2024-11-03 · Leo Aksoy
Webhook Signatures That Survive Partner Clock Skew
A narrow recipe for replay-resistant signatures when partners sit minutes away from NTP reality.
Clock skew shows up in Seoul just as often as anywhere else — CDNs, legacy ERP hooks, and aggressive VM snapshots all contribute. Rather than demanding perfect time sync, we model grace windows and nonce stores that tolerate skew without widening the attack surface arbitrarily.
During Integration Hardening Workshops we ask teams to pair canonical payload hashing with explicit drift monitors. When signatures begin failing at the edges of the window, alerts route to partnership engineering instead of mystery pages.
Finally, we publish the verification ladder for customer success: what partners can self-check before escalating. That reduces duplicate tickets and keeps engineering focused on systemic fixes.