Andrew Swanston - The King's Spy

‘That depends upon the cipher used. If it is the Vigenère square again, I will have to find the keyword. In such a short message, that may be difficult. There may not be any repetitions, and the frequencies of letters are unlikely to be helpful. There are too few of them.’

‘And if it is not the square? What then?’

‘Then I should be able to break it within a day.’

‘In that case, you will attend us here tomorrow morning. We shall expect good progress, Master Hill. Pray remember that you are not a free man, and that of time we have little. If you are not able to advise me of progress when we meet again, we will be forced to consider other options.’

‘I shall do my best, your majesty.’

The king leaned forward and spoke softly. ‘Yes, Master Hill, I have no doubt that you will.’

Thomas managed a tiny bow, followed by a swift retreat. This quiet little man, with his pointed beard, his limp and his stammer, was more threatening than any hectoring bully.

Simon was waiting for him in his room. He was sitting by the window, reading the Iliad , a glass of Thomas’s wine beside him. Apart from the habit, he looked for all the world like a contented teacher of classical literature. ‘Ah, there you are, Thomas,’ he said jovially. ‘An excellent claret. I do hope you don’t mind my helping myself.’

‘The claret I do not mind, Simon. It is your unspeakable cheerfulness at this hour of the day that I find offensive. Especially as I have just come from an uncomfortable meeting with the king.’

‘Uncomfortable?’

‘Most uncomfortable. I am unable to leave the college for any reason, I am still under suspicion of murdering my old friend Abraham Fletcher and betraying secrets to the enemy, I have been deceived by Jane Romilly, and I am now expected by the king to decrypt another message.’

‘A new message? Is it our French friend again?’

‘I do hope not. The king wants it done immediately. He’s reluctant to let the queen leave Oxford without knowing what it says.’

‘Naturally. No wonder your temper is short this morning. And what of Rush?’

‘Not present. Away on the king’s business. Or pretending to be. That’s why the message has come to me.’ He paused. ‘How is Jane?’

‘Tearful. She regrets what she did and believes she has lost you. Has she lost you, Thomas?’

‘I don’t know, Simon. I trusted her, as I trusted you.’

‘Trusted, not trust?’

‘Simon, if Jane has lied to me again, so have you.’

‘We knew you would realize that. It’s exactly why I insisted she tell you the truth. All of it. And she has. Believe me.’

‘I am trying to.’

‘Good. Now, what about this message? Can I be of any assistance?’

Thomas thought for a moment. Trusted or not, a willing listener was always helpful. ‘Perhaps you can. Fill the other glass, and let us examine the problem together.’ He took the message from under his shirt and set it on the table.

XZFMGMAYTDSXPMFMMVNLAJCLAWIMELBTHXFLRYHXWIDQJQJTDDMERT

GCKETPMKEGXIEDUJIECTKOYOJDLNEPLBYEBHBKOTPMTIJLMGLPFQEBYJ

QJTDDQRWPCQKICKBIURLTZOCK

‘As you can see, it’s short. Only one hundred and thirty-six letters.’

‘And no numbers this time. Does that mean no coded words?’

‘Not necessarily, although we shall assume that to begin with.’

‘Is there any significance in the lack of spaces?’

‘I doubt it. It might signify a different sender to the last one, or it might be the same sender disguising himself. There’s no way of telling.’

‘So what now?’

Thomas held the paper up to the light of his window. The paper was good quality and the hand an educated one. He could see no distinguishing marks or hidden symbols. It had been concealed in a sword case, which suggested that the decrypted text would be simple and direct. Senders of hidden messages did not expect them to be discovered, and did not usually bother to obscure their meaning, other than with a cipher. With luck, this one had been encrypted by means of a simple alphabetic substitution cipher or a keyword. They would start with those.

‘Now we look for clues.’

‘The words MAY, LAW and KICK jumped off the page. The first two were too short to be codewords. Thomas tried KICK but knew after the first two letters that it too was merely a coincidence. They noted the repetitions of TDD, CK and QJ, decided that they were too coincidental, and had to accept that there would be no shortcut. To find a keyword or simple shift, they would have to analyse the letter frequencies.

It took them only a few minutes to count the letters and at first glance the distribution was encouraging. There was a single S and a single V, two each of N and Z, eleven Ts, ten Ms and nine Es. A good mix.’

Concen trating on the high numbers, Thomas set about finding the most common letters, E, A and T, while Simon tried the lowest numbers, looking for the least frequent letters, J, Q, X and Z. That too produced nothing, and serious doubts were creeping into Thomas’s mind. If the sender of this message had used nulls, misspellings or other trickery, the decryption would take longer, and the king would not be happy with longer.

One bottle of claret became two, food came and went, and still they had made no progress. By mid-afternoon neither of them had come up with the slightest sliver of a clue as to the method of encryption. Simon was the first to call a halt. ‘Thomas, I’m not used to this type of work. I’ve been over and over this damnable message and it has made my head ache. Shall we take a stroll?’

Thomas looked up from his page of numbers and letters. ‘Odd, that. Praying used to make my head ache. Come on then, friar. A little air may help.’

With Thomas confined to the college, there was nowhere much to stroll other than round and round the big quadrangle in the middle of which noisy cattle waited to be milked or eaten. ‘Are you really a Franciscan, Simon?’ asked Thomas suddenly.

‘Now that’s an odd question. Why would you think otherwise?’

‘The words you used about yourself. Pragmatism and humour. Not very friarly words.’

‘Monks may be recluses, friars are not. I choose to live in the same world as you. I find both qualities useful.’

‘And you don’t behave like a man of the church. You travelled to Romsey to fetch me, disguised me as one of your own, pro tected me from Rush and brought Jane to visit me in the abbey.’

‘Were these not Christian actions, Thomas? Except, perhaps, for the last, and that was a simple act of kindness to you both. Even a Franciscan knows worldly love when he sees it. Rest assured, Thomas, I am what I appear.’

‘As you wish.’ They made another circuit of the quadrangle. ‘Now, this accursed message. We’d better break it or I may not be anything much longer. This is what I think. We’ve tried everything I know and achieved nothing. I’m afraid it’s Vigenère again, this time without codewords.’

‘Why would the numbers have been omitted?’ asked Simon.

‘The strength of codes is that they can be quickly decoded by the intended recipient. In the case of the square, they also make the frequency analysis harder by reducing the number of letters in the text. This is a very short message, which in itself is protection against decryption. If the keyword has, say, five letters, there will be no more than twenty-seven letters in each group. Too few to be much use, although I shall of course try.’

‘And do you see Rush behind it?’

‘I do. He’s no fool. He suggested to the king that I show them how the decryption of the last message worked, and he’s realized that, unless the text is short, the length of a keyword can be worked out. And he may have inserted nulls or misspellings, or both, to throw unwelcome hounds off his scent. Why otherwise would the encryption be as it is? If Rush wrote this message, it may well concern the queen, and we must discover its contents.’