[taler-exchange] 03/37: added CS get R functionality and planchet setup

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gian-demarmels pushed a commit to branch master
in repository exchange.

commit a02ab8f81b68b59ef5228ce30583d9388f9bab4a
Author: Gian Demarmels <gian@demarmels.org>
AuthorDate: Wed Dec 22 12:52:54 2021 +0100

    added CS get R functionality and planchet setup
---
 src/include/taler_crypto_lib.h | 75 +++++++++++++++++++++++++++++-------------
 src/util/crypto.c              | 20 ++++++-----
 src/util/denom.c               | 41 +++++++++++++++++++++++
 src/util/test_crypto.c         | 18 ++++++----
 4 files changed, 117 insertions(+), 37 deletions(-)

diff --git a/src/include/taler_crypto_lib.h b/src/include/taler_crypto_lib.h
index 8e5df1fc..542146cc 100644
--- a/src/include/taler_crypto_lib.h
+++ b/src/include/taler_crypto_lib.h
@@ -794,6 +794,9 @@ struct TALER_BlindedPlanchet
   } details;
 };
 
+/**
+ * Withdraw nonce for CS denominations
+ */
 struct TALER_WithdrawNonce
 {
   /**
@@ -802,6 +805,9 @@ struct TALER_WithdrawNonce
   struct GNUNET_CRYPTO_CsNonce nonce;
 };
 
+/**
+ * Withdraw nonce for CS denominations
+ */
 struct TALER_RefreshNonce
 {
   /**
@@ -810,6 +816,23 @@ struct TALER_RefreshNonce
   struct GNUNET_CRYPTO_CsNonce nonce;
 };
 
+/**
+ * Public R for Cs denominations
+ */
+struct TALER_DenominationCsPublicR
+{
+  struct GNUNET_CRYPTO_CsRPublic r_pub[2];
+};
+
+/**
+ * Secret r for Cs denominations
+ */
+
+struct TALER_DenominationCsPrivateR
+{
+  struct GNUNET_CRYPTO_CsRSecret r[2];
+};
+
 /**
  * @brief RSA Parameters to create blinded messages
  *
@@ -862,28 +885,6 @@ struct TALER_DenominationBlindMessageParams
   } details;
 };
 
-/**
- * @brief CS Blinding Secret parameters to derive blinding secrets
- *
- */
-struct TALER_PlanchetDeriveCsBlindingSecrets
-{
-  /**
-  * Secret to derive blinding secrets from
-  */
-  void *secret;
-
-  /**
-   * size of the secret to derive blinding secrets from
-   */
-  size_t secret_len;
-
-  /**
-   * public R_0 and R_1 are hashed too
-   */
-  struct GNUNET_CRYPTO_CsRPublic r_pub[2];
-};
-
 /**
  * @brief Public information about a coin (including the public key
  * of the coin, the denomination key and the signature with
@@ -1012,6 +1013,36 @@ void
 TALER_denom_sig_free (struct TALER_DenominationSignature *denom_sig);
 
 
+/**
+ * Function for CS signatures to derive the secret r_0 and r_1
+ *
+ * @param nonce withdraw nonce from a client
+ * @param denom_priv denomination privkey as long-term secret
+ * @param r the resulting r_0 and r_1
+ * @return enum GNUNET_GenericReturnValue, returns SYSERR when denom key has 
wrong type
+ */
+enum GNUNET_GenericReturnValue
+TALER_denom_cs_derive_r_secret (const struct TALER_WithdrawNonce *nonce,
+                                const struct
+                                TALER_DenominationPrivateKey *denom_priv,
+                                struct TALER_DenominationCsPrivateR *r);
+
+/**
+ * @brief Function for CS signatures to derive public R_0 and R_1
+ *
+ * @param nonce withdraw nonce from a client
+ * @param denom_priv denomination privkey as long-term secret
+ * @param r_pub the resulting R_0 and R_1
+ * @return enum GNUNET_GenericReturnValue
+ */
+
+enum GNUNET_GenericReturnValue
+TALER_denom_cs_derive_r_public (const struct TALER_WithdrawNonce *nonce,
+                                const struct
+                                TALER_DenominationPrivateKey *denom_priv,
+                                struct TALER_DenominationCsPublicR *r_pub);
+
+
 /**
  * Blind coin for blind signing with @a dk using blinding secret @a coin_bks.
  *
diff --git a/src/util/crypto.c b/src/util/crypto.c
index 40c69b54..1ef0388d 100644
--- a/src/util/crypto.c
+++ b/src/util/crypto.c
@@ -167,8 +167,8 @@ TALER_planchet_setup_refresh (const struct 
TALER_TransferSecretP *secret_seed,
 
 
 void
-cs_blinding_seed_derive (const void *secret,
-                         size_t secret_len,
+cs_blinding_seed_derive (const struct
+                         TALER_CoinSpendPrivateKeyP *coin_priv,
                          const struct GNUNET_CRYPTO_CsRPublic r_pub[2],
                          struct GNUNET_CRYPTO_CsNonce *blind_seed)
 {
@@ -179,8 +179,8 @@ cs_blinding_seed_derive (const void *secret,
                                      GCRY_MD_SHA256,
                                      "bseed",
                                      strlen ("bseed"),
-                                     secret,
-                                     secret_len,
+                                     coin_priv,
+                                     sizeof(*coin_priv),
                                      r_pub,
                                      sizeof(struct GNUNET_CRYPTO_CsRPublic) * 
2,
                                      NULL,
@@ -227,11 +227,13 @@ TALER_blinding_secret_create (union 
TALER_DenominationBlindingKeyP *bs,
     return;
   case TALER_DENOMINATION_CS:
     {
-      struct TALER_PlanchetDeriveCsBlindingSecrets *params;
-      params = va_arg (ap, struct TALER_PlanchetDeriveCsBlindingSecrets *);
-      cs_blinding_seed_derive (params->secret,
-                               params->secret_len,
-                               params->r_pub,
+      struct TALER_CoinSpendPrivateKeyP *coin_priv;
+      struct TALER_DenominationCsPublicR *r_pub;
+      coin_priv = va_arg (ap, struct TALER_CoinSpendPrivateKeyP *);
+      r_pub = va_arg (ap, struct TALER_DenominationCsPublicR *);
+
+      cs_blinding_seed_derive (coin_priv,
+                               r_pub->r_pub,
                                &bs->nonce);
       return;
     }
diff --git a/src/util/denom.c b/src/util/denom.c
index 6ff92e89..6b587026 100644
--- a/src/util/denom.c
+++ b/src/util/denom.c
@@ -81,6 +81,47 @@ TALER_denom_priv_create (struct TALER_DenominationPrivateKey 
*denom_priv,
 }
 
 
+enum GNUNET_GenericReturnValue
+TALER_denom_cs_derive_r_secret (const struct TALER_WithdrawNonce *nonce,
+                                const struct
+                                TALER_DenominationPrivateKey *denom_priv,
+                                struct TALER_DenominationCsPrivateR *r)
+{
+  if (denom_priv->cipher != TALER_DENOMINATION_CS)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+
+  GNUNET_CRYPTO_cs_r_derive (&nonce->nonce,
+                             &denom_priv->details.cs_private_key,
+                             r->r);
+  return GNUNET_OK;
+}
+
+
+enum GNUNET_GenericReturnValue
+TALER_denom_cs_derive_r_public (const struct TALER_WithdrawNonce *nonce,
+                                const struct
+                                TALER_DenominationPrivateKey *denom_priv,
+                                struct TALER_DenominationCsPublicR *r_pub)
+{
+  if (denom_priv->cipher != TALER_DENOMINATION_CS)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+
+  struct GNUNET_CRYPTO_CsRSecret r[2];
+  GNUNET_CRYPTO_cs_r_derive (&nonce->nonce,
+                             &denom_priv->details.cs_private_key,
+                             r);
+  GNUNET_CRYPTO_cs_r_get_public (&r[0], &r_pub->r_pub[0]);
+  GNUNET_CRYPTO_cs_r_get_public (&r[1], &r_pub->r_pub[1]);
+  return GNUNET_OK;
+}
+
+
 enum GNUNET_GenericReturnValue
 TALER_denom_sign_blinded (struct TALER_BlindedDenominationSignature *denom_sig,
                           const struct TALER_DenominationPrivateKey 
*denom_priv,
diff --git a/src/util/test_crypto.c b/src/util/test_crypto.c
index a91536bf..2fe70cda 100644
--- a/src/util/test_crypto.c
+++ b/src/util/test_crypto.c
@@ -147,6 +147,8 @@ test_planchets_cs (void)
   struct TALER_PlanchetDetail pd;
   struct TALER_CoinPubHash c_hash;
   struct TALER_WithdrawNonce nonce;
+  struct TALER_DenominationCsPublicR r_pub;
+  // struct TALER_DenominationCsPrivateR priv_r;
   // struct TALER_BlindedDenominationSignature blind_sig;
   // struct TALER_FreshCoin coin;
   // struct TALER_PlanchetDeriveCsBlindingSecrets seed;
@@ -156,14 +158,18 @@ test_planchets_cs (void)
                                           &dk_pub,
                                           TALER_DENOMINATION_CS));
 
-  // seed.secret = "test secret";
-  // seed.secret_len = strlen ("test secret");
-
   TALER_planchet_setup_random (&ps, TALER_DENOMINATION_CS);
   TALER_cs_withdraw_nonce_derive (&ps.coin_priv, &nonce);
-
-  // NEXT: Implement to create withdraw nonce
-  // Implement to get R_0 and R_1
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_denom_cs_derive_r_public (&nonce,
+                                                 &dk_priv,
+                                                 &r_pub));
+  TALER_blinding_secret_create (&ps.blinding_key,
+                                TALER_DENOMINATION_CS,
+                                &ps.coin_priv,
+                                &r_pub);
+
+  // NEXT:
   // Implement to genrate b-seed from it and calculate c then§
 
   // GNUNET_assert (GNUNET_OK ==

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