Director Tie cut me short. ‘You are absolutely qualified. The fact that you have already come up with a feasible plan of action proves it. Let me be frank: various experts have already informed me that we don’t have anyone who can crack this cipher and that we are going to have to bring someone in from outside. The question is: who do you want? This is the homeland of Zu Chongzhi: we have never lacked for excellent mathematicians. We just need to find them and invite them to join us. If you can’t get them to join us, I will have a go, and if I can’t persuade them then I will find someone who can. Anyway, the point is that we can get them on board, the difficulty is finding them.’

Quite honestly, where was I supposed to look? I was just an ordinary guy who had become involved with this whole thing by chance. I had absolutely no idea what I was doing because I had only just learnt the basics of cryptography from my supervisor. I knew nothing about the situation of mathematics in China, and if you had lined up every mathematician in the country in front of me, I wouldn’t have known who to ask for.

Director Tie heard me out, and then he criticized me. ‘You are perfectly right to mention the difficulties of the problem we have set you, but you must not be frightened of them. I know the Americans have made all sorts of extravagant claims for this cipher, but we have good reason to be confident about our chances of cracking it. Sivincy is Russian, and any cipher written by her will be framed within Soviet paradigms. In recent years there has been a lot of contact between Russian and Chinese mathematicians – and indeed cryptographers – and this contact has led to understanding. This puts us in a very strong position. And another thing: you’ve spent a lot of time with Sivincy’s fellow student Anderov, and I’m sure you’ve got a lot out of it. I really feel there’s nothing to be so depressed about, and if you continue to find difficulties, you will just have to deal with them, because there is no going back! That’s the first thing I wanted to say to you.’

The second thing he said was that I had to start work right away, without delay. Find the right person, and then head straight back to Unit 701 to get busy. We could not wait any longer.