Mai Jia - Decoded

Now here was Jan Liseiwicz specifically warning Rong Jinzhen not to touch PURPLE. On the one hand that demonstrated that PURPLE would indeed be very difficult to decrypt and that if he tried, he would not get anything out of it; but on the other hand it also made it clear that Liseiwicz must know something about how PURPLE worked. From the letters that he had sent to date, it was clear that he and Jinzhen were unusually close. If they were able to make use of that affection, they might find a way to make him disgorge some useful information. So a letter was sent back to Jan Liseiwicz, signed with Jinzhen’s name.

The letter was typed; only the signature at the bottom was handwritten. It looked like Rong Jinzhen’s signature, but it was forged. To put it bluntly — at least in this matter, Rong Jinzhen was being used by the Party. The aim of writing back to Liseiwicz was to help with the decryption of PURPLE — why did they have to let Jinzhen know what was going on when he spent all day reading his novels and playing chess with a lunatic rather than getting on with his work? Besides which, if they had let him write the letter himself, he would not necessarily have come up with anything as good as what they did — the first draft was prepared by five experts and it was approved by three of the directors before it was sent. The burden of the message, couched in the most sincere and respectful terms was simple: ‘Why can’t I decrypt PURPLE?’

Apparently all this sincerity and respect had its effect since Liseiwicz wrote back extremely quickly; a letter filled with sincere advice. He began by bewailing the fact that his dream was correct and upbraiding Jinzhen for being so stupid as to take this path. He seemed to see it as a sign of the unfairness of fate. After that, he went on to write:

I feel an irresistible impulse to tell you my secret — I really don’t understand why. Maybe when I have written this letter and posted it, I will regret what I have done. I swore an oath that I would never tell anyone this secret, but for your sake, I have to speak. .

What secret?

In the letter, Liseiwicz explained that in the winter of the year that he brought the two packing-cases of books back to the university, he was originally planning to start work researching artificial intelligence. However, the following spring, an important personage in the newly established state of Israel came to visit him. This person said, ‘It has long been the dream of all Jewish people to have our own homeland. However, we are now faced with enormous problems. Are you prepared to see your own people suffer any more than they have already?’

Liseiwicz replied, ‘Of course not.’

‘Then I hope that you are going to do something for us,’ his visitor said.

‘What?’

Liseiwicz explained in his letter: ‘They wanted me, on behalf of the Israeli government, to decrypt a couple of the military ciphers in use among neighbouring countries. I did this kind of work for the next couple of years.’ That must have been what Liseiwicz was referring to in the letter he left for Young Lillie when he and his family departed for X country: ‘The last few years I have been working on something very important on their behalf — the troubles that they have faced and their hopes for the future have moved me deeply; for their sake I have given up a long cherished ambition.’ Liseiwicz went on to write: ‘I was very lucky. After they began employing me in this work, I was able to decrypt quite a few mid-level and a couple of high-level ciphers being used by neighbouring countries without too many problems. Pretty quickly I was just as famous in the world of cryptography as I had ever been in the world of mathematics.’

That made what happened next so much clearer. It explained why X country was so determined to help him at all costs, why they took him and his family away — it was because they were hoping to be able to make use of his cryptographic abilities. But after he arrived in X country, things had worked out completely differently from anything Liseiwicz could have imagined. As he wrote:

I could never in my wildest dreams have imagined that they wanted me to come not because they were hoping that I would be able to decrypt enemy ciphers but because they wanted me to decrypt one of their own: PURPLE! I am sure that I do not need to tell you that the moment I can decrypt it — maybe even the moment I get close — it is going to be rendered obsolete. My job is to decide whether PURPLE lives or dies. I am effectively a signal, informing X country of when the enemy is likely to have got close to cracking PURPLE. Maybe I ought to feel proud of this; they clearly think that if I can’t decrypt PURPLE then no one can. I don’t know why; maybe it is because I don’t like the role in which I have been cast, maybe it is because I don’t like people claiming that PURPLE can never be broken — anyway, for whatever reason I have become particularly determined to decrypt it. But up to the present moment I have not even begun to feel my way towards a method for doing so — that is why I am telling you not to even think about touching PURPLE yourself. .

The people reading this missive noticed a couple of striking things about it — the handwriting and sender’s address were completely different from previous letters, which means that Liseiwicz was well aware of how dangerous his actions were — in sending this letter he could easily have been accused of treason. It also demonstrated how genuinely fond of Jinzhen he was. It seemed entirely possible that this affection could be used and so another letter signed with Jinzhen’s name was sent to Liseiwicz in X country. In this letter, the false Jinzhen was clearly trying to use the professor’s fondness for his former student to force him into making some kind of disclosure:

I have lost my freedom. If I wish to recover it, I have to decrypt PURPLE. . I am sure that after working on PURPLE all these years you can offer me a few pointers to guide me through the maze. . I have no experience in this kind of work, I need advice; any advice would be useful. . Dear Professor Liseiwicz, curse me if you like, spit at me, hit me, I feel like a Judas. .

It was of course impossible to post a letter with this kind of content straight to Jan Liseiwicz. In the end it was decided to send it first to some of our comrades in X country, who would arrange for it to be privately delivered. Even though they could be quite sure that it would arrive safely; as to whether or not Liseiwicz would reply, the people at Unit 701 were far from feeling confident. After all, this Jinzhen — the false Jinzhen — really was a Judas; most professors would not pay the blindest bit of attention to a student like that. To put it another way, this false Jinzhen was nicely poised between being pitiful and being despicable. Getting someone like Liseiwicz to ignore the despicable features and concentrate on the pitiable ones was going to be quite as difficult as cracking PURPLE. Sending this letter really was just trying their luck; it tells you that the cryptography division at Unit 701 was so desperate at this point that they would try anything.

Well, the miracle happened and Liseiwicz wrote back! During the next six months, Liseiwicz repeatedly risked a traitor’s death to contact our comrades, giving ‘dear Jinzhen’ a mass of material about PURPLE and suggesting ways to proceed in decrypting it. As a result, headquarters decided to temporarily create a PURPLE decryption working group, providing the majority of the cryptographers themselves. They were told to crack this difficult nut as quickly as they could. No one had any idea that Rong Jinzhen would be ahead of them all! In actual fact, by this time Liseiwicz had been patiently writing to Jinzhen for the best part of a year, without Rong Jinzhen having received a single letter — he didn’t even know the first thing about what was going on. That means that these letters meant nothing to him — if they affected him at all, it was by lifting the pressure a little bit. After all, when the directors realized that Jinzhen wasn’t working hard at his ciphers (in fact if anything he was even worse than before) they could easily have got rid of him as a complete waste of space — but the fact is that the Party decided to leave him alone. They did not need his input. He was going to be the bait that would allow them to decrypt PURPLE.