Client: send join request with signed message to verify validity
diff --git a/core/client/go.mod b/core/client/go.mod
index 4f10753..1460cca 100644
--- a/core/client/go.mod
+++ b/core/client/go.mod
@@ -7,5 +7,6 @@
 	gioui.org/cmd v0.0.0-20211214104907-f5c9d2725c7b
 	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e
 	github.com/slackhq/nebula v1.5.1
+	golang.org/x/crypto v0.0.0-20211202192323-5770296d904e
 	golang.org/x/tools v0.1.8-0.20211022200916-316ba0b74098 // indirect
 )