blow up k on M+1st price auctions

1 files changed, 20 insertions, 3 deletions

diff --git a/brandt.c b/brandt.c
index d466fff..0c7b40e 100644
--- a/brandt.c
+++ b/brandt.c
@@ -55,17 +55,26 @@ BRANDT_bidder_start (struct BRANDT_Auction *auction,
                      uint16_t              i,
                      uint16_t              n)
 {
-        GNUNET_assert (auction && n > 0 && i < n);
-        auction->n = n;
-        auction->i = i;
         enum auction_type atype;
         enum outcome_type outcome;
         unsigned char     *buf;
         size_t            buflen;
 
+        GNUNET_assert (auction && n > 0 && i < n);
+        auction->n = n;
+        auction->i = i;
+
         atype = auction->m > 0 ? auction_mPlusFirstPrice : auction_firstPrice;
         outcome = auction->outcome_public ? outcome_public : outcome_private;
 
+        /* On M+1st price auctions we multiply the amount of prizes by the amount of
+         * bidders and resctrict each bidder to his own distinct subset of the
+         * prices. This is done for tie breaking. An additional proof is used in the
+         * encrypt_bid round to show that the bidder has chosen a valid bid and the
+         * outcome callback will remap the result to the original k price values. */
+        if (auction_mPlusFirstPrice == atype)
+                auction->k *= n;
+
         if (handler_prep[atype][outcome][msg_init])
                 handler_prep[atype][outcome][msg_init] (auction);
 
@@ -102,6 +111,14 @@ seller_start (void *arg)
         atype = ad->m > 0 ? auction_mPlusFirstPrice : auction_firstPrice;
         outcome = ad->outcome_public ? outcome_public : outcome_private;
 
+        /* On M+1st price auctions we multiply the amount of prizes by the amount of
+         * bidders and resctrict each bidder to his own distinct subset of the
+         * prices. This is done for tie breaking. An additional proof is used in the
+         * encrypt_bid round to show that the bidder has chosen a valid bid and the
+         * outcome callback will remap the result to the original k price values. */
+        if (auction_mPlusFirstPrice == atype)
+                ad->k *= ad->n;
+
         if (handler_prep[atype][outcome][msg_init])
                 handler_prep[atype][outcome][msg_init] (ad);
 }