AtHeartEngineer/PageSigner
1
0
Fork 0
mirror of https://github.com/tlsnotary/PageSigner.git synced 2026-01-09 14:48:07 -05:00
Code Issues Packages Projects Releases Wiki Activity

fix for very small request

Browse Source
This commit is contained in:
themighty1
2021-12-09 11:32:55 +03:00
parent fe6a75e41f
commit cdb21f3671
1 changed files with 20 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
core/twopc/TWOPC.js
View File

@@ -501,21 +501,26 @@ export class TWOPC {
}
// for those shares of powers which are not in powersOfH, we do not compute the shares of
// powers, but instead we compute the share of X*H
// e.g. if we need H^21*X and we have shares of H^19 and H^2, we compute it as follows:
// (H19_a + H19_b)(H2_a + H2_b)X == H19_aH2_aX + H19_aXH2_b + H19_bXH2_a + H19_bH2_bX
// powers, but instead we compute the share of X_n*H, where X_n is a ciphertext block
// e.g. if we need H^21*X_1 and we have shares of H^19 and H^2, we compute it as follows:
// (H19_a + H19_b)*(H2_a + H2_b)*X_1 == H19_a*H2_a*X_1 + H19_a*X_1*H2_b + H19_b*X_1*H2_a +
// H19_b*H2_b*X_1
// only the 2 middle cross-terms need to be computed using OT
// A will send OT for H19_aX to B
// B will send OT for H19_bX to A
// all other powers where one of the factors is H^2 like eg H^25 == H^23*H^2
// can be collapsed into the terms above e.g. H23_aX2 can be collapsed into H19_aX
// A will receive OT for H19_a*X_1 from B
// B will receive OT for H19_b*X_1 from A
// All other powers where one of the factors is H^2 can be "collapsed" into (i.e xored with)
// the above two cross-terms, eg if parties have shares of H^23 and need to compute
// H^25 == H^23*H^2, then H23_a*X_2 can be collapsed into H19_a*X_1 and
// H23_b*X_2 can be collapsed into H19_b*X_1
// Thus we would not need any extra OT to compute shares of H^25
async useIndirectHShares(ghashInputs){
let res = int2ba(0, 16); // this is the xor of all my X*H shares
let sumForPowers = {};
for (let i=4; i < this.powersOfH.length; i++){
if (i > ghashInputs.length){
// we will have more powers than the input blocks
// we stop iterating shares of powers of H
break;
}
if (this.powersOfH[i] != undefined){
@@ -642,12 +647,13 @@ export class TWOPC {
console.log('maxPowerNeeded is', maxPowerNeeded);
assert(maxPowerNeeded <= 1026);
// perform free squaring of shares H^2 and H^3 which we have from the Client_Finished
this.freeSquare(this.powersOfH, maxPowerNeeded);
if (this.maxOddPowerNeeded === 3){
await this.send('ghash_step1', int2ba(maxPowerNeeded, 2));
return; // already have power 3
}
// perform free squaring of shares H^2 and H^3 which we have from client finished
this.freeSquare(this.powersOfH, maxPowerNeeded);
// strategies shows what existing powers we will be multiplying to obtain other odd powers
// max sequential odd power that we can obtain on first round is 19
@@ -739,9 +745,10 @@ export class TWOPC {
throw('sum not found');
}
// Perform squaring of each share of odd power up to maxPower.
// Perform squaring of each share of odd power up to maxPower. It is "free" because we can
// compute them locally without doing OT with the other party.
// "powers" is an array where idx is the power (or undefined if not set) and item at that idx
// if client's share of H^power
// is client's share of H^power
// modifies "powers" in-place
// e.g if "powers" contains 1,2,3 and maxPower==19, then upon return "powers"
// will contain 1,2,3,4,6,8,12,16