diff --git a/ServerDocument.md b/ServerDocument.md
index 0849971..d1e69f3 100644
--- a/ServerDocument.md
+++ b/ServerDocument.md
@@ -35,4 +35,43 @@
         sig:  签名
         
     第三方server端返回值：
-        如果第三方验证成功，则返回字符串：success即可。
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+        如果第三方验证成功，则返回字符串：success即可。
+        
+        
+3.签名算法
+--------------------------------
+
+
+···java
+
+	/**
+	 * 签名算法
+	 * @param userOrder
+	 * @param key
+	 * @return
+	 */
+	private String sig(UserOrder userOrder, String key) {
+
+		SortedSet<String> allParams = Sets.newTreeSet();
+		try {
+			
+			allParams.add(Constants.Keys.ORDER_ID + "=" + URLEncoder.encode(userOrder.getId()+"", "utf-8"));
+			allParams.add(Constants.Keys.APPID + "=" + URLEncoder.encode(userOrder.getAppId()+"", "utf-8"));
+			allParams.add(Constants.Keys.USER_ID + "=" + URLEncoder.encode(userOrder.getUserId()+"", "utf-8"));
+			allParams.add(Constants.Keys.PRODUCT + "=" + URLEncoder.encode(userOrder.getProduct(), "utf-8"));
+			
+			allParams.add(Constants.Keys.EXTRA_INFO + "=" + URLEncoder.encode(userOrder.getExtraInfo(), "utf-8"));
+			allParams.add(Constants.Keys.CURRENCY + "=" + URLEncoder.encode(userOrder.getCurrency(), "utf-8"));
+			allParams.add(Constants.Keys.AMOUNT + "=" + URLEncoder.encode(userOrder.getAmount()+"", "utf-8"));
+			allParams.add(Constants.Keys.REAL_AMOUNT + "=" + URLEncoder.encode(userOrder.getRealAmount()+"", "utf-8"));
+			
+		} catch (UnsupportedEncodingException e) {
+			e.printStackTrace();
+		}
+		
+		String params = Joiner.on("&").join(allParams) + key;
+		log.info("sig:" + params);
+		String computedToken = DigestUtils.md5DigestAsHex(params.getBytes());
+		return computedToken;
+	}
+···
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