image: Add signing infrastructure

Add a structure to describe an algorithm which can sign and (later) verify
images.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/image-sig.c b/common/image-sig.c
new file mode 100644
index 0000000..841c662
--- /dev/null
+++ b/common/image-sig.c
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2013, Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifdef USE_HOSTCC
+#include "mkimage.h"
+#include <time.h>
+#else
+#include <common.h>
+#endif /* !USE_HOSTCC*/
+#include <errno.h>
+#include <image.h>
+
+struct image_sig_algo image_sig_algos[] = {
+};
+
+struct image_sig_algo *image_get_sig_algo(const char *name)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(image_sig_algos); i++) {
+		if (!strcmp(image_sig_algos[i].name, name))
+			return &image_sig_algos[i];
+	}
+
+	return NULL;
+}