revert: undo incorrect threshold conversion that broke keygen

Reverts e81757ad - the threshold conversion was wrong.
Keygen works with original thresholdT/thresholdN parameters.
The signing issue needs a different fix.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/mpc-system/services/service-party-app/electron/main.ts

@@ -1226,54 +1226,16 @@ function setupIpcHandlers() {
         return { success: false, error: '请先连接到消息路由器' };
       }
 
-      // Support both old format (thresholdT, thresholdN) and new format (requiredSigners, totalParties)
-      // New format uses user-friendly "required signers" which needs conversion to tss-lib threshold
-      let thresholdT: number;
-      let thresholdN: number;
-      let externalCount: number;
-      let persistentCount: number;
-
-      if (params.requiredSigners !== undefined && params.totalParties !== undefined) {
-        // New format: Convert user-friendly parameters to tss-lib parameters
-        // In tss-lib, threshold_t means you need (t+1) parties to sign
-        // So if user wants 3 signers, threshold_t = 3 - 1 = 2
-        const requiredSigners = params.requiredSigners;
-        const totalParties = params.totalParties;
-
-        thresholdT = requiredSigners - 1;  // tss-lib threshold
-        thresholdN = totalParties;
-        externalCount = requiredSigners;   // user parties = required signers
-        persistentCount = totalParties - requiredSigners;  // server backup parties
-
-        console.log('[CreateSession] Converting user-friendly params to tss-lib:', {
-          requiredSigners,
-          totalParties,
-          'tss-lib threshold_t': thresholdT,
-          'tss-lib threshold_n': thresholdN,
-          externalCount,
-          persistentCount,
-        });
-      } else {
-        // Old format: Use thresholdT and thresholdN directly (backward compatible)
-        thresholdT = params.thresholdT;
-        thresholdN = params.thresholdN;
-        // 动态计算 server-party 数量: persistent = n - t
-        // 例如: 2-of-3 -> persistent=1, 3-of-5 -> persistent=2, 4-of-7 -> persistent=3
-        persistentCount = thresholdN - thresholdT;
-        externalCount = thresholdT;
-
-        console.log('[CreateSession] Using legacy params (backward compatible):', {
-          thresholdT,
-          thresholdN,
-          externalCount,
-          persistentCount,
-        });
-      }
+      // 动态计算 server-party 数量: persistent = n - t
+      // 例如: 2-of-3 -> persistent=1, 3-of-5 -> persistent=2, 4-of-7 -> persistent=3
+      // 这样平台备份方数量等于"允许丢失的份额数"，确保用户丢失密钥后仍可恢复
+      const persistentCount = params.thresholdN - params.thresholdT;
+      const externalCount = params.thresholdT; // 用户持有的份额数量
 
       const result = await accountClient?.createKeygenSession({
         wallet_name: params.walletName,
-        threshold_t: thresholdT,
-        threshold_n: thresholdN,
+        threshold_t: params.thresholdT,
+        threshold_n: params.thresholdN,
         initiator_party_id: partyId,
         initiator_name: params.initiatorName || '发起者',
         persistent_count: persistentCount,
@@ -1309,8 +1271,8 @@ function setupIpcHandlers() {
             partyIndex: joinResult.party_index,
             participants: participants,
             threshold: {
-              t: thresholdT,
-              n: thresholdN,
+              t: params.thresholdT,
+              n: params.thresholdN,
             },
             walletName: params.walletName,
             encryptionPassword: '', // 不使用加密密码

backend/mpc-system/services/service-party-app/src/pages/Create.tsx

@@ -13,11 +13,8 @@ export default function Create() {
   const navigate = useNavigate();
 
   const [walletName, setWalletName] = useState('');
-  // requiredSigners: 用户选择的"需要几人签名"（用户直观理解）
-  // 例如：用户选择 3 表示需要 3 人签名
-  // 在 tss-lib 中，threshold_t = requiredSigners - 1（因为 tss-lib 需要 t+1 人签名）
-  const [requiredSigners, setRequiredSigners] = useState(3);
-  const [totalParties, setTotalParties] = useState(5);
+  const [thresholdT, setThresholdT] = useState(3);
+  const [thresholdN, setThresholdN] = useState(5);
   const [participantName, setParticipantName] = useState('');
   const [isLoading, setIsLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
@@ -33,15 +30,15 @@ export default function Create() {
       setError('请输入您的名称');
       return;
     }
-    if (requiredSigners > totalParties) {
-      setError('签名人数不能大于参与方总数');
+    if (thresholdT > thresholdN) {
+      setError('签名阈值不能大于参与方总数');
       return;
     }
-    if (requiredSigners < 2) {
-      setError('签名人数至少为 2');
+    if (thresholdT < 1) {
+      setError('签名阈值至少为 1');
       return;
     }
-    if (totalParties < 2) {
+    if (thresholdN < 2) {
       setError('参与方总数至少为 2');
       return;
     }
@@ -51,17 +48,10 @@ export default function Create() {
     setError(null);
 
     try {
-      // Pass user-friendly parameters directly
-      // main.ts will convert to tss-lib parameters
-      console.log('[Create] Sending parameters:', {
-        requiredSigners,
-        totalParties,
-      });
-
       const createResult = await window.electronAPI.grpc.createSession({
         walletName: walletName.trim(),
-        requiredSigners,
-        totalParties,
+        thresholdT,
+        thresholdN,
         initiatorName: participantName.trim(),
       });
 
@@ -132,23 +122,23 @@ export default function Create() {
             </div>
 
             <div className={styles.inputGroup}>
-              <label className={styles.label}>签名设置</label>
+              <label className={styles.label}>阈值设置 (T-of-N)</label>
               <div className={styles.thresholdConfig}>
                 <div className={styles.thresholdItem}>
-                  <span className={styles.thresholdLabel}>需要签名人数</span>
+                  <span className={styles.thresholdLabel}>签名阈值 (T)</span>
                   <div className={styles.numberInput}>
                     <button
                       className={styles.numberButton}
-                      onClick={() => setRequiredSigners(Math.max(2, requiredSigners - 1))}
-                      disabled={requiredSigners <= 2}
+                      onClick={() => setThresholdT(Math.max(1, thresholdT - 1))}
+                      disabled={thresholdT <= 1}
                     >
                       -
                     </button>
-                    <span className={styles.numberValue}>{requiredSigners}</span>
+                    <span className={styles.numberValue}>{thresholdT}</span>
                     <button
                       className={styles.numberButton}
-                      onClick={() => setRequiredSigners(Math.min(totalParties, requiredSigners + 1))}
-                      disabled={requiredSigners >= totalParties}
+                      onClick={() => setThresholdT(Math.min(thresholdN, thresholdT + 1))}
+                      disabled={thresholdT >= thresholdN}
                     >
                       +
                     </button>
@@ -156,24 +146,24 @@ export default function Create() {
                 </div>
                 <div className={styles.thresholdDivider}>of</div>
                 <div className={styles.thresholdItem}>
-                  <span className={styles.thresholdLabel}>参与方总数</span>
+                  <span className={styles.thresholdLabel}>参与方总数 (N)</span>
                   <div className={styles.numberInput}>
                     <button
                       className={styles.numberButton}
                       onClick={() => {
-                        const newN = Math.max(3, totalParties - 1);
-                        setTotalParties(newN);
-                        if (requiredSigners > newN) setRequiredSigners(newN);
+                        const newN = Math.max(2, thresholdN - 1);
+                        setThresholdN(newN);
+                        if (thresholdT > newN) setThresholdT(newN);
                       }}
-                      disabled={totalParties <= 3}
+                      disabled={thresholdN <= 2}
                     >
                       -
                     </button>
-                    <span className={styles.numberValue}>{totalParties}</span>
+                    <span className={styles.numberValue}>{thresholdN}</span>
                     <button
                       className={styles.numberButton}
-                      onClick={() => setTotalParties(totalParties + 1)}
-                      disabled={totalParties >= 10}
+                      onClick={() => setThresholdN(thresholdN + 1)}
+                      disabled={thresholdN >= 10}
                     >
                       +
                     </button>
@@ -181,7 +171,7 @@ export default function Create() {
                 </div>
               </div>
               <p className={styles.hint}>
-                需要 {requiredSigners} 个参与方共同签名才能执行交易 (其中 {totalParties - requiredSigners} 个由平台托管用于备份)
+                需要 {thresholdT} 个参与方共同签名才能执行交易 (其中 2 个由平台托管用于备份)
               </p>
             </div>
 

backend/mpc-system/services/service-party-app/src/types/electron.d.ts

@@ -112,12 +112,8 @@ interface Settings {
 
 interface CreateSessionParams {
   walletName: string;
-  // New format: user-friendly parameters (preferred)
-  requiredSigners?: number;  // Number of signers needed (e.g., 3 for "3-of-5")
-  totalParties?: number;     // Total parties (e.g., 5 for "3-of-5")
-  // Legacy format: tss-lib parameters (backward compatible)
-  thresholdT?: number;       // tss-lib threshold (requiredSigners - 1)
-  thresholdN?: number;       // Same as totalParties
+  thresholdT: number;
+  thresholdN: number;
   initiatorName: string;
 }