diff --git a/src/auditor-lib/auditor_api_handle.c b/src/auditor-lib/auditor_api_handle.c
index 4db528a31..9e4f73486 100644
--- a/src/auditor-lib/auditor_api_handle.c
+++ b/src/auditor-lib/auditor_api_handle.c
@@ -483,7 +483,7 @@ MAH_path_to_url2 (const char *base_url,
struct TALER_AUDITOR_Handle *
TALER_AUDITOR_connect (struct GNUNET_CURL_Context *ctx,
const char *url,
- TALER_AUDITOR_VersionificationCallback version_cb,
+ TALER_AUDITOR_VersionCallback version_cb,
void *version_cb_cls)
{
struct TALER_AUDITOR_Handle *auditor;
diff --git a/src/include/Makefile.am b/src/include/Makefile.am
index 2916a812c..d06d0064a 100644
--- a/src/include/Makefile.am
+++ b/src/include/Makefile.am
@@ -12,6 +12,7 @@ else
talerinclude_HEADERS = \
platform.h \
+ taler_auditor_service.h \
taler_amount_lib.h \
taler_auditordb_lib.h \
taler_auditordb_plugin.h \
diff --git a/src/include/taler_auditor_service.h b/src/include/taler_auditor_service.h
new file mode 100644
index 000000000..a26ecb6f7
--- /dev/null
+++ b/src/include/taler_auditor_service.h
@@ -0,0 +1,159 @@
+/*
+ This file is part of TALER
+ Copyright (C) 2014-2018 Taler Systems SA
+
+ TALER is free software; you can redistribute it and/or modify it under the
+ terms of the GNU Affero General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ TALER 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 Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License along with
+ TALER; see the file COPYING. If not, see
+*/
+/**
+ * @file include/taler_auditor_service.h
+ * @brief C interface of libtalerauditor, a C library to use auditor's HTTP API
+ * @author Sree Harsha Totakura
+ * @author Christian Grothoff
+ */
+#ifndef _TALER_AUDITOR_SERVICE_H
+#define _TALER_AUDITOR_SERVICE_H
+
+#include
+#include "taler_util.h"
+#include "taler_error_codes.h"
+#include
+
+
+/* ********************* /version *********************** */
+
+/**
+ * @brief Information we get from the auditor about auditors.
+ */
+struct TALER_AUDITOR_VersionInformation
+{
+ /**
+ * Public key of the auditing institution. Wallets and merchants
+ * are expected to be configured with a set of public keys of
+ * auditors that they deem acceptable. These public keys are
+ * the roots of the Taler PKI.
+ */
+ struct TALER_AuditorPublicKeyP auditor_pub;
+
+ /**
+ * Supported Taler protocol version by the auditor.
+ * String in the format current:revision:age using the
+ * semantics of GNU libtool. See
+ * https://www.gnu.org/software/libtool/manual/html_node/Versioning.html#Versioning
+ */
+ char *version;
+
+};
+
+
+/**
+ * How compatible are the protocol version of the auditor and this
+ * client? The bits (1,2,4) can be used to test if the auditor's
+ * version is incompatible, older or newer respectively.
+ */
+enum TALER_AUDITOR_VersionCompatibility
+{
+
+ /**
+ * The auditor runs exactly the same protocol version.
+ */
+ TALER_AUDITOR_VC_MATCH = 0,
+
+ /**
+ * The auditor is too old or too new to be compatible with this
+ * implementation (bit)
+ */
+ TALER_AUDITOR_VC_INCOMPATIBLE = 1,
+
+ /**
+ * The auditor is older than this implementation (bit)
+ */
+ TALER_AUDITOR_VC_OLDER = 2,
+
+ /**
+ * The auditor is too old to be compatible with
+ * this implementation.
+ */
+ TALER_AUDITOR_VC_INCOMPATIBLE_OUTDATED
+ = TALER_AUDITOR_VC_INCOMPATIBLE
+ | TALER_AUDITOR_VC_OLDER,
+
+ /**
+ * The auditor is more recent than this implementation (bit).
+ */
+ TALER_AUDITOR_VC_NEWER = 4,
+
+ /**
+ * The auditor is too recent for this implementation.
+ */
+ TALER_AUDITOR_VC_INCOMPATIBLE_NEWER
+ = TALER_AUDITOR_VC_INCOMPATIBLE
+ | TALER_AUDITOR_VC_NEWER,
+
+ /**
+ * We could not even parse the version data.
+ */
+ TALER_AUDITOR_VC_PROTOCOL_ERROR = 8
+
+};
+
+
+/**
+ * Function called with information about the auditor.
+ *
+ * @param cls closure
+ * @param vi basic information about the auditor
+ * @param compat protocol compatibility information
+ */
+typedef void
+(*TALER_AUDITOR_VersionCallback) (void *cls,
+ const struct TALER_AUDITOR_VersionInformation *vi,
+ enum TALER_AUDITOR_VersionCompatibility compat);
+
+
+/**
+ * @brief Handle to the auditor. This is where we interact with
+ * a particular auditor and keep the per-auditor information.
+ */
+struct TALER_AUDITOR_Handle;
+
+
+/**
+ * Initialise a connection to the auditor. Will connect to the
+ * auditor and obtain information about the auditor's master public
+ * key and the auditor's auditor. The respective information will
+ * be passed to the @a version_cb once available, and all future
+ * interactions with the auditor will be checked to be signed
+ * (where appropriate) by the respective master key.
+ *
+ * @param ctx the context
+ * @param url HTTP base URL for the auditor
+ * @param version_cb function to call with the auditor's versionification information
+ * @param version_cb_cls closure for @a version_cb
+ * @return the auditor handle; NULL upon error
+ */
+struct TALER_AUDITOR_Handle *
+TALER_AUDITOR_connect (struct GNUNET_CURL_Context *ctx,
+ const char *url,
+ TALER_AUDITOR_VersionCallback version_cb,
+ void *version_cb_cls);
+
+
+/**
+ * Disconnect from the auditor.
+ *
+ * @param auditor the auditor handle
+ */
+void
+TALER_AUDITOR_disconnect (struct TALER_AUDITOR_Handle *auditor);
+
+
+#endif /* _TALER_AUDITOR_SERVICE_H */