keys: Add sample x25519 priv/pub keys

Signed-off-by: Fabio Utzig <utzig@apache.org>

Author: utzig

enc-x25519-priv.pem

@@ -0,0 +1,3 @@
+-----BEGIN PRIVATE KEY-----
+MC4CAQAwBQYDK2VuBCIEICiAL+/vgpVQ8UGTA2wbuUlsUeUmh493B/i0HwRFbYRP
+-----END PRIVATE KEY-----

enc-x25519-pub.pem

@@ -0,0 +1,3 @@
+-----BEGIN PUBLIC KEY-----
+MCowBQYDK2VuAyEApnrfU1lvc6n45HmsC6ogwvmJkv+Wltehx3CxYYsqD3A=
+-----END PUBLIC KEY-----

sim/mcuboot-sys/csupport/keys.c

@@ -283,3 +283,17 @@ const struct bootutil_key bootutil_enc_key = {
     .len = &enc_key_len,
 };
 #endif
+
+#if defined(MCUBOOT_ENCRYPT_X25519)
+unsigned char enc_key[] = {
+  0x30, 0x2e, 0x02, 0x01, 0x00, 0x30, 0x05, 0x06, 0x03, 0x2b, 0x65, 0x6e,
+  0x04, 0x22, 0x04, 0x20, 0x28, 0x80, 0x2f, 0xef, 0xef, 0x82, 0x95, 0x50,
+  0xf1, 0x41, 0x93, 0x03, 0x6c, 0x1b, 0xb9, 0x49, 0x6c, 0x51, 0xe5, 0x26,
+  0x87, 0x8f, 0x77, 0x07, 0xf8, 0xb4, 0x1f, 0x04, 0x45, 0x6d, 0x84, 0x4f,
+};
+static unsigned int enc_key_len = 48;
+const struct bootutil_key bootutil_enc_key = {
+    .key = enc_key,
+    .len = &enc_key_len,
+};
+#endif