 use_dpop_nonce challenge retry loops at oauth2.googleapis.com/token. Don't use for unconstrained OAuth 2.0 flows (where refresh tokens are not bound to a client key pair), or for Google Cloud IAM / service account authentication.

skills/identity/dpop-adoption/SKILL.md

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Repository stars (not skill ratings): 23,462
Repository last updated: Nov 7, 2026
License: Apache-2.0

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# DPoP Adoption & Identity Security Architecture

Demonstrating Proof-of-Possession (DPoP, RFC 9449) secures OAuth 2.0 refresh
tokens against interception and replay attacks by cryptographically binding them
to a private key held exclusively by the client. In Google's OAuth 2.0 platform,
DPoP binds the refresh token at the token endpoint, while access tokens issued
for Google APIs are standard Bearer tokens (`token_type: "Bearer"`).

## 1. Core Cryptographic & Architectural Invariants

When implementing DPoP helpers or upgrading HTTP clients, you MUST adhere to the
following strict security invariants:

### A. Universal WebCrypto & Runtime Compatibility