From 34e71cce0c9f7d7c6c92805ada14b627396bb9b3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=96zg=C3=BCr=20Kesim?= <oec-taler@kesim.org>
Date: Sun, 30 Jan 2022 14:18:04 +0100
Subject: [PATCH] [WIP - DOESN'T COMPILE] age_commitment_hash added

---
 src/include/taler_crypto_lib.h | 24 ++++++++++++++++++++++++
 src/util/crypto.c              | 30 ++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index ab69d4dfb..069c0d3ca 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -317,6 +317,30 @@ extern const struct TALER_AgeHash TALER_AgeHash_zeroHash;
                                                       &TALER_AgeHash_zeroHash, \
                                                       sizeof(struct \
                                                              TALER_AgeHash))))
+/*
+ * @brief Representation of an age commitment:  one public key per age group.
+ *
+ * The number of keys must be be the same as the number of bits set in the
+ * corresponding age mask.
+ */
+struct TALER_AgeCommitment
+{
+  struct TALER_AgeMask mask;
+  struct GNUNET_CRYPTO_EddsaPublicKey *keys;
+  size_t num_keys;
+};
+
+
+/*
+ * @brief Generates a hash of the public keys in the age commitment.
+ * @param commitment the age commitment - one public key per age group
+ * @param[out] hash resulting hash
+ */
+void
+TALER_age_commitment_hash (
+  const struct TALER_AgeCommitment *commitment,
+  struct TALER_AgeHash *hash);
+
 
 /**
  * @brief Type of public keys for Taler coins.  The same key material is used
diff --git a/src/util/crypto.c b/src/util/crypto.c
index 817ad3cd7..c0ad07387 100644
--- a/src/util/crypto.c
+++ b/src/util/crypto.c
@@ -20,6 +20,7 @@
  * @author Florian Dold
  * @author Benedikt Mueller
  * @author Christian Grothoff
+ * @author Özgür Kesim
  */
 #include "platform.h"
 #include "taler_util.h"
@@ -356,4 +357,33 @@ TALER_coin_pub_hash (const struct TALER_CoinSpendPublicKeyP *coin_pub,
 }
 
 
+void
+TALER_age_commitment_hash (
+  const struct TALER_AgeCommitment *commitment,
+  struct TALER_AgeHash *ahash)
+{
+  struct GNUNET_HashContext *hash_context;
+  struct GNUNET_HashCode hash;
+  GNUNET_assert (NULL != commitment);
+  GNUNET_assert (__builtin_popcount (commitment->mask.mask) ==
+                 commitment->num_keys);
+
+  hash_context = GNUNET_CRYPTO_hash_context_start ();
+
+  for (size_t i = 0; i < commitment->num_keys; i++)
+  {
+    GNUNET_CRYPTO_hash_context_read (hash_context,
+                                     &commitment->keys[i],
+                                     sizeof(struct
+                                            GNUNET_CRYPTO_EddsaPublicKey));
+  }
+
+  GNUNET_CRYPTO_hash_context_finish (hash_context,
+                                     &hash);
+  GNUNET_memcpy (&ahash->shash.bits,
+                 &hash.bits,
+                 sizeof(ahash->shash.bits));
+}
+
+
 /* end of crypto.c */