From 731668e87a50fbb876625bcf4baeea28bcabcc7f Mon Sep 17 00:00:00 2001
From: Robin Krahl <robin@nitrokey.com>
Date: Sun, 31 May 2026 14:58:45 +0200
Subject: [PATCH] Set initial signature counter to 1
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Returning the signature counter 0 would indicate that we don’t support
signature counters or that a counter error occured.
---
 CHANGELOG.md | 3 ++-
 src/state.rs | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ae12709..56eb092 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
--
+- Fix signature counter to improve spec compliance:
+  - Set the initial signature counter to 1.
 
 ## [v0.4.0-rc.1](https://github.com/trussed-dev/fido-authenticator/releases/tag/v0.4.0-rc.1) (2026-05-29)
 
diff --git a/src/state.rs b/src/state.rs
index 2de732b..a10a7ef 100644
--- a/src/state.rs
+++ b/src/state.rs
@@ -320,7 +320,9 @@ impl PersistentState {
             consecutive_pin_mismatches: 0,
             pin_hash: None,
             pin_code_point_length: 0,
-            timestamp: 0,
+            // Setting the signature counter to zero indicates that it is not supported or that a
+            // counter error occured, so we have to initialize it with a non-zero value.
+            timestamp: 1,
             min_pin_length: 0,
             min_pin_length_rp_ids: Vec::new(),
             force_pin_change: false,