by Dave Duncan
Vasco nodded uncertainly.
“Alfeo told you how easy it is to break a Caesar cipher. But if you use several Caesars by turn, then the cipher becomes unbreakable! Or so the sagacious Belaso believed and later authorities have agreed. The only thing you need to establish in advance with your correspondent is the order in which you will use the alphabets. No? Well, let us attempt an example. A little farther down the page write the sentence, ‘Sciara, who is furtive.’ In uppercase letters, if you please.”
Vasco wrote, SCIARA, CHE E CIRCOSPETTO.
“And then put it in five-letter groups, as Algol does.”
SCIAR ACHEE CIRCO SPETT O
The Maestro pressed his fingertips together, enjoying his lecture. “Now we shall apply the key, and in this case the word will be VIRTU, as that was Algol’s choice. The man has a sense of irony, if not humor. Pray write that under each of the groups.”
SCIAR ACHEE CIRCO SPETT O
VIRTU VIRTU VIRTU VIRTU V
“Excellent. Now leave a line and write out the normal alphabet again. Good. Under it write the Caesars you will use to encipher your plaintext.” He frowned at Vasco’s blank stare-he is accustomed to dealing with my less-circumscribed intelligence. “The first row, you begin with a V… VXZAB…and end with U. The next begins IJLMN…”
It took a while and Vasco’s rows and columns were not as straight as might be desired, but he got there. The Maestro was beaming.
“Excellent! We’ll make a scribe out of you yet. Now to begin the encipherment! Under the first letter of the plaintext, S, you see the V of VIRTU, yes? So you find S in the normal alphabet, the one that begins with A, and go down to the alphabet that begins with V and what letter do you find?”
Thoroughly bewildered, Vasco did not find any, so I directed him to P, and he wrote it underneath the S, as instructed. The next letter, C, on the I alphabet, came out as B, and so on. By the time he reached the middle of the second group, he was managing by himself and I was making admiring noises.
SCIAR ACHEE CIRCO SPETT O
VIRTU VIRTU VIRTU VIRTU V
PBLTN VLAZ…
“This is absolutely brilliant!” I said. “How in the world did you do it?”
The Maestro made no effort to appear modest. “The pattern you noticed indicated that a letter’s position within each group was important, so I tried a frequency analysis on the initial letter of each group. It showed too many B ’s, so I hypothesized that B stood for either E or A, in which case the Caesar alphabet began with either V or B. Then I tried the second letter of each group, and so on. A rigorous analysis would require more plaintext than just one page, but I found enough clues to work out that the key must be VIRTU . It was not so difficult once I recalled the theories of Trithemius, Cardano, Porta, and so on. I’m astonished Sciara and his rabble did not see it. I admit, though,” he added, being hypocritically gracious, “that I have never heard of polyalphabetic substitution ever being used in practice.”
He had been lucky. Che is not merely a common word in itself; that combination of letters appears in many words in both Tuscan and Veneziano. Whenever it fell in the middle of a five-letter group, it had enciphered as my initials, which had caught my eye. In any other position it was represented by some other triplet, and with another key word it might always be. Then we would not have noticed the repetition. The best ciphers are broken because of human error, Nostradamus had told us, and Algol should never have left the ciphertext in five-letter groupings. That was incredible carelessness.
Vasco, meanwhile had completed the enciphering and was staring in bewilderment at the result:
PBLTN VLAZA ZRJVJ L
He had not even noticed my LAZ in there.
“So there you are, Vizio,” the Maestro said. “That is how it is enciphered. Now let us try some deciphering. We need to know if the same keyword will work for all four intercepted messages. Page one of one, if you please.”
With surprisingly little help from me, Vasco managed to reverse the process and start recovering the original plaintext:
XIAGO ILCON SIGLI ODEID E…
He stopped. “This is gibberish!”
The Maestro sighed. “Perhaps the key word is not the same, then.” He was carefully not looking at me, who could read over Vasco’s shoulder. Unlike Vasco, though, I was reading: 11 Agosto. Il Consiglio dei Deci…*
“Let us try the final dispatch then. Page one of four, please.”
Again Vasco balked after a few groups, but this time a ray broke through the clouds. “Wait a moment! They begin with dates!”
XVSET TILPR ESDI…
15 Settembre. Il presidio…*
“Why, so they do!” I cried.
The game was over. Vasco hastily covered his work with his hands.
“You don’t need to see this!”
“Of course not,” the Maestro agreed. “You can let Missier Grande into the secret and he can decipher the rest.”
But I was confident that the Maestro himself would break the news to Circospetto, so he could watch Sciara gnash his fangs in mortification. Vasco looked at him as if suspecting the sort of elaborate hoax that I love to play on him every time I get the chance, but which the Maestro considers beneath his dignity.
“This nonsense will translate everything?”
Nostradamus sighed and opened a drawer. “Here is a deciphered version of the page you left in the dining room.”
It was his own version, and Vasco needed some time to decipher the scrawl and artificial letter groups. As he did, he grew paler and paler.
“The interesting thing,” the Maestro remarked, and now he was looking at me, although his expression gave away nothing, “was that Circospetto lied to us.”
“Yes, he did,” I agreed. Today was September 23. If Algol’s fourth dispatch reported news of events on September 15, there had not been time for it to reach Constantinople and the Republic’s spy there to copy it and report back to Venice. Of all the states Algol might be working for, even Rome, the closest, would require almost impossible timing. If the Ten were opening Algol’s mail right here in the city, why did they not know the sender?
Vasco would never work that out, but before he rose to the bait, the door swung wide and in marched Bruno, carrying a bundle of firewood that would have flattened me. We have taught him to knock on doors, but he does not understand “audibly,” so it does no good. Beaming at us, he delivered his burden to the hearth, then strode out again, leaving the door open.
“Chilled?” Vasco inquired icily.
“Important business,” the Maestro said. “I must report to the chiefs. You are welcome to accompany us, Vizio. Go and pack up your things. You can be of no further use here.”
Almost no other commoner in Venice would have dared speak to Vasco like that, but he took it from the Ten’s consultant. Glowering at me to indicate that our temporary truce was now ended, he stuffed the latest paper in his satchel and departed.
The Maestro detests having to go out, and I could not recall him ever doing so two days in a row. He must be expecting a handsome reward, in satisfaction, if not in coin. I hurried to my room to don my best. This time I decided to sacrifice good manners on the altar of security, for I knew we were on dangerous business and would be lacking Filiberto’s dubious protection on the way home. I retrieved my rapier and dagger from the top of the wardrobe.
As Giorgio’s strong oar sped us along the Grand Canal toward the Doges’ Palace, I heard the bells of San Giacomo di Rialto tolling sunset.
13
S o we returned to the palace and the same chamber we had left not twenty-four hours earlier, the Sala dei Tre Capi. The three chiefs themselves must have been rounded up especially to hear our report, for we were kept waiting only a few minutes and Marino Venier still had crumbs in his beard. The Pope himself could not have asked for greater deference than that. Obviously the government was still extremely worried; La Serenissima was anything but serene.
The heat of the day had left t
he room stifling. The lamps were lit, but their glimmer hardly showed against the remains of daylight. As the Maestro shuffled in, leaning on my shoulder, the chiefs were just settling behind their raised table, and the only aide in sight was Raffaino Sciara, the Grim Reaper in blue. Vasco had left us, gone to report to Missier Grande, no doubt. Sciara placed a chair for the Maestro and retreated to the secretaries’ desk. I saw my master seated, then took my place behind him.
Three old men peered anxiously down at Nostradamus.
Trevisan was in the center. “Well, Doctor? You wasted no time. What news?”
I had never seen the Maestro’s pussycat smile better displayed.
“I have not yet identified your Algol, messere, although I have my suspicions. To confirm or disprove those will take a little longer, but I am satisfied that he exists and I have broken his cipher. I deemed this sufficient cause to interrupt your supper.”
Six eyes turned toward Raffaino Sciara. I looked at him also, because I had never seen a skull look humiliated before.
“You will show Their Excellencies the restored plaintext?” Circospetto demanded acidly.
“I did not venture to pry into it all,” the Maestro said with false humility. I could tell he was enjoying himself hugely, although the others might not be reading the signals. “I have no need to know the Republic’s secrets. I deciphered one page, just to be sure, and most of it seemed to be street gossip with a few nuggets of intelligence. I can confirm that the key is the same in all the four documents. Alfeo?” He handed me the fair copy I had made for him, and I stepped forward to hand it up to Trevisan. Three heads almost banged together as the chiefs all tried to read it at once.
“So what is the cipher?” Sciara demanded, quite as furious now as he was supposed to be.
“A simple polyalphabetic,” the Maestro said mildly.
“I am impressed, Doctor.” Sciara had to admit that, however sourly, after his minions had failed to crack it. “I have always understood that there was no way of breaking a polyalphabetic cipher.”
The three chiefs were still muttering together, jabbing fingers at the plaintext.
“The simple Cardano form used by this Algol person is vulnerable,” the Maestro said, rubbing salt in the wound. “Had he followed the subtler recommendations of the sagacious Monsieur Vigenere and used the plaintext to encode itself, then even I might have failed to break it. As it is, I showed it all to Filiberto Vasco. He will explain the technique to you.” He stretched his lips in a helpful smile.
I came very close to exploding. The thought of Sciara taking lessons from dear Filiberto was exquisite.
“We are deeply impressed, Doctor,” Marino Venier growled. “This document appears to be genuine. As you saw, it does include some covert information.” The chiefs were all smiling, though. Their decision to consult Nostradamus had borne fruit and the skeptics within the Ten would have to eat their doubts. “You said you had other evidence for us?”
“Nothing that you can put before a court, messere. May I inquire who named this spy ‘Algol’?”
The heads exchanged glances. The outer two nodded. Trevisan said, “We have reason to believe that his employers refer to him by that name. A codeword or a joke, perhaps.”
“I fear it may be more,” the Maestro said. “I may speak in confidence, messere?”
“You have certainly earned that right.”
I certainly did not expect him to mention that his foresight had been blurred or my tarot confused, for that would be tantamount to a confession of practicing witchcraft, but he came close.
“I have detected occult interference with my work. I have even had a premonition that Algol will seek to entrap me, planning to destroy my usefulness to the Republic.”
“We shall provide additional guards!” Soranzo barked as the other two spluttered in alarm.
That was the last thing Nostradamus wanted. “No, messere! I do not expect the entrapment to take the form of physical violence, for that would be too easily traced back to him. The attack will be of a supernatural essence. I can take steps to defend myself and sier Alfeo from it, but others would be more vulnerable. Even the admirable vizio -and I assure you that I have absolute faith in Filiberto Vasco’s loyalty and dedication-even the vizio could be corrupted by black art. I ask that you remove him from my premises. His sword cannot defend against the powers of darkness, and he may merely get in the way of what I propose to do.”
Neatly done, I thought. He had used Vasco to rid himself of Danese and now was getting rid of Vasco also. That would be convenient, as long as he did not find Algol taking their place.
“May we inquire exactly what that is?” Soranzo asked narrowly. “Just what are you proposing to do?” Although far from being an outright skeptic like the doge, he was ranking doubter among the three chiefs.
“I propose to unmask Algol,” the Maestro said testily. “Quite apart from menacing the beloved Republic of which I have the honor of being an adopted citizen, he has used demonic powers against me and my apprentice, an intrusion I shall not tolerate. Doubtless he was originally a loyal subject of his ruler, who believed that he was serving a noble cause when he began to dabble in black arts, but the laws of demonology are infrangible, and he has undoubtedly fallen into the power of the Powers he sought to control. I shall identify him and report him to-”
I thought for a moment that he was going to continue, “-Holy Mother Church for exorcism.” That would have been disastrous. The last thing Venice ever wants is the Vatican trying to meddle in its affairs of state. He caught himself in time. “-your honored selves.”
The chiefs had sensed the hesitation and were frowning.
“Just how do you propose to identify this demon-wielder you describe?” Trevisan demanded, perhaps imagining holy water being splattered in all directions in the name of the Council of Ten. That would not do, either.
“No demon-wielder, clarissimo. A damned soul, fallen into the clutches of the Evil One. There is a procedure…I do not contemplate black magic, Your Excellencies, but of invoking certain elementals, spirits that are morally neutral, neither good nor evil. Fire elementals are particularly attuned to demons, understandably, but are not in themselves damned, because fire is one of God’s boons to mankind. Fire can purify or it can destroy. Certain ancient authorities list some obscure procedures to elicit the aid of these spirits. I believe it would be possible to call on them to identify the possessed person or persons.”
Soranzo rolled his eyes. The other two chiefs crossed themselves.
“You can do this?” Trevisan demanded.
I suspected the Maestro could smell another thousand-ducat fee, maybe ten thousand. On the other hand, I did not think he would ever descend to witch hunting.
He sighed. “Alas, no. In my youth I might have essayed the effort, for it is a skill of the young. Now it would kill me. Fortunately my apprentice, sier Alfeo Zeno, here, is extraordinarily well attuned to pyrogenic forces. He has an astonishing natural talent for pyromancy. I believe I can guide him to…Of course the risks are bloodcurdling, so the final decision must be his alone.”
Every eye in the room fixed on me. As I had never heard of my natural talent in pyromancy before, I attempted to look modest and calmly courageous. What in Hades was the old rascal up to this time?
What exactly were these “bloodcurdling” risks?
“Let us get this straight,” Soranzo said. “You realize that you are still bound by your oath to give true witness in this inquiry, and you are stating that your apprentice has the power to identify any demons that may be wandering around the city?”
The Maestro waved a hand dismissively.
“Of course not! There are minor demons everywhere. Would you expect him to stand on the bell tower of San Marco and locate every cooking fire in the city? But if there happened to be a great building ablaze, then he should be able to locate that, surely? A major demon is a furnace of evil and this one has dared to meddle in my affairs. Alfeo is a
brave and resourceful lad, and with my guidance…I am merely saying that there are methods he may be able to use to identify a major demon within the city, and I do not know any man with greater skills in this field.”
I made a mental note to demand a substantial raise before it was too late. Meanwhile the chiefs had realized that they were on the point of contracting Maestro Nostradamus to perform magic for them.
“Then we urge you to continue your investigations,” Trevisan said hastily. “The Republic will be generous if you are successful. Remember how confidential this matter is.”
What he meant was, Go away and do it, but don’t tell us.
14
H aving seen the Maestro securely loaded on Bruno’s great shoulders, and retrieved my rapier from the fante who had confiscated it, I led the way out of the palace by the Frumento gate with no small sense of relief. Dusk was settling over the basin, where a dozen galleys lately returned from distant lands had been unloading cargo all day and now were falling silent. Giorgio was chatting with a dozen other gondoliers on the Molo, and waved when he saw us. In moments we were skimming over the waters of the Grand Canal, homeward bound and rid of both our uninvited guests.
The long day was over, I hoped-I had a date with Violetta. Yet I had not forgotten all the firewood that Bruno had taken into the atelier. Pyromancy? I knew nothing about pyromancy and would happily wait until tomorrow to learn. It was too hot for pyromancy, although sunset was painting blood on great clouds to the east, the first clouds I had seen in weeks. The heat might be going to break at last.
