diff --git a/src/include/b64_decode.h b/src/include/b64_decode.h
new file mode 100644
index 0000000..b527196
--- /dev/null
+++ b/src/include/b64_decode.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2015 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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.
+ */
+
+#ifndef __INCLUDE_B64_DECODE_H__
+#define __INCLUDE_B64_DECODE_H__
+
+#include <stddef.h>
+#include <stdint.h>
+
+/*
+ * A function to convert a buffer of base64 format data into its source.
+ *
+ * The user provides output buffer of the size guaranteed to fit the result.
+ *
+ * Returns the size of the decoded data or zero if invalid charactes were
+ * encountered in the input buffer.
+ */
+size_t b64_decode(const uint8_t *input_data,
+		  size_t input_length,
+		  uint8_t *output_data);
+
+/* A macro to derive decoded size of a base64 encoded blob. */
+#define B64_DECODED_SIZE(encoded_size) (((encoded_size) * 3)/4)
+
+#endif