Dougray Scott: Thomas Jericho
Tom Jericho : I like numbers, because with numbers, truth and beauty are the same thing.
Wigram : Were you surprised when you heard that Admiral Donitz had changed the weather code?
Tom Jericho : Well, the Germans were always nervous about Enigma. That was the reason Shark came on in the first place...
Wigram : But the Germans believe Enigma's supposed to be infallible, because it would take people a thousand years to figure out the settings for one day, and they are changed every day. But we don't use people for that, do we, Mr. Jericho?
Tom Jericho : No.
Wigram : No. And that is the secret inside the secret: your thinking machines. Day and night, clackety-clack, programmed with a menu provided by your amazing brain, narrowing down the infinite possibilities to just a few million. And if anyone tells the Germans about that... there goes the war.
Tom Jericho : Do you have any idea what you're talking about?
Skynner : Tom's been on sick leave for the last month, so I don't think he's fully...
Tom Jericho : Enigma is a very sophisticated enciphering machine, and Shark is its ultimate refinement. So... we're not talking about the Times crossword here.
Tom Jericho : Every day, our Typex machines have to be set the same way the Germans set their Enigmas. And figuring out the settings is the hard part. That's where the code breakers come in.
Hester Wallace : What would Claire need to decipher the settings?
Tom Jericho : She'd need a crib. Let's say this tombstone was in code. If I knew more or less who's buried here, I'd have a pretty good idea what the code meant. You try to work out the settings and then type the coded message into the Enigma machine. If the message comes out nonsense, the settings are wrong. If it comes out "Mary Jane Hawkins," you've broken Enigma for that day.
Tom Jericho : It weighs twenty-six pounds, battery included, and goes anywhere. The Enigma machine - the Germans have thousands of them.
Hammerbeck : What's it do?
Tom Jericho : It turns plain-text messages into gobbledygook. Then the gobbledygook is transmitted in Morse. At the other end is another Enigma machine, which translates the message back to the original text.
Hammerbeck : And you have one of your own.
Logie : Uh, courtesy of the Polish Cipher Bureau.
Hammerbeck : So what's the problem?
Tom Jericho : The problem? The problem is the machine has a hundred and fifty million, million, million ways of doing it, according to how you set these three rotors, and how you connect these plugs. Press the same key any number of times, it'll always come out different.
Hammerbeck : And that's Shark?
Tom Jericho : No. No, no, no, this is the one we can break. Shark is enciphered on a special Enigma machine with a fourth rotor, designed especially for U-Boats - which gives it about four thousand million, BILLION starting positions. And, uh, we've never seen one.
Hammerbeck : Holy shit...