diff options
| -rw-r--r-- | gp-scripts/m+1stPrice | 91 | ||||
| -rw-r--r-- | smc.c | 14 |
2 files changed, 99 insertions, 6 deletions
diff --git a/gp-scripts/m+1stPrice b/gp-scripts/m+1stPrice new file mode 100644 index 0000000..8407e96 --- /dev/null +++ b/gp-scripts/m+1stPrice @@ -0,0 +1,91 @@ +\\ From: "Fully private auctions in a constant number of rounds" (2003) by Felix Brandt pages 9-10 + + +\\\\\\\\\\\\ +\\ Adapt the following values to your needs +\\\\\\\\\\\\ + +\\ amount of bidders +n = 2^3 +\\ amount of possible prices +k = 2^7 +\\ 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(4*n*k) + +\\\\\\\\\\\\ +\\ SETUP +\\\\\\\\\\\\ + +\\ p not needed? wat? +\\p = 47 + +\\ get generator / primitive element for Z_q +var = 'x \\ copy pasta from internet +pe=ffgen(minpoly(ffprimroot(ffgen(ffinit(q,1))),var),var) \\ get primitive element +1/(fforder(pe) == q-1) \\ error out, if ord(pe) is wrong +g = Mod(eval(Str(pe)), q) \\ 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 = vector(n,i,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 +Gamma = vector(n,a,matrix(n,k,i,j, ( prod(h=1,n,prod(d=j+1,k,alpha[h,d])) * prod(d=1,j-1,alpha[i,d]) * prod(h=1,i-1,alpha[h,j]) )^m[a][i,j] )) +Delta = vector(n,a,matrix(n,k,i,j, ( prod(h=1,n,prod(d=j+1,k, beta[h,d])) * prod(d=1,j-1, beta[i,d]) * prod(h=1,i-1, beta[h,j]) )^m[a][i,j] )) + +\\\\\\\\\\\\ +\\ ROUND3 +\\\\\\\\\\\\ + +\\ multiplicative shares (decryption) +\\ first index level = owning agent id (multiplicative share) +\\ second index level = agent id, price id +Phi = vector(n,a,matrix(n,k,i,j, prod(h=1,n,Delta[h][i,j])^x[a] )) + +\\\\\\\\\\\\ +\\ EPILOG +\\\\\\\\\\\\ + +\\ winner matrix +v = matrix(n,k,a,j, prod(i=1,n,Gamma[i][a,j]) / prod(i=1,n,Phi[i][a,j]) ) + +vi = lift(v) + +print("bids are: ", bid) +for(X=1,n, if(vecmin(vi[X,])==1, print("And the winner is ", X) )) @@ -24,7 +24,7 @@ #include <pari/pari.h> GEN -smc_hextodec (char *s) /* int */ +smc_hextodec (const char *s) /* int */ { size_t i; char c; @@ -46,7 +46,7 @@ smc_hextodec (char *s) /* int */ void -smc_genbid (AuctionData *ad, uint16_t bid) +smc_genbid (struct AuctionData *ad, uint16_t bid) { uint16_t j; pari_sp ltop = avma; @@ -59,8 +59,9 @@ smc_genbid (AuctionData *ad, uint16_t bid) ad->b = gerepilecopy (ltop, ret); } + void -smc_genalpha (AuctionData *ad) +smc_genalpha (struct AuctionData *ad) { uint16_t j; pari_sp ltop = avma; @@ -70,11 +71,12 @@ smc_genalpha (AuctionData *ad) { gel (ret, j) = gmul (gel (ad->b, j), gpowgi (ad->y, gel (ad->r, j))); } - ab->alpha = gerepilecopy (ltop, ret); + ad->alpha = gerepilecopy (ltop, ret); } + void -smc_genbeta (AuctionData *ad) +smc_genbeta (struct AuctionData *ad) { uint16_t j; pari_sp ltop = avma; @@ -84,6 +86,6 @@ smc_genbeta (AuctionData *ad) { gel (ret, j) = gpowgi (ad->g, gel (ad->r, j)); } - ab->beta = gerepilecopy (ltop, ret); + ad->beta = gerepilecopy (ltop, ret); } |