finish/fix public first price auctions

1 files changed, 20 insertions, 7 deletions

diff --git a/crypto.c b/crypto.c
index 95e2297..63017a5 100644
--- a/crypto.c
+++ b/crypto.c
@@ -407,7 +407,9 @@ smc_free1 (gcry_mpi_point_t *dst, uint16_t size1)
 
 
 /**
- * smc_init1 creates a 1 dimensional array of curve points
+ * smc_init1 creates a 1 dimensional array of curve points. Make sure to
+ * initialize the values before using them, they are not automatically set to
+ * the zero point!
  *
  * @param[in] size1 size of the first dimension
  * @return a pointer to the array or NULL on error.
@@ -460,7 +462,9 @@ smc_free2 (gcry_mpi_point_t **dst, uint16_t size1, uint16_t size2)
 
 
 /**
- * smc_init2 creates a 2 dimensional array of curve points
+ * smc_init2 creates a 2 dimensional array of curve points. Make sure to
+ * initialize the values before using them, they are not automatically set to
+ * the zero point!
  *
  * @param[in] size1 size of the first dimension
  * @param[in] size2 size of the second dimension
@@ -525,7 +529,9 @@ smc_free3 (gcry_mpi_point_t ***dst,
 
 
 /**
- * smc_init3 creates a 3 dimensional array of curve points
+ * smc_init3 creates a 3 dimensional array of curve points. Make sure to
+ * initialize the values before using them, they are not automatically set to
+ * the zero point!
  *
  * @param[in] size1 size of the first dimension
  * @param[in] size2 size of the second dimension
@@ -884,8 +890,15 @@ fp_pub_compute_outcome (struct BRANDT_Auction *ad, size_t *buflen)
         brandt_assert (!ec_point_cmp (ec_zero, tlta1[ad->k - 1]));
         brandt_assert (!ec_point_cmp (ec_zero, tltb1[ad->k - 1]));
 
-        /* temporarily store the \sum_{i=1}^n2^{i-1}b_i in tmp1, since it is needed
-         * each time a gamma,delta pair is received from another bidder */
+        /* initialize tmp array with zeroes, since we are calculating a sum */
+        for (uint16_t j = 0; j < ad->k; j++)
+        {
+                ec_point_copy (ad->tmpa1[j], ec_zero);
+                ec_point_copy (ad->tmpb1[j], ec_zero);
+        }
+        /* store the \sum_{i=1}^n2^{i-1}b_i in tmp1 until outcome determination,
+         * since it is needed each time a gamma,delta pair is received from another
+         * bidder */
         for (uint16_t i = 0; i < ad->n; i++)
         {
                 for (uint16_t j = 0; j < ad->k; j++)
@@ -895,7 +908,7 @@ fp_pub_compute_outcome (struct BRANDT_Auction *ad, size_t *buflen)
                         gcry_mpi_ec_mul (tmp, coeff, ad->beta[i][j], ec_ctx);
                         gcry_mpi_ec_add (ad->tmpb1[j], ad->tmpb1[j], tmp, ec_ctx);
                 }
-                gcry_mpi_mul_ui (coeff, coeff, 2);
+                gcry_mpi_lshift (coeff, coeff, 1);
         }
 
         for (uint16_t j = 0; j < ad->k; j++)
@@ -1033,7 +1046,7 @@ fp_pub_decrypt_outcome (struct BRANDT_Auction *ad, size_t *buflen)
                 phi = (struct ec_mpi *)cur;
                 proof2 = (struct proof_2dle *)(cur + sizeof (*phi));
 
-                smc_sum (tmp, &ad->delta2[0][j], ad->n, ad->n * ad->k);
+                smc_sum (tmp, &ad->delta2[0][j], ad->n, ad->k);
 
                 /* copy still encrypted outcome to all other bidder layers so they
                  * don't have to be recomputed to check the ZK proof_2dle's from