在钥匙链中存储当前设备是否为旧设备，旧设备指用户登录过的设备。Review by 硬币。

@@ -61,5 +61,7 @@
 + (NSString*) value;
 + (NSString*) valueWithError:(NSError**)error;
 + (void) setOptOut:(BOOL)optOutValue;
++ (void) setUsedDevice;
++ (BOOL) isNewDevice;
 
 @end

@@ -68,6 +68,7 @@ static NSString * const kOpenUDIDSlotPBPrefix = @"org.OpenUDID.slot.";
 static int const kOpenUDIDRedundancySlots = 100;
 static NSString * const kYohoSecretInfo = @"com.yoho.buy.secretinfo";
 static NSString * const kYohoBuyUdid = @"com.yoho.buy.udid";
+static NSString * const kYohoBuyUsedDevice = @"com.yoho.buy.useddevice";
 
 @interface OpenUDID (Private)
 + (void) _setDict:(id)dict forPasteboard:(id)pboard;
@@ -392,4 +393,24 @@ static NSString * const kYohoBuyUdid = @"com.yoho.buy.udid";
     
 }
 
++ (void) setUsedDevice
+{
+    NSMutableDictionary *yohoinfoKVPairs = (NSMutableDictionary *)[YH_KeychainStore load:kYohoSecretInfo];
+    if (yohoinfoKVPairs == nil) {
+        yohoinfoKVPairs = [NSMutableDictionary dictionary];
+    }
+    [yohoinfoKVPairs setObject:@"Y" forKey:kYohoBuyUsedDevice];
+    [YH_KeychainStore save:kYohoSecretInfo data:yohoinfoKVPairs];
+}
+
++ (BOOL) isNewDevice
+{
+    NSMutableDictionary *yohoinfoKVPairs = (NSMutableDictionary *)[YH_KeychainStore load:kYohoSecretInfo];
+    if (yohoinfoKVPairs == nil || yohoinfoKVPairs[kYohoBuyUsedDevice] == nil) {
+        return YES;
+    } else {
+        return NO;
+    }
+}
+
 @end