diff --git a/src/main/java/racal/sunyard/main/SydApi4j.java b/src/main/java/racal/sunyard/main/SydApi4j.java
index b065dc9..5a54330 100644
--- a/src/main/java/racal/sunyard/main/SydApi4j.java
+++ b/src/main/java/racal/sunyard/main/SydApi4j.java
@@ -7923,6 +7923,70 @@ public class SydApi4j implements SydApi {
         }
     }
 
+
+    /**
+     * 自动 4k 分包
+     * @param keyType
+     * @param mode
+     * @param key
+     * @param msg
+     * @return MAC 值
+     */
+    public String genMAB(int mode, int keyType, String key, byte[] msg){
+        final int blockSize = 4 * 1024;
+        if ( null == msg || msg.length == 0 ) {
+            throw new SydApiException("输入数据为空", 21);
+        }
+
+        if( msg.length <= blockSize ) {
+            // 唯一包
+            RetWrap retWrap = this.genMAB(0, keyType, 2, key, null, msg );
+            return new String( (byte[])  retWrap.get("MAB") );
+        }
+
+        int loop = 0;
+        int tailLen = 0;
+
+        loop = msg.length / blockSize;
+        tailLen = msg.length % blockSize;
+        if (tailLen > 0) {
+            loop++;
+        }
+
+        // loop 至少是 2
+
+        // 分包数据
+        byte[] data = null;
+
+        // 首包
+        // 必然有
+        data = new byte[ blockSize ];
+        System.arraycopy( msg, 0, data, 0 , data.length );
+        RetWrap retWrap = this.genMAB(1, keyType, 2, key, null, data );
+        byte[] iv = (byte[]) retWrap.get("MAB");
+
+
+        // 中间包
+        for ( int i = 0 ; i < (loop - 2); i++ ) {
+            data = new byte[ blockSize ];
+            System.arraycopy( msg, (i + 1) * blockSize , data, 0 , data.length );
+            retWrap = this.genMAB(2, keyType, 2, key, iv, data );
+            iv = (byte[]) retWrap.get("MAB");
+        }
+
+
+        // 尾包
+        // 必然有
+        if( 0 == tailLen ) {
+            // 恰好是分包整倍数
+            tailLen = blockSize;
+        }
+        data = new byte[ tailLen ];
+        System.arraycopy( msg, (loop - 1) * blockSize , data, 0 , data.length );
+        retWrap = this.genMAB(3, keyType, 2, key, iv , data);
+        return new String( (byte[])  retWrap.get("MAB") );
+    }
+
     /**
      * 8.3用对大消息生成MAC（MAB）(*)  -> pass
      *