C506 Decrypting Top-secret Documents

What do these symbols mean? Xie Qian thought hard, and his head was about to explode. He fiercely kicked the black stool.

He smoked, one cigarette after another.

The last few characters were different from the previous ones. He copied and opened the first one. Only now did he see two Mandarin characters, Attachment, in the corner. The characters were small and hard to find