sim: add EC256 encryption key

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/enc-ec256-priv.pem b/enc-ec256-priv.pem
new file mode 100644
index 0000000..352615a
--- /dev/null
+++ b/enc-ec256-priv.pem
@@ -0,0 +1,5 @@
+-----BEGIN PRIVATE KEY-----
+MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg9h5Rnfj63aG32alk
+ZDtU0D3QH+V42ReYpSjKzGtnngahRANCAASKRHMAlMmAJzENIzZr6Wmfy8V8yEQa
+k+bufYamrl6TcnTZ4Vocm2UaK2FBKAJzhBKXOi2ioGd3AtpnGkvd13HM
+-----END PRIVATE KEY-----