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diff --git a/src/lib/exchange_api_refresh_common.h b/src/lib/exchange_api_refresh_common.h
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+++ b/src/lib/exchange_api_refresh_common.h
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+/*
+  This file is part of TALER
+  Copyright (C) 2015-2022 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 lib/exchange_api_refresh_common.h
+ * @brief shared (serialization) logic for refresh protocol
+ * @author Christian Grothoff
+ */
+#ifndef REFRESH_COMMON_H
+#define REFRESH_COMMON_H
+#include <jansson.h>
+#include "taler_json_lib.h"
+#include "taler_exchange_service.h"
+#include "taler_signatures.h"
+
+
+/**
+ * Information about a coin we are melting.
+ */
+struct MeltedCoin
+{
+  /**
+   * Private key of the coin.
+   */
+  struct TALER_CoinSpendPrivateKeyP coin_priv;
+
+  /**
+   * Amount this coin contributes to the melt, including fee.
+   */
+  struct TALER_Amount melt_amount_with_fee;
+
+  /**
+   * The applicable fee for melting a coin of this denomination
+   */
+  struct TALER_Amount fee_melt;
+
+  /**
+   * The original value of the coin.
+   */
+  struct TALER_Amount original_value;
+
+  /**
+   * The original age commitment, its proof and its hash.  MUST be NULL if no
+   * age commitment was set.
+   */
+  const struct TALER_AgeCommitmentProof *age_commitment_proof;
+  const struct TALER_AgeCommitmentHash *h_age_commitment;
+
+  /**
+   * Timestamp indicating when coins of this denomination become invalid.
+   */
+  struct GNUNET_TIME_Timestamp expire_deposit;
+
+  /**
+   * Denomination key of the original coin.
+   */
+  struct TALER_DenominationPublicKey pub_key;
+
+  /**
+   * Exchange's signature over the coin.
+   */
+  struct TALER_DenominationSignature sig;
+
+};
+
+
+/**
+ * Data we keep for each fresh coin created in the
+ * melt process.
+ */
+struct FreshCoinData
+{
+  /**
+   * Denomination public key of the coin.
+   */
+  struct TALER_DenominationPublicKey fresh_pk;
+
+  /**
+   * Array of planchet secrets for the coins, depending
+   * on the cut-and-choose.
+   */
+  struct TALER_PlanchetMasterSecretP ps[TALER_CNC_KAPPA];
+
+  /**
+   * Private key of the coin.
+   */
+  struct TALER_CoinSpendPrivateKeyP coin_priv;
+
+  /**
+   * Arrays of age commitments and proofs to be created, one for each
+   * cut-and-choose dimension.  NULL if age restriction is not applicable.
+   */
+  struct TALER_AgeCommitmentProof *age_commitment_proofs[TALER_CNC_KAPPA];
+
+  /**
+   * Blinding key secrets for the coins, depending on the
+   * cut-and-choose.
+   */
+  union TALER_DenominationBlindingKeyP bks[TALER_CNC_KAPPA];
+
+};
+
+
+/**
+ * Melt data in non-serialized format for convenient processing.
+ */
+struct MeltData
+{
+
+  /**
+   * Hash over the committed data during refresh operation.
+   */
+  struct TALER_RefreshCommitmentP rc;
+
+  /**
+   * Information about the melted coin.
+   */
+  struct MeltedCoin melted_coin;
+
+  /**
+   * Array of length @e num_fresh_coins with information
+   * about each fresh coin.
+   */
+  struct FreshCoinData *fcds;
+
+  /**
+   * Transfer secrets, one per cut and choose.
+   */
+  struct TALER_TransferSecretP trans_sec[TALER_CNC_KAPPA];
+
+  /**
+   * Transfer private keys for each cut-and-choose dimension.
+   */
+  struct TALER_TransferPrivateKeyP transfer_priv[TALER_CNC_KAPPA];
+
+  /**
+   * Transfer public key of this commitment.
+   */
+  struct TALER_TransferPublicKeyP transfer_pub[TALER_CNC_KAPPA];
+
+  /**
+   * Transfer secrets, one per cut and choose.
+   */
+  struct TALER_RefreshCommitmentEntry rce[TALER_CNC_KAPPA];
+
+  /**
+   * Blinded planchets and denominations of the fresh coins, depending on the cut-and-choose.  Array of length
+   * @e num_fresh_coins.
+   */
+  struct TALER_RefreshCoinData *rcd[TALER_CNC_KAPPA];
+
+  /**
+   * Number of coins we are creating
+   */
+  uint16_t num_fresh_coins;
+
+};
+
+
+/**
+ * Compute the melt data from the refresh data and secret.
+ *
+ * @param rms secret internals of the refresh-reveal operation
+ * @param rd refresh data with the characteristics of the operation
+ * @param alg_values contributions from the exchange into the melt
+ * @param[out] md where to write the derived melt data
+ */
+enum GNUNET_GenericReturnValue
+TALER_EXCHANGE_get_melt_data_ (
+  const struct TALER_RefreshMasterSecretP *rms,
+  const struct TALER_EXCHANGE_RefreshData *rd,
+  const struct TALER_ExchangeWithdrawValues *alg_values,
+  struct MeltData *md);
+
+
+/**
+ * Free all information associated with a melting session.  Note
+ * that we allow the melting session to be only partially initialized,
+ * as we use this function also when freeing melt data that was not
+ * fully initialized.
+ *
+ * @param[in] md melting data to release, the pointer itself is NOT
+ *           freed (as it is typically not allocated by itself)
+ */
+void
+TALER_EXCHANGE_free_melt_data_ (struct MeltData *md);
+
+#endif