diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index 20ffaf0cd..1a3b40e4d 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -572,6 +572,20 @@ enum TALER_AmlDecisionState
 };
 
 
+/**
+ * Possible algorithms for confirmation code generation.
+ */
+enum TALER_MerchantConfirmationAlgorithm
+{
+
+  /**
+   * No purchase confirmation.
+   */
+  TALER_MCA_NONE = 0
+
+};
+
+
 /**
  * @brief Type of blinding keys for Taler.
  * must be 32 bytes (DB)
@@ -914,6 +928,16 @@ struct TALER_GlobalFeeSetNBOP
 GNUNET_NETWORK_STRUCT_END
 
 
+/**
+ * FIXME.
+ */
+char *
+TALER_build_pos_confirmation (const char *pos_key,
+                              enum TALER_MerchantConfirmationAlgorithm pos_alg,
+                              const struct TALER_Amount *total,
+                              struct GNUNET_TIME_Timestamp ts);
+
+
 /**
  * Set of the fees applying to a denomination.
  */
diff --git a/src/util/Makefile.am b/src/util/Makefile.am
index 656da7c49..115ea5055 100644
--- a/src/util/Makefile.am
+++ b/src/util/Makefile.am
@@ -81,6 +81,7 @@ libtalerutil_la_SOURCES = \
   auditor_signatures.c \
   config.c \
   crypto.c \
+  crypto_confirmation.c \
   crypto_contract.c \
   crypto_helper_common.c crypto_helper_common.h \
   crypto_helper_rsa.c \
diff --git a/src/util/crypto_confirmation.c b/src/util/crypto_confirmation.c
new file mode 100644
index 000000000..61a73f4c2
--- /dev/null
+++ b/src/util/crypto_confirmation.c
@@ -0,0 +1,39 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2023 Taler Systems SA
+
+  TALER 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 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 General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file util/crypto_confirmation.c
+ * @brief confirmation computation
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler_util.h"
+#include <gcrypt.h>
+
+
+char *
+TALER_build_pos_confirmation (const char *pos_key,
+                              enum TALER_MerchantConfirmationAlgorithm pos_alg,
+                              const struct TALER_Amount *total,
+                              struct GNUNET_TIME_Timestamp ts)
+{
+  switch (pos_alg)
+  {
+  case TALER_MCA_NONE:
+    return NULL;
+  }
+  GNUNET_break (0); // FIXME: not implemented
+  return NULL;
+}