diff --git a/.dockerignore b/.dockerignore
index 351278b..d911b03 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -44,7 +44,9 @@
 **/[iI][dD]_[rR][sS][aA]
 **/[iI][dD]_[dD][sS][aA]
 **/[iI][dD]_[eE][cC][dD][sS][aA]
+**/[iI][dD]_[eE][cC][dD][sS][aA]_[sS][kK]
 **/[iI][dD]_[eE][dD]25519
+**/[iI][dD]_[eE][dD]25519_[sS][kK]
 
 # Dependencies: restored inside the image, never copied in.
 **/node_modules
diff --git a/.gitignore b/.gitignore
index 4c335ba..534d4e2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,4 +42,6 @@ node_modules/
 [iI][dD]_[rR][sS][aA]
 [iI][dD]_[dD][sS][aA]
 [iI][dD]_[eE][cC][dD][sS][aA]
+[iI][dD]_[eE][cC][dD][sS][aA]_[sS][kK]
 [iI][dD]_[eE][dD]25519
+[iI][dD]_[eE][dD]25519_[sS][kK]
diff --git a/TODO.md b/TODO.md
index 769cf3a..ad4785c 100644
--- a/TODO.md
+++ b/TODO.md
@@ -21,6 +21,10 @@ fmt-check, and commit.
 
 # Completed Steps
 
+- 2026-10-04: The canonical `.gitignore` and `.dockerignore` now also keep out
+  `id_ecdsa_sk` and `id_ed25519_sk`, the private key files `ssh-keygen` writes
+  for keys backed by a hardware security key (issue 81). Their `.pub` halves
+  stay trackable.
 - 2026-10-04: `package.json` now has `"license": "MIT"`, matching `LICENSE`, so
   yarn no longer prints "No license field" when `script/bootstrap` runs it
   inside the Docker phases (issue 76). That was the only yarn warning there.