fix median function

torusresearch · Mar 5, 2024 · a7d1ecd · a7d1ecd
1 parent b34dd1e
commit a7d1ecd
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Showing 3 changed files with 31 additions and 10 deletions.
diff --git a/src/helpers/common.ts b/src/helpers/common.ts
@@ -104,3 +104,23 @@ export function encParamsHexToBuf(eciesData: Omit<EciesHex, "ciphertext">): Omit
     mac: Buffer.from(eciesData.mac, "hex"),
   };
 }
+
+export function calculateMedian(arr: number[]): number {
+  const arrSize = arr.length;
+
+  if (arrSize === 0) return 0;
+  const sortedArr = arr.sort(function (a, b) {
+    return a - b;
+  });
+
+  // odd length
+  if (arrSize % 2 !== 0) {
+    return sortedArr[Math.floor(arrSize / 2)];
+  }
+
+  // return average of two mid values in case of even arrSize
+  const mid1 = sortedArr[arrSize / 2 - 1];
+
+  const mid2 = sortedArr[arrSize / 2];
+  return (mid1 + mid2) / 2;
+}
diff --git a/src/helpers/nodeUtils.ts b/src/helpers/nodeUtils.ts
@@ -27,7 +27,7 @@ import {
 } from "../interfaces";
 import log from "../loglevel";
 import { Some } from "../some";
-import { kCombinations, normalizeKeysResult, normalizeLegacyKeysResult, thresholdSame } from "./common";
+import { calculateMedian, kCombinations, normalizeKeysResult, normalizeLegacyKeysResult, thresholdSame } from "./common";
 import { generateAddressFromPrivKey, generateAddressFromPubKey, keccak256 } from "./keyUtils";
 import { lagrangeInterpolation } from "./langrangeInterpolatePoly";
 import { decryptNodeData, getMetadata, getOrSetNonce } from "./metadataUtils";
@@ -104,16 +104,16 @@ export const GetPubKeyOrKeyAssign = async (params: {
             // push only those indexes for nodes who are returning pub key matching with threshold pub key.
             // this check is important when different nodes have different keys assigned to a user.
             if (currentNodePubKey === thresholdPubKey) {
-              const nodeIndex = parseInt(x1.result.node_index);
+              const nodeIndex = Number.parseInt(x1.result.node_index);
               if (nodeIndex) nodeIndexes.push(nodeIndex);
             }
-            const serverTimeOffset = x1.result.server_time_offset ? parseInt(x1.result.server_time_offset, 10) : 0;
+            const serverTimeOffset = x1.result.server_time_offset ? Number.parseInt(x1.result.server_time_offset, 10) : 0;
             serverTimeOffsets.push(serverTimeOffset);
           }
         });
       }
 
-      const serverTimeOffset = Math.max(...serverTimeOffsets);
+      const serverTimeOffset = keyResult ? calculateMedian(serverTimeOffsets) : 0;
       return Promise.resolve({ keyResult, serverTimeOffset, nodeIndexes, errorResult, nonceResult });
     }
     return Promise.reject(
@@ -532,14 +532,14 @@ export async function retrieveOrImportShare(params: {
           const thresholdIsNewKey = thresholdSame(isNewKeyResponses, ~~(endpoints.length / 2) + 1);
 
           // Convert each string timestamp to a number
-          const serverOffsetTimes = serverTimeOffsetResponses.map((timestamp) => parseInt(timestamp, 10));
+          const serverOffsetTimes = serverTimeOffsetResponses.map((timestamp) => Number.parseInt(timestamp, 10));
           return {
             privateKey,
             sessionTokenData,
             thresholdNonceData,
             nodeIndexes,
             isNewKey: thresholdIsNewKey === "true",
-            serverTimeOffsetResponse: serverTimeOffset || Math.max(...serverOffsetTimes),
+            serverTimeOffsetResponse: serverTimeOffset || calculateMedian(serverOffsetTimes),
           };
         }
         throw new Error("Invalid");
@@ -685,14 +685,14 @@ export const legacyKeyLookup = async (endpoints: string[], verifier: string, ver
       lookupResults.forEach((x1) => {
         if (x1 && x1.result) {
           const timeOffSet = x1.result.server_time_offset;
-          const serverTimeOffset = timeOffSet ? parseInt(timeOffSet, 10) : 0;
+          const serverTimeOffset = timeOffSet ? Number.parseInt(timeOffSet, 10) : 0;
           serverTimeOffsets.push(serverTimeOffset);
         }
       });
     }
 
-    const serverTimeOffset = Math.max(...serverTimeOffsets);
     if (keyResult || errorResult) {
+      const serverTimeOffset = keyResult ? calculateMedian(serverTimeOffsets) : 0;
       return Promise.resolve({ keyResult, errorResult, serverTimeOffset });
     }
     return Promise.reject(new Error(`invalid results ${JSON.stringify(lookupResults)}`));

diff --git a/src/torus.ts b/src/torus.ts
@@ -15,6 +15,7 @@ import stringify from "json-stable-stringify";
 
 import { config } from "./config";
 import {
+  calculateMedian,
   encParamsBufToHex,
   generateAddressFromPrivKey,
   generateAddressFromPubKey,
@@ -404,7 +405,7 @@ class Torus {
             for (let i = 0; i < shareResponses.length; i += 1) {
               const currentShareResponse = shareResponses[i] as JRPCResponse<LegacyShareRequestResult>;
               const timeOffSet = currentShareResponse?.result?.server_time_offset;
-              const parsedTimeOffset = timeOffSet ? parseInt(timeOffSet, 10) : 0;
+              const parsedTimeOffset = timeOffSet ? Number.parseInt(timeOffSet, 10) : 0;
               serverTimeOffsets.push(parsedTimeOffset);
               if (currentShareResponse?.result?.keys?.length > 0) {
                 currentShareResponse.result.keys.sort((a, b) => new BN(a.Index, 16).cmp(new BN(b.Index, 16)));
@@ -464,7 +465,7 @@ class Torus {
             if (privateKey === undefined || privateKey === null) {
               throw new Error("could not derive private key");
             }
-            return { privateKey, serverTimeOffset: this.serverTimeOffset || Math.max(...serverTimeOffsets) };
+            return { privateKey, serverTimeOffset: this.serverTimeOffset || calculateMedian(serverTimeOffsets) };
           }
           throw new Error("invalid");
         });