“Sure. How do you take it?”

“Julie Andrews,” she replied. Seeing the look on his face, she elaborated. “White, none.”

He stared at her blankly, then shook his head and made to leave.

“And something to eat!” she shouted after him. Anything to buy some time!

Using the interactive pen that slid out of the front edge of the computer, she scanned the first line of symbols from the printout Patterson had given her, and pretended to study the output until she was sure he had gone.

She tilted her head to one side to check for noise from the corridor. Hearing none, she browsed her saved images and found an appropriately-sized photo of some engravings from the Sixth Pylon at Karnak: the texture of the stone and lighting were similar to that of the Library. She tapped an on-screen menu and accessed the application’s ‘about’ pop-up, before holding down a special combination of keys to open a small text-input screen.

It took her less than a minute to write the message, a little under one hundred characters. She knew that any more would be pushing it; she would only get one shot at this, and the smaller the message the easier it would be to hide.

She had known for a while that her tablet would be her best bet of contacting someone on the outside. Her first problem had been getting hold of it; something the events on Mars had precipitated.

The next problem was working out what to say so that George could find her, when she didn’t even know where she was to start with. For that, however, she’d had a stroke of luck.

Barely an hour earlier she had glimpsed the logos of NASA and DEFCOMM in the large hanger, before Patterson had slammed the door closed. She knew that they weren’t at NASA, so DEFCOMM were obviously the culprits, working in partnership with the unwitting space agency.

Later, in the control room, Patterson had let slip another vital clue: that they controlled the satellites and receiver arrays because they built them. It didn’t take a rocket scientist, and from what she’d seen this place had enough of them, to work out that DEFCOMM probably stood for Defence Communications. After what he had told her in the control room, it seemed odd that DEFCOMM should advertise its allegiance to NASA and the USA. But then, what better smokescreen? DEFCOMM was a very American company building American satellites for a government agency, for an American-led first mission to Mars. Who would guess they had their own, hidden, agenda? What scared her more than anything else she had seen was that Seth Mallus had some crazy ideas coupled with huge resources; a dangerous combination. If someone who built rockets, satellites, and who knows what weaponry could be so fanatical about some ancient Egyptian texts, then God help them all.

And, thanks to poor Mamdouh and the Wizard of Oz man, she knew that she was definitely in Florida.

With all of this in mind, she barely thought twice about what to write to George.

Her next task was how to hide the message.

When George had first developed the application, he had embedded some basic cryptographic algorithms so that he could send secret love letters to her. Every now and then, he would create a message on his laptop and send it to her to decode.

Now it wasn’t for fun: lives depended on it.

There were basically two types of cryptography: overt, in which it’s clear you’re looking at a code, but you’re damned if you know what it means, and covert, in which you have no idea you’re looking at a code.

The drawback of overt cryptographies is that once people knew you’re hiding something, you have to make it pretty much impenetrable. As a result, some overt encryption techniques are so complex, and require so much to be understood by writer and reader, that they aren’t worth the bother for simple love letters.

George had toyed with the one-time cipher, the only truly ‘unbreakable’ overt code. It involved replacing the letters of the alphabet with numerical values, which would give you a long list of numbers representing your message. These would then be dropped into a completely random string of numbers, which would be used only once. The next code would use a different random string. While the principle of the one-time cipher was sound, it was generally considered to be too much hassle; the random string of numbers had to be shared between sender and recipient, as well as the numerical values and their letter counterparts used to encode the original message.

Because such a cypher was generally deemed unbreakable, the hassle of encrypting was reduced by recycling the random string of numbers between messages, rather than always using new ones. As soon as the one-time cypher became the ‘more than one-time’ cypher, the code was broken.

So for ease of use, he had chosen to build covert ciphers into her translation program. The overwhelming benefit of covert cryptography being that if people didn’t realise something was hidden, you didn’t need to make such an effort to make it impenetrable.

Covert cryptography, or steganography, involved hiding a message inside a picture, in this case a scan of hieroglyphic text from Karnak. By using the encryption tool, a text-based message would be added to the colour components of the image file: each binary digit, or bit of the encoded message, was taken and added on to the end of the binary code for each individual picture element, or pixel. Adding a one or a nought to a pixel may change the shade of grey slightly, but overall the picture would remain unchanged.

The more code-bits you tried to hide in a picture, the more degraded the original image would appear; as soon as the image became too distorted from the original, the message would become less ‘covert’.

Using a specific decryption tool, which would ask for a shared keyword between sender and recipient, the code-bits would be extracted from the image, and the code decrypted for viewing.

Gail made sure the message was as short as possible by deleting a couple of unnecessary words. Satisfied with what she had written, she entered her keyword, and tapped to submit.

Seconds later, the image was ready, her secret message hidden deep inside each individual pixel, undetectable to the human eye and, she hoped, invisible to firewalls. If anyone suspected that there was a hidden message, it wouldn’t take them long to break her code; George had used an algorithm readily available on the Internet, and advanced code-breaking programs could unlock keywords within hours. But that was the beauty of George’s program: no one need ever know they were exchanging messages, because all you ever saw were pictures.

Now all she needed to worry about was how to send it to him. She leant back in her chair and stared into the screen. The network icon advised her that there were access points in range, but they were all encrypted. The irony didn’t escape her.

All the terminals she’d seen in the facility had thumbprint access restriction. No doubt, if they were as security conscious as she believed they should be, the thumbprint scanners would also take a minute sample of tissue to perform a quick DNA analysis. There would probably even be retinal scan software, using the cameras that were embedded into most screens. To back all that up, they might even ask users for a typed password before unlocking the displays, too.

So she wasn’t going to get a connection, and she wasn’t going to be able to log onto someone else’s machine. Despite all the technology she had used to get to this point, it was all going to let her down on the last leg. She had been so caught up in writing the message and hiding it that getting the message to him hadn’t even crossed her mind.

She hit the table in frustration. All I want to do is send a bloody email! As the word entered her mind, she froze. Mail! Tapping the screen quickly, she moved the image file to her memory card and closed the application. She then popped a small flap open and pulled out the thumbnail-sized piece of plastic.