Design Secure Webhook Transformation and Validation Pipeline

Create a robust webhook processing architecture that ensures maximum security, data integrity, and scalable event handling. Implement a solution that includes: 1) Cryptographic signature validation, 2) Event schema validation, 3) Idempotency tracking, 4) Retry mechanisms with exponential backoff, and 5) Comprehensive logging and audit trails. Provide a detailed design demonstrating how to handle various failure scenarios and ensure reliable event propagation.