diff --git a/metropolis/proto/api/management.proto b/metropolis/proto/api/management.proto
index 309fb19..9f0e646 100644
--- a/metropolis/proto/api/management.proto
+++ b/metropolis/proto/api/management.proto
@@ -44,4 +44,7 @@
     // cluster_directory contains information about individual nodes in the
     // cluster that can be used to dial the cluster's services.
     metropolis.proto.common.ClusterDirectory cluster_directory = 1;
+
+    // ca_public_key is the Ed25519 public key of the CA of the cluster.
+    bytes ca_public_key = 2;
 }