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-rw-r--r--Makefile.am1
-rw-r--r--brandt.c20
-rw-r--r--crypto.h30
-rw-r--r--gp-scripts/mp_pub104
-rw-r--r--mp_pub.c526
-rw-r--r--test_brandt.c28
6 files changed, 699 insertions, 10 deletions
diff --git a/Makefile.am b/Makefile.am
index e0b6356..9b80791 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -10,6 +10,7 @@ libbrandt_la_SOURCES = \
fp_priv.c \
fp_pub.c \
mp_priv.c \
+ mp_pub.c \
util.c
libbrandt_la_LIBADD = \
diff --git a/brandt.c b/brandt.c
index a05731d..ce41541 100644
--- a/brandt.c
+++ b/brandt.c
@@ -68,7 +68,7 @@ BRANDT_bidder_start (struct BRANDT_Auction *auction,
outcome = auction->outcome_public ? outcome_public : outcome_private;
if (auction_mPlusFirstPrice == atype && n <= auction->m)
- { /* fewer bidders than items to sell. every bidder won with lowest price */
+ { /* fewer bidders than items to sell. every bidder won with lowest price */
struct BRANDT_Result *res;
if (auction->outcome_public)
{
@@ -138,7 +138,8 @@ seller_start (void *arg)
}
else if (ad->n <= ad->m)
{
- struct BRANDT_Result *res = GNUNET_new_array (ad->n, struct BRANDT_Result);
+ struct BRANDT_Result *res = GNUNET_new_array (ad->n,
+ struct BRANDT_Result);
weprintf ("less bidders than needed, selling for lowest price");
for (uint16_t i = 0; i < ad->n; i++)
@@ -346,14 +347,23 @@ BRANDT_destroy (struct BRANDT_Auction *auction)
smc_free2 (auction->alpha, auction->n, auction->k);
smc_free2 (auction->beta, auction->n, auction->k);
smc_free2 (auction->gamma2, auction->n, auction->k);
- smc_free3 (auction->gamma3, auction->n, auction->n, auction->k);
smc_free2 (auction->delta2, auction->n, auction->k);
- smc_free3 (auction->delta3, auction->n, auction->n, auction->k);
smc_free2 (auction->phi2, auction->n, auction->k);
- smc_free3 (auction->phi3, auction->n, auction->n, auction->k);
free (auction->phiproofs3);
smc_free1 (auction->tmpa1, auction->k);
smc_free1 (auction->tmpb1, auction->k);
+ if (auction->m > 0 && auction->outcome_public)
+ {
+ smc_free3 (auction->gamma3, auction->n, 2, auction->k);
+ smc_free3 (auction->delta3, auction->n, 2, auction->k);
+ smc_free3 (auction->phi3, auction->n, 2, auction->k);
+ }
+ else
+ {
+ smc_free3 (auction->gamma3, auction->n, auction->n, auction->k);
+ smc_free3 (auction->delta3, auction->n, auction->n, auction->k);
+ smc_free3 (auction->phi3, auction->n, auction->n, auction->k);
+ }
}
diff --git a/crypto.h b/crypto.h
index 4c06b4a..8291bc2 100644
--- a/crypto.h
+++ b/crypto.h
@@ -188,6 +188,26 @@ struct BRANDT_Result *mp_priv_determine_outcome (struct BRANDT_Auction *ad,
uint16_t *len);
+void mp_pub_prep_outcome (struct BRANDT_Auction *ad);
+unsigned char *mp_pub_compute_outcome (struct BRANDT_Auction *ad,
+ size_t *buflen);
+int mp_pub_recv_outcome (struct BRANDT_Auction *ad,
+ const unsigned char *buf,
+ size_t buflen,
+ uint16_t sender);
+
+void mp_pub_prep_decryption (struct BRANDT_Auction *ad);
+unsigned char *mp_pub_decrypt_outcome (struct BRANDT_Auction *ad,
+ size_t *buflen);
+int mp_pub_recv_decryption (struct BRANDT_Auction *ad,
+ const unsigned char *buf,
+ size_t buflen,
+ uint16_t sender);
+
+struct BRANDT_Result *mp_pub_determine_outcome (struct BRANDT_Auction *ad,
+ uint16_t *len);
+
+
/* --- Round dictionaries --- */
typedef void
@@ -245,6 +265,8 @@ static const RoundPrep handler_prep[auction_last][outcome_last][msg_last] = {
[outcome_public] = {
[msg_init] = &smc_prep_keyshare,
[msg_bid] = &smc_prep_bid,
+ [msg_outcome] = &mp_pub_prep_outcome,
+ [msg_decrypt] = &mp_pub_prep_decryption,
},
},
};
@@ -285,6 +307,8 @@ static const MsgIn handler_in[auction_last][outcome_last][msg_last] = {
[outcome_public] = {
[msg_init] = &smc_recv_keyshare,
[msg_bid] = &smc_recv_encrypted_bid,
+ [msg_outcome] = &mp_pub_recv_outcome,
+ [msg_decrypt] = &mp_pub_recv_decryption,
},
},
};
@@ -326,6 +350,8 @@ static const MsgOut handler_out[auction_last][outcome_last][msg_last] = {
[outcome_public] = {
[msg_init] = &smc_gen_keyshare,
[msg_bid] = &smc_encrypt_bid,
+ [msg_outcome] = &mp_pub_compute_outcome,
+ [msg_decrypt] = &mp_pub_decrypt_outcome,
},
},
};
@@ -342,13 +368,13 @@ static const MsgOut handler_out[auction_last][outcome_last][msg_last] = {
* of 0 means a private outcome, while a value of 1 means public outcome.
*/
static const Result handler_res[auction_last][outcome_last] = {
- [auction_firstPrice] = {
+ [auction_firstPrice] = {
[outcome_private] = &fp_priv_determine_outcome,
[outcome_public] = &fp_pub_determine_outcome,
},
[auction_mPlusFirstPrice] = {
[outcome_private] = &mp_priv_determine_outcome,
-// [outcome_public] = ,
+ [outcome_public] = &mp_pub_determine_outcome,
},
};
diff --git a/gp-scripts/mp_pub b/gp-scripts/mp_pub
new file mode 100644
index 0000000..9b49c13
--- /dev/null
+++ b/gp-scripts/mp_pub
@@ -0,0 +1,104 @@
+\\ From: "Fully private auctions in a constant number of rounds" (2003) by Felix Brandt pages 9-10
+
+
+\\\\\\\\\\\\
+\\ Adapt the following values to your needs
+\\\\\\\\\\\\
+
+\\ auction parameter
+M = 1
+\\ amount of bidders
+n = 2^2
+\\ amount of possible prices
+k = 2^4
+\\ randomize bids (change to something static, if you like)
+bid = vector(n,i,random(k)+1)
+\\bid = vector(n,i,n-i+1) \\ first bidder wins
+\\bid = vector(n,i,i) \\ last bidder wins
+\\bid = vector(n,i,(i+1)%2) \\ second bidder wins (with ties)
+
+\\ prime finite field setup (result may be ambiguous if your prime is too small, 4*n*k seems to work fine)
+\\q = prime(2^12)
+\\ 512bit prime:
+q = 12513167897862218633350152063959653109080007724899931588313481862015596111526299656550478091592311160908219544364381660940520774223634480285451547911456579
+\\ 2048bit prime:
+\\q = 31905233907400964621684499856844075173802000556075101303613351426740101897961025481077892281365444367883091980681462491724119317344478120131982416132058173572772607966572720945691237876256074322291459510766147107539260048324345382562673904236506104922357079761457605045674628331006193183908801308817507027556440703972646885207099302085383887085776295396030033300833460743425162726394704256227108175491673135830378272029374848904772902525385997099641162537271298634032011458617811670193865244028195169383991286227040469186123958053863978710424421008752927011390777187889943940479064193231486057910586526439884046593027
+\\ 3072bit prime:
+\\q = 5175054779340588353586849786144680366505563673837334790820581054294754700842534366479020240016540005621125885927641963390708863183739793208880756653713659686139600715884857385144475261507869935694699816011948585170171332029002674283854825650901258017026965486602158722052719421343475066067509485302858041368266332080773331946039572497794442067057597327877030322029413318847025776818839927761556478107499002213648377029201340152459685610920194363099878398871001275336711869213616313858200583491913270052111910410231060407633125816386053759634073500319223989240814564691163285769745840521560940666058800931070258886096469889796899266014106833050284032035948051974659796051419431527095503586817863043771919051402039741075037010264761045992285666560487072740505566408086913711094879155498223636912657852688296081316652278801546924079650897913388978423388839346058027184069633227966507908979049369500450630036982661231208087459099
+g = Mod(2, q)
+
+\\ get generator / primitive element for G_q
+\\var = 'x \\ copy pasta from internet
+\\pe=ffgen(minpoly(ffprimroot(ffgen(ffinit(p,1))),var),var) \\ get primitive element
+\\1/(fforder(pe) == p-1) \\ error out, if ord(pe) is wrong
+\\g = Mod(eval(Str(pe))^2, p) \\ dirty hack to convert t_FFELEM to t_INT
+
+\\\\\\\\\\\\
+\\ PROLOG
+\\\\\\\\\\\\
+
+\\ private keys of agents
+x = vector(n,i,random(q))
+\\ public keyshares of agents
+yshares = vector(n,i,g^x[i])
+\\ shared public key
+y = prod(X=1,n,yshares[X])
+
+\\ first index level = owning agent id (additive share)
+\\ second index level = agent id, price id
+m = matrix(n,k,a,b,random(q))
+
+\\ index = owning agent id, price id
+r = matrix(n,k,i,j,random(q))
+\\ bid matrix
+b = matrix(n,k,i,j,g^(bid[i]==j))
+
+\\\\\\\\\\\\
+\\ ROUND1
+\\\\\\\\\\\\
+
+\\ encrypted bids
+alpha = matrix(n,k,i,j, b[i,j]*y^r[i,j])
+beta = matrix(n,k,i,j, g^r[i,j])
+
+\\\\\\\\\\\\
+\\ ROUND2
+\\\\\\\\\\\\
+
+\\ multiplicative shares
+\\ first index level = owning agent id (multiplicative share)
+\\ second index level = agent id, price id
+GammaPrice = matrix(n,k,a,j, ( prod(h=1,n,prod(d=j,k,alpha[h,d]) * prod(d=j+1,k,alpha[h,d])) / g^(2*M+1) )^(m[a,j]) )
+DeltaPrice = matrix(n,k,a,j, ( prod(h=1,n,prod(d=j,k, beta[h,d]) * prod(d=j+1,k, beta[h,d])) )^(m[a,j]) )
+GammaWinner = matrix(n,k,a,j, ( GammaPrice[a,j] * prod(h=1,n,prod(d=j+1,k,alpha[h,d]^(2^(h-1)))) ))
+DeltaWinner = matrix(n,k,a,j, ( DeltaPrice[a,j] * prod(h=1,n,prod(d=j+1,k, beta[h,d]^(2^(h-1)))) ))
+
+\\\\\\\\\\\\
+\\ ROUND3
+\\\\\\\\\\\\
+
+\\ multiplicative shares (decryption)
+\\ first index level = owning agent id (multiplicative share)
+\\ second index level = agent id, price id
+PhiPrice = matrix(n,k,a,j, prod(h=1,n,DeltaPrice[h,j])^x[a] )
+PhiWinner = matrix(n,k,a,j, prod(h=1,n,DeltaWinner[h,j])^x[a] )
+
+\\\\\\\\\\\\
+\\ EPILOG
+\\\\\\\\\\\\
+
+\\ winner matrix
+vPrice = lift(vector(k,j, prod(i=1,n,GammaPrice[i,j]) / prod(i=1,n,PhiPrice[i,j]) ))
+vWinner = vector(k,j, prod(i=1,n,GammaWinner[i,j]) / prod(i=1,n,PhiWinner[i,j]) )
+
+print("bids are: ", bid)
+
+price = -1
+for(j=1,k, if(vPrice[j]==1, price=j))
+
+winners = vector(i=1,M,-1)
+winp = binary(znlog(vWinner[price],g)/n)
+cur = 1;
+for(i=1,length(winp), if(winp[length(winp)-i+1]==1,winners[cur]=i;cur=cur+1))
+print("Winners are ", winners)
+print("And the price is ", price)
diff --git a/mp_pub.c b/mp_pub.c
new file mode 100644
index 0000000..7c2a373
--- /dev/null
+++ b/mp_pub.c
@@ -0,0 +1,526 @@
+/* This file is part of libbrandt.
+ * Copyright (C) 2016 GNUnet e.V.
+ *
+ * libbrandt 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
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * libbrandt is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * libbrandt. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file mp_pub.c
+ * @brief Implementation of the m+1st price public outcome algorithm.
+ * @author Markus Teich
+ */
+
+#include "platform.h"
+
+#include <gcrypt.h>
+
+#include "crypto.h"
+#include "internals.h"
+#include "util.h"
+
+
+void
+mp_pub_prep_outcome (struct BRANDT_Auction *ad)
+{
+ gcry_mpi_t factor = gcry_mpi_new (256);
+ gcry_mpi_point_t subtr = gcry_mpi_point_new (0);
+ gcry_mpi_point_t tmpa = gcry_mpi_point_new (0);
+ gcry_mpi_point_t tmpb = gcry_mpi_point_new (0);
+ gcry_mpi_point_t *tlta1;
+ gcry_mpi_point_t *tltb1;
+ gcry_mpi_point_t **tlta2;
+ gcry_mpi_point_t **tltb2;
+ gcry_mpi_point_t **tlta3;
+ gcry_mpi_point_t **tltb3;
+
+ ad->gamma3 = smc_init3 (ad->n, 2, ad->k);
+ brandt_assert (ad->gamma3);
+
+ ad->delta3 = smc_init3 (ad->n, 2, ad->k);
+ brandt_assert (ad->delta3);
+
+ /* create temporary lookup tables with partial sums */
+ tlta1 = smc_init1 (ad->k);
+ tltb1 = smc_init1 (ad->k);
+ tlta2 = smc_init2 (ad->n, ad->k);
+ tltb2 = smc_init2 (ad->n, ad->k);
+ tlta3 = smc_init2 (ad->n, ad->k);
+ tltb3 = smc_init2 (ad->n, ad->k);
+
+ /* temporary lookup table for first summand (building ladder of bids) */
+ for (uint16_t i = 0; i < ad->n; i++)
+ {
+ smc_sums_partial (tlta3[i], ad->alpha[i], ad->k, 1, 1);
+ smc_sums_partial (tltb3[i], ad->beta[i], ad->k, 1, 1);
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ gcry_mpi_ec_sub (tlta2[i][j],
+ tlta3[i][ad->k - 1],
+ tlta3[i][j],
+ ec_ctx);
+ gcry_mpi_ec_sub (tltb2[i][j],
+ tltb3[i][ad->k - 1],
+ tltb3[i][j],
+ ec_ctx);
+ }
+ brandt_assert (!ec_point_cmp (ec_zero, tlta2[i][ad->k - 1]));
+ brandt_assert (!ec_point_cmp (ec_zero, tltb2[i][ad->k - 1]));
+ }
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ /* 2L - 2I */
+ smc_sum (tmpa, &tlta2[0][j], ad->n, ad->k);
+ smc_sum (tmpb, &tltb2[0][j], ad->n, ad->k);
+ gcry_mpi_ec_mul (tlta1[j], GCRYMPI_CONST_TWO, tmpa, ec_ctx);
+ gcry_mpi_ec_mul (tltb1[j], GCRYMPI_CONST_TWO, tmpb, ec_ctx);
+
+ /* I */
+ smc_sum (tmpa, &ad->alpha[0][j], ad->n, ad->k);
+ smc_sum (tmpb, &ad->beta[0][j], ad->n, ad->k);
+
+ /* 2L - 2I + I = 2L - I */
+ gcry_mpi_ec_add (tlta1[j], tlta1[j], tmpa, ec_ctx);
+ gcry_mpi_ec_add (tltb1[j], tltb1[j], tmpb, ec_ctx);
+ }
+ brandt_assert (!ec_point_cmp (tmpa, tlta1[ad->k - 1]));
+ brandt_assert (!ec_point_cmp (tmpb, tltb1[ad->k - 1]));
+
+ /* compute subtrahend: (2M+1)G */
+ gcry_mpi_set_ui (factor, ad->m);
+ gcry_mpi_lshift (factor, factor, 1);
+ gcry_mpi_add_ui (factor, factor, 1);
+ gcry_mpi_ec_mul (subtr, factor, ec_gen, ec_ctx);
+
+ /* compute gamma and delta for price determination */
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ /* compute inner gamma */
+ gcry_mpi_ec_sub (tmpa, tlta1[j], subtr, ec_ctx);
+
+ /* inner delta */
+ ec_point_copy (tmpb, tltb1[j]);
+
+ /* copy unmasked outcome to all other bidder layers so they don't
+ * have to be recomputed to check the ZK proof_2dle's from other
+ * bidders when receiving their outcome messages */
+ for (uint16_t a = 0; a < ad->n; a++)
+ {
+ ec_point_copy (ad->gamma3[a][0][j], tmpa);
+ ec_point_copy (ad->delta3[a][0][j], tmpb);
+ }
+ }
+
+ /* gamma and delta for winner determination: compute
+ * @f$\sum_{h=1}^n\sum_{d=j+1}^k2^{h-1}b_h@f and store it in every bidders gamma and
+ * delta, 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++)
+ {
+ /* initialize with zeroes, since we are calculating a sum */
+ ec_point_copy (ad->gamma3[i][1][j], ec_zero);
+ ec_point_copy (ad->delta3[i][1][j], ec_zero);
+ }
+ }
+ gcry_mpi_set_ui (factor, 1);
+ for (uint16_t h = 0; h < ad->n; h++)
+ {
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ for (uint16_t d = j + 1; d < ad->k; d++)
+ {
+ gcry_mpi_ec_mul (tmpa, factor, ad->alpha[h][d], ec_ctx);
+ gcry_mpi_ec_add (ad->gamma3[0][1][j],
+ ad->gamma3[0][1][j],
+ tmpa,
+ ec_ctx);
+ gcry_mpi_ec_mul (tmpb, factor, ad->beta[h][d], ec_ctx);
+ gcry_mpi_ec_add (ad->delta3[0][1][j],
+ ad->delta3[0][1][j],
+ tmpb,
+ ec_ctx);
+ }
+ }
+ gcry_mpi_lshift (factor, factor, 1);
+ }
+ /* copy component to all bidders so they don't have to be recomputed */
+ for (uint16_t a = 1; a < ad->n; a++)
+ {
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ ec_point_copy (ad->gamma3[a][1][j], ad->gamma3[0][1][j]);
+ ec_point_copy (ad->delta3[a][1][j], ad->delta3[0][1][j]);
+ }
+ }
+
+ gcry_mpi_release (factor);
+ gcry_mpi_point_release (subtr);
+ gcry_mpi_point_release (tmpa);
+ gcry_mpi_point_release (tmpb);
+ smc_free1 (tlta1, ad->k);
+ smc_free1 (tltb1, ad->k);
+ smc_free2 (tlta2, ad->n, ad->k);
+ smc_free2 (tltb2, ad->n, ad->k);
+ smc_free2 (tlta3, ad->n, ad->k);
+ smc_free2 (tltb3, ad->n, ad->k);
+}
+
+
+/**
+ * mp_pub_compute_outcome computes encrypted outcome shares and packs them into
+ * a message buffer together with proofs of correctnes.
+ *
+ * @param[in] ad Pointer to the BRANDT_Auction struct to operate on
+ * @param[out] buflen Size of the returned message buffer in bytes
+ * @return A buffer containing the encrypted outcome vectors
+ * which needs to be broadcast
+ */
+unsigned char *
+mp_pub_compute_outcome (struct BRANDT_Auction *ad, size_t *buflen)
+{
+ unsigned char *ret;
+ unsigned char *cur;
+ struct msg_head *head;
+ gcry_mpi_point_t tmpa = gcry_mpi_point_new (0);
+ gcry_mpi_point_t tmpb = gcry_mpi_point_new (0);
+ struct ec_mpi *gamma;
+ struct ec_mpi *delta;
+ struct proof_2dle *proof2;
+
+ brandt_assert (ad && buflen);
+
+ *buflen = (sizeof (*head) + /* msg header */
+ ad->k * /* k * (gamma, delta, proof2) */
+ (sizeof (*gamma) + sizeof (*delta) + sizeof (*proof2)));
+ ret = GNUNET_new_array (*buflen, unsigned char);
+
+ head = (struct msg_head *)ret;
+ head->prot_version = htonl (0);
+ head->msg_type = htonl (msg_outcome);
+ cur = ret + sizeof (*head);
+
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ gamma = (struct ec_mpi *)cur;
+ delta = &((struct ec_mpi *)cur)[1];
+ proof2 = (struct proof_2dle *)(cur + 2 * sizeof (struct ec_mpi));
+
+ /* only send the price determination gamma,delta pair, since the winner
+ * determination pair can and will be computed by the receiver */
+ ec_point_copy (tmpa, ad->gamma3[ad->i][0][j]);
+ ec_point_copy (tmpb, ad->delta3[ad->i][0][j]);
+
+ /* apply random masking for losing bidders */
+ smc_zkp_2dle (ad->gamma3[ad->i][0][j],
+ ad->delta3[ad->i][0][j],
+ tmpa,
+ tmpb,
+ NULL,
+ proof2);
+
+ ec_point_serialize (gamma, ad->gamma3[ad->i][0][j]);
+ ec_point_serialize (delta, ad->delta3[ad->i][0][j]);
+
+ /* compute own winner determination gamma,delta pair */
+ gcry_mpi_ec_add (ad->gamma3[ad->i][1][j],
+ ad->gamma3[ad->i][0][j],
+ ad->gamma3[ad->i][1][j],
+ ec_ctx);
+ gcry_mpi_ec_add (ad->delta3[ad->i][1][j],
+ ad->delta3[ad->i][0][j],
+ ad->delta3[ad->i][1][j],
+ ec_ctx);
+
+ cur += sizeof (*gamma) + sizeof (*delta) + sizeof (*proof2);
+ }
+
+ gcry_mpi_point_release (tmpa);
+ gcry_mpi_point_release (tmpb);
+ return ret;
+}
+
+
+int
+mp_pub_recv_outcome (struct BRANDT_Auction *ad,
+ const unsigned char *buf,
+ size_t buflen,
+ uint16_t sender)
+{
+ int ret = 0;
+ const unsigned char *cur = buf;
+ struct proof_2dle *proof2;
+ gcry_mpi_point_t gamma = gcry_mpi_point_new (0);
+ gcry_mpi_point_t delta = gcry_mpi_point_new (0);
+
+ brandt_assert (ad && buf);
+
+ if (buflen != (ad->k * (2 * sizeof (struct ec_mpi) + sizeof (*proof2))))
+ {
+ weprintf ("wrong size of received outcome");
+ goto quit;
+ }
+
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ ec_point_parse (gamma, (struct ec_mpi *)cur);
+ ec_point_parse (delta, &((struct ec_mpi *)cur)[1]);
+ proof2 = (struct proof_2dle *)(cur + 2 * sizeof (struct ec_mpi));
+ if (smc_zkp_2dle_check (gamma,
+ delta,
+ ad->gamma3[sender][0][j],
+ ad->delta3[sender][0][j],
+ proof2))
+ {
+ weprintf ("wrong zkp2 for gamma, delta received");
+ goto quit;
+ }
+ ec_point_copy (ad->gamma3[sender][0][j], gamma);
+ ec_point_copy (ad->delta3[sender][0][j], delta);
+
+ /* compute winner determination gamma,delta pair */
+ gcry_mpi_ec_add (ad->gamma3[sender][1][j],
+ ad->gamma3[sender][0][j],
+ ad->gamma3[sender][1][j],
+ ec_ctx);
+ gcry_mpi_ec_add (ad->delta3[sender][1][j],
+ ad->delta3[sender][0][j],
+ ad->delta3[sender][1][j],
+ ec_ctx);
+
+ cur += 2 * sizeof (struct ec_mpi) + sizeof (*proof2);
+ }
+
+ ret = 1;
+quit:
+ gcry_mpi_point_release (gamma);
+ gcry_mpi_point_release (delta);
+ return ret;
+}
+
+
+void
+mp_pub_prep_decryption (struct BRANDT_Auction *ad)
+{
+ gcry_mpi_point_t tmp_price = gcry_mpi_point_new (0);
+ gcry_mpi_point_t tmp_winner = gcry_mpi_point_new (0);
+
+ ad->phi3 = smc_init3 (ad->n, 2, ad->k);
+ brandt_assert (ad->phi3);
+
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ smc_sum (tmp_price, &ad->delta3[0][0][j], ad->n, 2 * ad->k);
+ smc_sum (tmp_winner, &ad->delta3[0][1][j], ad->n, 2 * 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
+ * other bidders when receiving their outcome decryption messages */
+ for (uint16_t a = 0; a < ad->n; a++)
+ {
+ ec_point_copy (ad->phi3[a][0][j], tmp_price);
+ ec_point_copy (ad->phi3[a][1][j], tmp_winner);
+ }
+ }
+
+ gcry_mpi_point_release (tmp_price);
+ gcry_mpi_point_release (tmp_winner);
+}
+
+
+/**
+ * mp_pub_decrypt_outcome decrypts part of the outcome and packs it into a
+ * message buffer together with proofs of correctnes.
+ *
+ * @param[in] ad Pointer to the BRANDT_Auction struct to operate on
+ * @param[out] buflen Size of the returned message buffer in bytes
+ * @return A buffer containing the own share of the decrypted outcome
+ * which needs to be broadcast
+ */
+unsigned char *
+mp_pub_decrypt_outcome (struct BRANDT_Auction *ad, size_t *buflen)
+{
+ unsigned char *ret;
+ unsigned char *cur;
+ gcry_mpi_point_t tmp = gcry_mpi_point_new (0);
+ struct msg_head *head;
+ struct ec_mpi *phi;
+ struct proof_2dle *proof2;
+
+ brandt_assert (ad && buflen);
+
+ *buflen = (sizeof (*head) + 2 * ad->k * (sizeof (*phi) + sizeof (*proof2)));
+ ret = GNUNET_new_array (*buflen, unsigned char);
+
+ head = (struct msg_head *)ret;
+ head->prot_version = htonl (0);
+ head->msg_type = htonl (msg_decrypt);
+ cur = ret + sizeof (*head);
+
+ /* decrypt price and winner components */
+ for (uint16_t comp = 0; comp < 2; comp++)
+ {
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ phi = (struct ec_mpi *)cur;
+ proof2 = (struct proof_2dle *)(cur + sizeof (*phi));
+
+ ec_point_copy (tmp, ad->phi3[ad->i][comp][j]);
+
+ /* decrypt outcome component and prove the correct key was used */
+ smc_zkp_2dle (ad->phi3[ad->i][comp][j],
+ NULL,
+ tmp,
+ ec_gen,
+ ad->x,
+ proof2);
+
+ ec_point_serialize (phi, ad->phi3[ad->i][comp][j]);
+
+ cur += sizeof (*phi) + sizeof (*proof2);
+ }
+ }
+
+ gcry_mpi_point_release (tmp);
+ return ret;
+}
+
+
+int
+mp_pub_recv_decryption (struct BRANDT_Auction *ad,
+ const unsigned char *buf,
+ size_t buflen,
+ uint16_t sender)
+{
+ int ret = 0;
+ const unsigned char *cur = buf;
+ struct proof_2dle *proof2;
+ gcry_mpi_point_t phi = gcry_mpi_point_new (0);
+
+ brandt_assert (ad && buf);
+
+ if (buflen != (2 * ad->k * (sizeof (struct ec_mpi) + sizeof (*proof2))))
+ {
+ weprintf ("wrong size of received outcome decryption");
+ goto quit;
+ }
+
+ /* handle received price and winner components */
+ for (uint16_t comp = 0; comp < 2; comp++)
+ {
+ for (uint16_t j = 0; j < ad->k; j++)
+ {
+ ec_point_parse (phi, (struct ec_mpi *)cur);
+ proof2 = (struct proof_2dle *)(cur + sizeof (struct ec_mpi));
+
+ if (smc_zkp_2dle_check (phi,
+ ad->y[sender],
+ ad->phi3[sender][comp][j],
+ ec_gen,
+ proof2))
+ {
+ weprintf ("wrong zkp2 for phi, y received");
+ goto quit;
+ }
+ ec_point_copy (ad->phi3[sender][comp][j], phi);
+ cur += sizeof (struct ec_mpi) + sizeof (*proof2);
+ }
+ }
+
+ ret = 1;
+quit:
+ gcry_mpi_point_release (phi);
+ return ret;
+}
+
+
+struct BRANDT_Result *
+mp_pub_determine_outcome (struct BRANDT_Auction *ad,
+ uint16_t *len)
+{
+ struct BRANDT_Result *ret;
+ int32_t price = -1;
+ uint16_t cur_winner = 0;
+ int dlogi = -1;
+ gcry_mpi_point_t sum_gamma = gcry_mpi_point_new (0);
+ gcry_mpi_point_t sum_phi = gcry_mpi_point_new (0);
+
+ brandt_assert (ad);
+
+ for (uint16_t j = ad->k - 1; j >= 0; j--)
+ {
+ smc_sum (sum_gamma, &ad->gamma3[0][0][j], ad->n, 2 * ad->k);
+ smc_sum (sum_phi, &ad->phi3[0][0][j], ad->n, 2 * ad->k);
+ gcry_mpi_ec_sub (sum_gamma, sum_gamma, sum_phi, ec_ctx);
+ /* first zero component determines the price */
+ if (!ec_point_cmp (sum_gamma, ec_zero))
+ {
+ price = j;
+ break;
+ }
+ }
+
+ if (-1 == price)
+ return NULL;
+
+ /* extract winners point for the winning price */
+ smc_sum (sum_gamma, &ad->gamma3[0][1][price], ad->n, 2 * ad->k);
+ smc_sum (sum_phi, &ad->phi3[0][1][price], ad->n, 2 * ad->k);
+ gcry_mpi_ec_sub (sum_gamma, sum_gamma, sum_phi, ec_ctx);
+
+ dlogi = GNUNET_CRYPTO_ecc_dlog (ec_dlogctx, sum_gamma);
+ brandt_assert (dlogi > 0);
+
+ /* all bidders participated with a multiplicative share */
+ dlogi /= ad->n;
+
+ price = price / ad->n;
+ ret = GNUNET_new_array (ad->m, struct BRANDT_Result);
+
+ /* can only support up to bits(dlogi) bidders */
+ brandt_assert (sizeof (int) * 8 > ad->n);
+ for (uint16_t i = 0; i < ad->n; i++)
+ {
+ /* a set bit determines a winner */
+ if (dlogi & (1 << i))
+ {
+ if (cur_winner >= ad->m)
+ {
+ weprintf ("too many winners detected");
+ GNUNET_free (ret);
+ ret = NULL;
+ goto quit;
+ }
+
+ ret[cur_winner].bidder = i;
+ ret[cur_winner].price = price;
+ ret[cur_winner].status = BRANDT_bidder_won;
+ cur_winner++;
+ }
+ }
+
+ if (cur_winner != ad->m)
+ {
+ weprintf ("too few winners detected");
+ GNUNET_free (ret);
+ ret = NULL;
+ goto quit;
+ }
+
+ if (len)
+ *len = ad->m;
+quit:
+ gcry_mpi_point_release (sum_gamma);
+ gcry_mpi_point_release (sum_phi);
+ return ret;
+}
diff --git a/test_brandt.c b/test_brandt.c
index 46ec90d..d18b17a 100644
--- a/test_brandt.c
+++ b/test_brandt.c
@@ -54,7 +54,7 @@ static struct testcase tcase;
static struct BRANDT_Result *
-expected_outcome (uint16_t i)
+expected_outcome (uint16_t i, uint16_t *rlen)
{
struct BRANDT_Result *ret = NULL;
int32_t highest_bidder = -1;
@@ -65,6 +65,8 @@ expected_outcome (uint16_t i)
uint16_t winners = MIN (tcase.m, tcase.n);
uint16_t cur_winner = 0;
+ *rlen = 0;
+
if (0 == tcase.n)
return NULL;
@@ -81,6 +83,7 @@ expected_outcome (uint16_t i)
ret->bidder = highest_bidder;
ret->price = highest_bid;
ret->status = BRANDT_bidder_won;
+ *rlen = 1;
return ret;
}
@@ -89,7 +92,7 @@ expected_outcome (uint16_t i)
{
if (tcase.outcome_public || i == tcase.n)
{
- ret = GNUNET_new_array (tcase.n, struct BRANDT_Result);
+ ret = GNUNET_new_array ((*rlen = tcase.n), struct BRANDT_Result);
for (uint16_t h = 0; h < tcase.n; h++)
{
ret[h].bidder = h;
@@ -103,6 +106,7 @@ expected_outcome (uint16_t i)
ret->bidder = i;
ret->price = 0;
ret->status = BRANDT_bidder_won;
+ *rlen = 1;
}
return ret;
}
@@ -154,6 +158,7 @@ expected_outcome (uint16_t i)
cur_winner++;
}
}
+ *rlen = cur_winner;
return ret;
}
@@ -250,7 +255,16 @@ cb_result (void *auction_closure,
uint16_t results_len)
{
uint16_t *s = (uint16_t *)auction_closure;
- struct BRANDT_Result *must = expected_outcome (*s);
+ uint16_t mustlen = -1;
+ struct BRANDT_Result *must = expected_outcome (*s, &mustlen);
+
+ if (mustlen != results_len)
+ {
+ weprintf ("expected result len is: %d", mustlen);
+ weprintf ("computed result len is: %d (by agent %d)", results_len, *s);
+ tcase.ret = 1;
+ goto quit;
+ }
if (0 == results_len)
{
@@ -281,6 +295,7 @@ cb_result (void *auction_closure,
tcase.ret = 1;
}
+quit:
tcase.result_called[*s] = 1;
if (must)
GNUNET_free (must);
@@ -406,17 +421,24 @@ main (int argc, char *argv[])
BRANDT_init (edc);
ret |= 0 ||
+ // zero bidders
test_auction (0, 2, NULL, 0, 0) ||
test_auction (0, 2, NULL, 0, 1) ||
test_auction (0, 2, NULL, 1, 0) ||
test_auction (0, 2, NULL, 2, 0) ||
+
+ // too few bidders => outcome is lowest possible price
test_auction (1, 2, (uint16_t[]) { 1 }, 1, 0) ||
test_auction (1, 2, (uint16_t[]) { 0 }, 2, 0) ||
test_auction (2, 2, (uint16_t[]) { 1, 0 }, 2, 0) ||
test_auction (2, 2, (uint16_t[]) { 1, 0 }, 1, 0) ||
test_auction (3, 2, (uint16_t[]) { 0, 0, 1 }, 2, 0) ||
+
+ // general checks of all four algorithms
test_auction (3, 2, (uint16_t[]) { 0, 1, 1 }, 0, 0) ||
test_auction (3, 2, (uint16_t[]) { 0, 1, 1 }, 0, 1) ||
+ test_auction (3, 2, (uint16_t[]) { 0, 1, 1 }, 2, 0) ||
+ test_auction (3, 2, (uint16_t[]) { 0, 1, 1 }, 2, 1) ||
0;
GNUNET_CRYPTO_ecc_dlog_release (edc);