The ultraviolet is equally distracting. It makes my fingernails seem luminous. I wave it over objects that take my fancy, and discover the hidden watermarks and security devices in my chequebook and passport. There are hidden phosphor bands on stamps, and images and tiny flecks of specially dyed paper in banknotes, invisible to the eye in ordinary light. Shining as if white-hot in the darkened room, they seem strangely beautiful. I also look at the postcard with it, and am disappointed to find there’s no hidden message.
It’s Saturday evening. I’m alone, and feel alone. As night falls, the familiar beast of despair begins to creep up on me. I have no tobacco and am too lazy to go and buy any. Worse, there’s virtually nothing to drink but a final bottle of Chateau Batailley, which I’ve promised myself I’ll save for a special occasion. This calls for a difficult decision. It’s either the Batailley or the sole other source of alcohol in the house: roughly half a bottle of Armenian cognac, which a so-called friend has palmed off on me as a gift. It’s so bad I haven’t touched it for six months, having discovered what damage it can do to the untrained nervous system. I retrieve it from the back of a kitchen cupboard, mix a slug with some mineral water and discover to my surprise that it’s quite drinkable. I also find a cigar, which I’ve similarly promised myself to save for a special occasion. I light the cigar, dig out my topographic maps of Afghanistan, and return to the cognac.
At ten o’clock I lurch into the grey morning with a sharp pain in my head where the cognac has etched Category 2 damage in the region of my cerebellum. The house reeks of cigar smoke, so I throw open the windows and put the coffee percolator to work in the kitchen. Taking the first sip, I hear myself whisper, ‘I must not do this again,’ and wonder how often I’ve uttered the same words. My Afghan maps are scattered on the floor by the sofa where I’ve fallen asleep. As I’m gathering them up there’s a triple knock at the door. I flee upstairs, throw on some clothes and return to the door.
The daylight is painfully bright. In front of me stands a clean-shaven middle-aged man with a sheaf of paperwork in his hand, and for a terrible moment I think of all the letters from the Television Licensing Authority which I’ve thrown away unopened.
‘Good morning, sir. I hope I’m not disturbing you.’
I don’t like the ‘sir’ part. It makes him sound like a policeman. But he doesn’t look like one. He’s wearing a black suit like an undertaker’s, for which he’s grown slightly too big, and a tie with green and red diagonals that hurts to look at.
‘Of course not,’ I reply with an unconvincing smile.
‘I wonder if I can ask whether you read the Bible?’ he asks. Resting in the crook of his arm like Moses in a basket is a sheaf of denominational literature.
‘I do, as a matter of fact.’
A smile of pleasant surprise spreads across his face, but it’s not a morning to give the enemy too much room for manoeuvre, because I don’t do religion on a hangover.
‘I also read the Qur’an. I have a soft spot for Marcus Aurelius too, and he was a pagan.’
The smile fades. He’s not really expecting this and a slight stutter comes into his voice. ‘But… but do you believe your actions in this life make a difference in the world to come?’
‘If we’re going to be judged on something in an afterlife, I think it’ll probably be our inactions. It’s not difficult to live a pious life, if you think about it, imagining you’ll be saved if you stick to a few rules. But think of all the good things you could have done but didn’t because you were too lazy or complacent. I think we’ll be judged on our potential.’
He’s frowning now.
‘I forget where I first heard the idea, but it does stay with you. I think it’s somewhere in the Qur’an.’
I pluck a copy of the Watchtower from his grasp and thank him warmly, saying I hope I’ll see him again soon. The speed at which he walks away up the drive suggests I won’t.
With a feeling of guilty victory I return to my coffee. Then I close the windows in the sitting room because the light is hurting my eyes, and sit down at the table, taking the postcard from the mantelpiece where I left it. I read it again several times. There’s nothing out of the ordinary about the text. I wonder if the picture, depicting a nomad leading a line of camels, is intended to convey a meaning. It’s the identity of ‘Mohammed’ that bothers me. I wonder if it might be worth looking through my diaries from the period I was last in Kabul, but if the card was sent months earlier, whoever Mohammed is will have given up hearing from me.
I take the card to the kitchen and boil the kettle, hold the card in the steam and gently work a corner of the stamp with the tip of a knife. I’m not sure what to expect – anything strange or out of the ordinary.
As the stamp begins to curl back in the steam, what I see is even stranger. Under the stamp, in the same ink as the writing on the card, is a tiny drawing of a dinosaur with a smiling face.
It’s a stegosaurus.
Cryptography is the science of hiding the true meaning of a message by disguising it; encrypting it by some means known to the recipient but not to others. As long as the sender and the recipient keep their means of encryption secret, the effort needed by the codebreaker is determined by the difficulty of the code. Some codes, like alphabetical substitutions, are easy to crack because the frequencies at which letters appear in words are well known. Others, like one-time pads based on random numbers, can only be cracked by computers, if at all. The most complex codes that use block ciphers and multiple algorithms need both computers and time, and modern computing power means that few codes are truly impossible to crack, given enough of the latter. But the science of hiding a message by disguising it as something which on the surface appears innocent is called steganography.
Strictly speaking, a message written in invisible ink across an ordinary letter is an example of steganography: the visible or cover message is innocuous. It’s an ancient idea. Herodotus describes a king who tattooed a secret message on the shaven head of his slave, whose hair was allowed to grow before he travelled through enemy territory to deliver it. More recent applications allow secret text to be hidden in the data of digitised photographs sent over the Internet. The advantage of a steganographic message is that, unlike a coded message, the secret part doesn’t attract attention to itself. It resembles something ordinary, and hides itself thereby.
My ex-wife, come to think of it, has a steganographic personality: an innocent-looking face concealing a cruel agenda.
I decide it has to be the numbers: thirteen and forty. ‘Degrees’ in the cover message also seems to be an overt clue. I find an atlas and look up the latitude and longitude. Problem. Thirteen degrees north and forty degrees east puts me in the mountains of northern Ethiopia. Forty degrees west is equally challenging – somewhere in the mid-Atlantic trench. Southern readings for the latitude land me in thick rainforest in Mozambique and Brazil. The numbers are not an obvious location.
They’re too short to be a phone number or a postcode. The only other reference I can imagine they might give is a book code, indicating a page and line number in a book known to both sender and recipient. But I haven’t agreed on a book with anyone called Mohammed.
Then it hits me like a delayed reaction, as I hear the echo of my very own words: I also read the Qur’an. The ‘old friend’, Mohammed, is the clue. It’s so obvious I can’t believe it’s taken me so long to realise. Now I regret my uncivil behaviour towards my visitor.
For centuries the mas-haf code, virtually unknown in the West, has been used in the Islamic world to encrypt messages using the numbers of the Qur’an’s sacred verses. Being identical in every version of the text, irrespective of country or date of publication, the verses retain the same numbers and provide thereby an unchanging key.