‘That was my first deduction concerning RECOVERY,’ Huang Yiyi went on. ‘This isn’t an ordinary cipher and it also isn’t particularly difficult, but in its cunning, artfulness, innovativeness, fascination and cleverness, it is more like a wonderful magic trick. A magic trick may not be very difficult to perform, yet it can perplex you in the same way that a cipher can. Sivincy may well have constructed a magic cipher, to trick other cryptographers.’

‘An eccentric genius like Sivincy might well enjoy pulling that kind of trick,’ I said.

‘Right. That was the reason I made this deduction.’

I was getting interested, and rubbed my hands together. ‘Fascinating! Really fascinating!’

Huang Yiyi showed that she wasn’t entirely happy with her theories when she said, ‘When my deductions about the cipher key didn’t work out, I was very upset, and I started to wonder if all my ideas were wrong. That was when I came up with a new theory: that this is an algorithmic cipher encrypted with an algorithmic cipher. If you asked someone like Sivincy, with such a massive reputation and with such impressive mathematical abilities, to create a conventional cipher, she would certainly choose that route because it would allow her to demonstrate her talents as a mathematician. But I have been moving that way for such a long time and I simply don’t feel I have got anything out of it, so perhaps it is time to wrap it up. You think that Sivincy wouldn’t have designed RECOVERY that way either?’

I nodded.

She then said: ‘I have a very strong feeling that Sivincy is most likely to have incorporated classic encryption techniques into RECOVERY, and even though my theories didn’t work out, this feeling has never gone away.’ She sighed deeply. ‘Maybe I do have to go right back to the beginning.’

That day the longer we talked, the deeper we became caught up in what we were doing, and the more excited we became, until we found that we had been chatting for several hours. We discussed with complete freedom the theories that we had and the ideas that had struck us. It was wonderful! But while Huang Yiyi and I were chatting so happily, I couldn’t help hearing Comrade Chen’s footsteps pacing up and down the corridor many times, ever more impatient and stubborn. At that time I had no idea what Chen’s angry footsteps meant, and when I did understand, it was too late.

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