WiP: age-withdraw, added TALER_age_restriction_commit_from_base, 6/n

Added TALER_age_restriction_commit_from_base in util/age_restriction.c,
to create a age commitment and proof from a coin's private key as
defined in
https://docs.taler.net/core/api-exchange.html#withdraw-with-age-restriction

contrib/gana

@@ -1 +1 @@
-Subproject commit 02132ededc12a0a1cfd81f0ca76c384304e15259
+Subproject commit 1ec4596bf4925ee24fc06d3e74d2a553b8239870

debian/taler-exchange.taler-exchange-httpd.service

@@ -8,11 +8,19 @@ PartOf=taler-exchange.target
 [Service]
 User=taler-exchange-httpd
 Type=simple
-# Depending on the configuration, the service suicides and then
-# needs to be restarted.
+
+# Depending on the configuration, the service process kills itself and then
+# needs to be restarted. Thus no significant delay on restarts.
 Restart=always
-# Do not dally on restarts.
 RestartSec=1ms
+
+# Disable the service if more than 5 restarts are encountered within 5s.
+# These are usually the systemd defaults, but can be overwritten, thus we set
+# them here explicitly, as the exchange code assumes StartLimitInterval
+# to be >=5s.
+StartLimitBurst=5
+StartLimitInterval=5s
+
 ExecStart=/usr/bin/taler-exchange-httpd -c /etc/taler/taler.conf
 StandardOutput=journal
 StandardError=journal

src/bank-lib/bank_api_credit.c

@@ -248,12 +248,15 @@ TALER_BANK_credit_history (struct GNUNET_CURL_Context *ctx,
   {
     if ( (0 < num_results) &&
          (! GNUNET_TIME_relative_is_zero (timeout)) )
+      /* 0 == start_row is implied, go with timeout into future */
       GNUNET_snprintf (url,
                        sizeof (url),
                        "history/incoming?delta=%lld&long_poll_ms=%llu",
                        (long long) num_results,
                        tms);
     else
+      /* Going back from current transaction or have no timeout;
+         hence timeout makes no sense */
       GNUNET_snprintf (url,
                        sizeof (url),
                        "history/incoming?delta=%lld",
@@ -263,6 +266,7 @@ TALER_BANK_credit_history (struct GNUNET_CURL_Context *ctx,
   {
     if ( (0 < num_results) &&
          (! GNUNET_TIME_relative_is_zero (timeout)) )
+      /* going forward from num_result */
       GNUNET_snprintf (url,
                        sizeof (url),
                        "history/incoming?delta=%lld&start=%llu&long_poll_ms=%llu",
@@ -270,6 +274,8 @@ TALER_BANK_credit_history (struct GNUNET_CURL_Context *ctx,
                        (unsigned long long) start_row,
                        tms);
     else
+      /* going backwards or have no timeout;
+         hence timeout makes no sense */
       GNUNET_snprintf (url,
                        sizeof (url),
                        "history/incoming?delta=%lld&start=%llu",

src/exchange/taler-exchange-httpd.c

@@ -80,6 +80,11 @@
  */
 #define UNIX_BACKLOG 50
 
+/**
+ * How often will we try to connect to the database before giving up?
+ */
+#define MAX_DB_RETRIES 5
+
 /**
  * Above what request latency do we start to log?
  */
@@ -1965,11 +1970,20 @@ exchange_serve_process_config (void)
     GNUNET_free (attr_enc_key_str);
   }
 
-  if (NULL ==
-      (TEH_plugin = TALER_EXCHANGEDB_plugin_load (TEH_cfg)))
+  for (unsigned int i = 0; i<MAX_DB_RETRIES; i++)
+  {
+    TEH_plugin = TALER_EXCHANGEDB_plugin_load (TEH_cfg);
+    if (NULL != TEH_plugin)
+      break;
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Failed to connect to DB, will try again %u times\n",
+                MAX_DB_RETRIES - i);
+    sleep (1);
+  }
+  if (NULL == TEH_plugin)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failed to initialize DB subsystem\n");
+                "Failed to initialize DB subsystem. Giving up.\n");
     return GNUNET_SYSERR;
   }
   return GNUNET_OK;

src/exchange/taler-exchange-httpd_age-withdraw_reveal.c

@@ -28,22 +28,6 @@
 #include "taler-exchange-httpd_responses.h"
 #include "taler-exchange-httpd_keys.h"
 
-/**
- * Clients have to prove that the public keys for all age groups larger than
- * the allowed maximum age group are derived by scalar multiplication from this
- * Edx25519 public key (in Crockford Base32 encoding):
- *
- *       DZJRF6HXN520505XDAWM8NMH36QV9J3VH77265WQ09EBQ76QSKCG
- *
- * The private key was chosen randomly and then deleted.
- */
-static struct GNUNET_CRYPTO_Edx25519PublicKey publishedBaseKey = {
-  .q_y = { 0x6f, 0xe5, 0x87, 0x9a, 0x3d, 0xa9, 0x44, 0x20,
-           0x80, 0xbd, 0x6a, 0xb9, 0x44, 0x56, 0x91, 0x19,
-           0xaf, 0xb4, 0xc8, 0x7b, 0x89, 0xce, 0x23, 0x17,
-           0x97, 0x20, 0x5c, 0xbb, 0x9c, 0xd7, 0xcc, 0xd9},
-};
-
 /**
  * State for an /age-withdraw/$ACH/reveal operation.
  */
@@ -360,17 +344,15 @@ denomination_is_valid (
     connection,
     result);
 
-  /* Does the denomination exist? */
   if (NULL == dks)
   {
+    /* The denomination doesn't exist */
     GNUNET_assert (result != NULL);
     /* Note: a HTTP-response has been queued and result has been set by
      * TEH_keys_denominations_by_hash2 */
     return false;
   }
 
-  /* Is the denomation still and already valid? */
-
   if (GNUNET_TIME_absolute_is_past (dks->meta.expire_withdraw.abs_time))
   {
     /* This denomination is past the expiration time for withdraws */
@@ -582,6 +564,7 @@ verify_commitment_and_max_age (
   for (uint32_t i = 0; i < num_coins; i++)
   {
     /* FIXME:oec:  Calculate new coins and blinded hashes */
+    /*TALER_age_restriction_commit_from_base(); */
   }
 
   return GNUNET_SYSERR;

src/exchange/taler-exchange-httpd_csr.c

@@ -234,12 +234,10 @@ TEH_handler_csr_withdraw (struct TEH_RequestContext *rc,
     .cipher = TALER_DENOMINATION_CS
   };
   struct GNUNET_JSON_Specification spec[] = {
-    GNUNET_JSON_spec_fixed ("nonce",
-                            &nonce,
-                            sizeof (struct TALER_CsNonce)),
-    GNUNET_JSON_spec_fixed ("denom_pub_hash",
-                            &denom_pub_hash,
-                            sizeof (struct TALER_DenominationHashP)),
+    GNUNET_JSON_spec_fixed_auto ("nonce",
+                                 &nonce),
+    GNUNET_JSON_spec_fixed_auto ("denom_pub_hash",
+                                 &denom_pub_hash),
     GNUNET_JSON_spec_end ()
   };
   struct TEH_DenominationKey *dk;
@@ -333,17 +331,11 @@ TEH_handler_csr_withdraw (struct TEH_RequestContext *rc,
     }
   }
 
-  {
-    json_t *csr_obj;
-
-    csr_obj = GNUNET_JSON_PACK (
-      TALER_JSON_pack_exchange_withdraw_values ("ewv",
-                                                &ewv));
-    GNUNET_assert (NULL != csr_obj);
-    return TALER_MHD_reply_json_steal (rc->connection,
-                                       csr_obj,
-                                       MHD_HTTP_OK);
-  }
+  return TALER_MHD_REPLY_JSON_PACK (
+    rc->connection,
+    MHD_HTTP_OK,
+    TALER_JSON_pack_exchange_withdraw_values ("ewv",
+                                              &ewv));
 }
 
 

src/exchange/taler-exchange-httpd_keys.c

@@ -738,7 +738,7 @@ free_denom_cb (void *cls,
  * @param value the `struct HelperSignkey` to release
  * @return #GNUNET_OK (continue to iterate)
  */
-static int
+static enum GNUNET_GenericReturnValue
 free_esign_cb (void *cls,
                const struct GNUNET_PeerIdentity *pid,
                void *value)
@@ -3616,6 +3616,7 @@ TEH_keys_management_get_keys_handler (const struct TEH_RequestHandler *rh,
     if ( (GNUNET_is_zero (&denom_rsa_sm_pub)) &&
          (GNUNET_is_zero (&denom_cs_sm_pub)) )
     {
+      /* Either IPC failed, or neither helper had any denominations configured. */
       return TALER_MHD_reply_with_error (connection,
                                          MHD_HTTP_BAD_GATEWAY,
                                          TALER_EC_EXCHANGE_DENOMINATION_HELPER_UNAVAILABLE,
@@ -3628,7 +3629,6 @@ TEH_keys_management_get_keys_handler (const struct TEH_RequestHandler *rh,
                                          TALER_EC_EXCHANGE_SIGNKEY_HELPER_UNAVAILABLE,
                                          NULL);
     }
-    // then a secmod helper is not yet running and we should return an MHD_HTTP_BAD_GATEWAY!
     GNUNET_assert (NULL != fbc.denoms);
     GNUNET_assert (NULL != fbc.signkeys);
     GNUNET_CONTAINER_multihashmap_iterate (ksh->helpers->denom_keys,

src/exchange/taler-exchange-wirewatch.c

@@ -757,7 +757,7 @@ continue_with_shard (void *cls)
                       shard_end - latest_row_off);
   GNUNET_assert (NULL == hh);
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Requesting credit history staring from %llu\n",
+              "Requesting credit history starting from %llu\n",
               (unsigned long long) latest_row_off);
   hh_start_time = GNUNET_TIME_absolute_get ();
   hh_returned_data = false;

src/include/taler_crypto_lib.h

@@ -18,6 +18,7 @@
  * @brief taler-specific crypto functions
  * @author Sree Harsha Totakura <sreeharsha@totakura.in>
  * @author Christian Grothoff <christian@grothoff.org>
+ * @author Özgür Kesim <oec-taler@kesim.org>
  */
 #if ! defined (__TALER_UTIL_LIB_H_INSIDE__)
 #error "Only <taler_util.h> can be included directly."
@@ -5926,4 +5927,42 @@ void
 TALER_age_commitment_proof_free (
   struct TALER_AgeCommitmentProof *p);
 
+
+/**
+ * @brief For age-withdraw, clients have to prove that the public keys for all
+ * age groups larger than the allowed maximum age group are derived by scalar
+ * multiplication from this Edx25519 public key (in Crockford Base32 encoding):
+ *
+ *       DZJRF6HXN520505XDAWM8NMH36QV9J3VH77265WQ09EBQ76QSKCG
+ *
+ * Its private key was chosen randomly and then deleted.
+ */
+extern struct
+#ifndef AGE_RESTRICTION_WITH_ECDSA
+GNUNET_CRYPTO_Edx25519PublicKey
+#else
+GNUNET_CRYPTO_EcdsaPublicKey
+#endif
+TALER_age_commitment_base_public_key;
+
+/**
+ * @brief Similiar to TALER_age_restriction_commit, but takes the coin's
+ * private key as seed input and calculates the public keys in the slots larger
+ * than the given age as derived from TALER_age_commitment_base_public_key.
+ *
+ * See https://docs.taler.net/core/api-exchange.html#withdraw-with-age-restriction
+ *
+ * @param mask The age mask, defining the age groups
+ * @param max_age The maximum age for this coin.
+ * @param coin_priv The private key of the coin from which we derive the age restriction
+ * @param[out] comm_proof The commitment and proof for age restriction for age @a max_age
+ */
+enum GNUNET_GenericReturnValue
+TALER_age_restriction_commit_from_base (
+  const struct TALER_CoinSpendPrivateKeyP *coin_priv,
+  const struct TALER_AgeMask *mask,
+  uint8_t max_age,
+  struct TALER_AgeCommitmentProof *comm_proof);
+
+
 #endif

src/lib/exchange_api_reserves_get.c

@@ -168,9 +168,10 @@ handle_reserves_get_finished (void *cls,
     rs.hr.ec = TALER_JSON_get_error_code (j);
     rs.hr.hint = TALER_JSON_get_error_hint (j);
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Unexpected response code %u/%d for reserves get\n",
+                "Unexpected response code %u/%d for GET %s\n",
                 (unsigned int) response_code,
-                (int) rs.hr.ec);
+                (int) rs.hr.ec,
+                rgh->url);
     break;
   }
   if (NULL != rgh->cb)

src/util/age_restriction.c

@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2022 Taler Systems SA
+  Copyright (C) 2022-2023 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
@@ -24,6 +24,19 @@
 #include <gnunet/gnunet_json_lib.h>
 #include <gcrypt.h>
 
+struct
+#ifndef AGE_RESTRICTION_WITH_ECDSA
+GNUNET_CRYPTO_Edx25519PublicKey
+#else
+GNUNET_CRYPTO_EcdsaPublicKey
+#endif
+TALER_age_commitment_base_public_key = {
+  .q_y = { 0x6f, 0xe5, 0x87, 0x9a, 0x3d, 0xa9, 0x44, 0x20,
+           0x80, 0xbd, 0x6a, 0xb9, 0x44, 0x56, 0x91, 0x19,
+           0xaf, 0xb4, 0xc8, 0x7b, 0x89, 0xce, 0x23, 0x17,
+           0x97, 0x20, 0x5c, 0xbb, 0x9c, 0xd7, 0xcc, 0xd9},
+};
+
 void
 TALER_age_commitment_hash (
   const struct TALER_AgeCommitment *commitment,
@@ -82,36 +95,78 @@ get_age_group (
 }
 
 
+#ifdef AGE_RESTRICTION_WITH_ECDSA
+/* @brief Helper function to generate a ECDSA private key
+ *
+ * @param seed Input seed
+ * @param size Size of the seed in bytes
+ * @param[out] pkey ECDSA private key
+ * @return GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+ecdsa_create_from_seed (
+  const void *seed,
+  size_t seed_size,
+  struct GNUNET_CRYPTO_EcdsaPrivateKey *key)
+{
+  enum GNUNET_GenericReturnValue ret;
+  ret = GNUNET_CRYPTO_kdf (key,
+                           sizeof (*key),
+                           &seed,
+                           seed_size,
+                           "age commitment",
+                           sizeof ("age commitment") - 1,
+                           NULL, 0);
+  if (GNUNET_OK != ret)
+    return ret;
+
+  /* See GNUNET_CRYPTO_ecdsa_key_create */
+  key->d[0] &= 248;
+  key->d[31] &= 127;
+  key->d[31] |= 64;
+
+  return GNUNET_OK;
+}
+
+
+#endif
+
+
 enum GNUNET_GenericReturnValue
 TALER_age_restriction_commit (
   const struct TALER_AgeMask *mask,
   const uint8_t age,
   const struct GNUNET_HashCode *seed,
-  struct TALER_AgeCommitmentProof *new)
+  struct TALER_AgeCommitmentProof *ncp)
 {
   struct GNUNET_HashCode seed_i;
-  uint8_t num_pub = __builtin_popcount (mask->bits) - 1;
-  uint8_t num_priv = get_age_group (mask, age);
+  uint8_t num_pub;
+  uint8_t num_priv;
   size_t i;
 
+  GNUNET_assert (NULL != mask);
   GNUNET_assert (NULL != seed);
-  GNUNET_assert (NULL != new);
+  GNUNET_assert (NULL != ncp);
   GNUNET_assert (mask->bits & 1); /* fist bit must have been set */
+
+  num_pub = __builtin_popcount (mask->bits) - 1;
+  num_priv = get_age_group (mask, age);
+
   GNUNET_assert (31 > num_priv);
   GNUNET_assert (num_priv <= num_pub);
 
   seed_i = *seed;
-  new->commitment.mask.bits = mask->bits;
-  new->commitment.num = num_pub;
-  new->proof.num = num_priv;
-  new->proof.keys = NULL;
+  ncp->commitment.mask.bits = mask->bits;
+  ncp->commitment.num = num_pub;
+  ncp->proof.num = num_priv;
+  ncp->proof.keys = NULL;
 
-  new->commitment.keys = GNUNET_new_array (
+  ncp->commitment.keys = GNUNET_new_array (
     num_pub,
     struct TALER_AgeCommitmentPublicKeyP);
 
   if (0 < num_priv)
-    new->proof.keys = GNUNET_new_array (
+    ncp->proof.keys = GNUNET_new_array (
       num_priv,
       struct TALER_AgeCommitmentPrivateKeyP);
 
@@ -126,47 +181,33 @@ TALER_age_restriction_commit (
 
     /* Only save the private keys for age groups less than num_priv */
     if (i < num_priv)
-      pkey = &new->proof.keys[i];
+      pkey = &ncp->proof.keys[i];
 
 #ifndef AGE_RESTRICTION_WITH_ECDSA
     GNUNET_CRYPTO_edx25519_key_create_from_seed (&seed_i,
                                                  sizeof(seed_i),
                                                  &pkey->priv);
     GNUNET_CRYPTO_edx25519_key_get_public (&pkey->priv,
-                                           &new->commitment.keys[i].pub);
+                                           &ncp->commitment.keys[i].pub);
+#else
+    if (GNUNET_OK !=
+        ecdsa_create_from_seed (&seed_i,
+                                sizeof(seed_i),
+                                &pkey->priv))
+    {
+      GNUNET_free (ncp->commitment.keys);
+      GNUNET_free (ncp->proof.keys);
+      return GNUNET_SYSERR;
+    }
+
+    GNUNET_CRYPTO_ecdsa_key_get_public (&pkey->priv,
+                                        &ncp->commitment.keys[i].pub);
+#endif
+
     seed_i.bits[0] += 1;
   }
 
   return GNUNET_OK;
-#else
-    if  (GNUNET_OK !=
-         GNUNET_CRYPTO_kdf (pkey,
-                            sizeof (*pkey),
-                            &salti,
-                            sizeof (salti),
-                            "age commitment",
-                            strlen ("age commitment"),
-                            NULL, 0))
-      goto FAIL;
-
-    /* See GNUNET_CRYPTO_ecdsa_key_create */
-    pkey->priv.d[0] &= 248;
-    pkey->priv.d[31] &= 127;
-    pkey->priv.d[31] |= 64;
-
-    GNUNET_CRYPTO_ecdsa_key_get_public (&pkey->priv,
-                                        &new->commitment.keys[i].pub);
-
-  }
-
-  return GNUNET_OK;
-
-FAIL:
-  GNUNET_free (new->commitment.keys);
-  if (NULL != new->proof.keys)
-    GNUNET_free (new->proof.keys);
-  return GNUNET_SYSERR;
-#endif
 }
 
 
@@ -216,33 +257,30 @@ TALER_age_commitment_derive (
       &newacp->proof.keys[i].priv);
   }
 #else
-  char label[sizeof(uint64_t) + 1] = {0};
-
-  /* Because GNUNET_CRYPTO_ecdsa_public_key_derive expects char * (and calls
-   * strlen on it), we must avoid 0's in the label.  */
-  uint64_t nz_salt = salt | 0x8040201008040201;
-  memcpy (label, &nz_salt, sizeof(nz_salt));
-
-  /* 1. Derive the public keys */
-  for (size_t i = 0; i < orig->commitment.num; i++)
   {
-    GNUNET_CRYPTO_ecdsa_public_key_derive (
-      &orig->commitment.keys[i].pub,
-      label,
-      "age commitment derive",
-      &newacp->commitment.keys[i].pub);
-  }
+    const char *label = GNUNET_h2s (salt);
 
-  /* 2. Derive the private keys */
-  for (size_t i = 0; i < orig->proof.num; i++)
-  {
-    struct GNUNET_CRYPTO_EcdsaPrivateKey *priv;
-    priv = GNUNET_CRYPTO_ecdsa_private_key_derive (
-      &orig->proof.keys[i].priv,
-      label,
-      "age commitment derive");
-    newacp->proof.keys[i].priv = *priv;
-    GNUNET_free (priv);
+    /* 1. Derive the public keys */
+    for (size_t i = 0; i < orig->commitment.num; i++)
+    {
+      GNUNET_CRYPTO_ecdsa_public_key_derive (
+        &orig->commitment.keys[i].pub,
+        label,
+        "age commitment derive",
+        &newacp->commitment.keys[i].pub);
+    }
+
+    /* 2. Derive the private keys */
+    for (size_t i = 0; i < orig->proof.num; i++)
+    {
+      struct GNUNET_CRYPTO_EcdsaPrivateKey *priv;
+      priv = GNUNET_CRYPTO_ecdsa_private_key_derive (
+        &orig->proof.keys[i].priv,
+        label,
+        "age commitment derive");
+      newacp->proof.keys[i].priv = *priv;
+      GNUNET_free (priv);
+    }
   }
 #endif
 
@@ -546,4 +584,106 @@ TALER_age_mask_to_string (
 }
 
 
+enum GNUNET_GenericReturnValue
+TALER_age_restriction_commit_from_base (
+  const struct TALER_CoinSpendPrivateKeyP *coin_priv,
+  const struct TALER_AgeMask *mask,
+  uint8_t max_age,
+  struct TALER_AgeCommitmentProof *ncp)
+{
+  struct GNUNET_HashCode seed_i = {0};
+  uint8_t num_pub;
+  uint8_t num_priv;
+
+  GNUNET_assert (NULL != mask);
+  GNUNET_assert (NULL != coin_priv);
+  GNUNET_assert (NULL != ncp);
+  GNUNET_assert (mask->bits & 1); /* fist bit must have been set */
+
+  num_pub = __builtin_popcount (mask->bits) - 1;
+  num_priv = get_age_group (mask, max_age);
+
+  GNUNET_assert (31 > num_priv);
+  GNUNET_assert (num_priv <= num_pub);
+
+  ncp->commitment.mask.bits = mask->bits;
+  ncp->commitment.num = num_pub;
+  ncp->proof.num = num_priv;
+  ncp->proof.keys = NULL;
+
+  ncp->commitment.keys = GNUNET_new_array (
+    num_pub,
+    struct TALER_AgeCommitmentPublicKeyP);
+
+  if (0 < num_priv)
+    ncp->proof.keys = GNUNET_new_array (
+      num_priv,
+      struct TALER_AgeCommitmentPrivateKeyP);
+
+  /* Create as many private keys as allow with max_age and derive the
+   * corresponding public keys.  The rest of the needed public keys are created
+   * by scalar mulitplication with the TALER_age_commitment_base_public_key. */
+  for (size_t i = 0; i < num_pub; i++)
+  {
+    enum GNUNET_GenericReturnValue ret;
+    const char *label = i < num_priv ? "age-commitment" : "age-factor";
+
+    ret = GNUNET_CRYPTO_kdf (&seed_i, sizeof(seed_i),
+                             coin_priv, sizeof(*coin_priv),
+                             label, strlen (label),
+                             &i, sizeof(i),
+                             NULL, 0);
+    GNUNET_assert (GNUNET_OK == ret);
+
+    /* Only generate and save the private keys and public keys for age groups
+     * less than num_priv */
+    if (i < num_priv)
+    {
+      struct TALER_AgeCommitmentPrivateKeyP *pkey = &ncp->proof.keys[i];
+
+#ifndef AGE_RESTRICTION_WITH_ECDSA
+      GNUNET_CRYPTO_edx25519_key_create_from_seed (&seed_i,
+                                                   sizeof(seed_i),
+                                                   &pkey->priv);
+      GNUNET_CRYPTO_edx25519_key_get_public (&pkey->priv,
+                                             &ncp->commitment.keys[i].pub);
+#else
+      if (GNUNET_OK != ecdsa_create_from_seed (&seed_i,
+                                               sizeof(seed_i),
+                                               &pkey->priv))
+      {
+        GNUNET_free (ncp->commitment.keys);
+        GNUNET_free (ncp->proof.keys);
+        return GNUNET_SYSERR;
+      }
+      GNUNET_CRYPTO_ecdsa_key_get_public (&pkey->priv,
+                                          &ncp->commitment.keys[i].pub);
+#endif
+    }
+    else
+    {
+      /* For all indices larger than num_priv, derive a public key from
+       * TALER_age_commitment_base_public_key by scalar multiplication */
+#ifndef AGE_RESTRICTION_WITH_ECDSA
+      GNUNET_CRYPTO_edx25519_public_key_derive (
+        &TALER_age_commitment_base_public_key,
+        &seed_i,
+        sizeof(seed_i),
+        &ncp->commitment.keys[i].pub);
+#else
+
+      GNUNET_CRYPTO_ecdsa_public_key_derive (
+        &TALER_age_commitment_base_public_key,
+        GNUNET_h2s (&seed_i),
+        "age withdraw",
+        &ncp->commitment.keys[i].pub);
+#endif
+    }
+  }
+
+  return GNUNET_OK;
+
+}
+
+
 /* end util/age_restriction.c */