The Low-Stakes Race to Crack an Encrypted German U-Boat Message

A ramshackle team of American scientists scrambled to decode the Nazi cipher before the time ran out. Luckily, they had a secret weapon.

On a balmy Saturday in July, at approximately 15:30 hours, the first signals come in over the radio receiver. Its faint dip dip dip is barely detectable as a small team of engineers and scientists scramble to their stations and listen, trying to decipher the message, delivered through Morse code. They have 72 hours and time is ticking. What was once an auxiliary room above a garage in suburban Maryland is now command central.

Dip dip dip, the code repeats, before fading once again, absorbed by a whoosh of static.

“Did anyone reach out to Los Alamos?” asks someone.

In what sounds like a scene ripped from the movie Oppenheimer, which coincidentally had its premiere the day before, is instead part of the Maritime Radio Historical Society’s Crypto Event. From their own radio station, KPH in Inverness, California, MRHS crypto coordinator Kevin McGrath is transmitting a message based on one sent 81 years ago, by Kapitänleutnant Hartwig Looks, commander of the German submarine U-264. That message was intercepted by the British destroyer HMS Hurricane in the North Atlantic in 1942.

Back then, however, the codebreakers in Bletchley Park were unable to decrypt U-boat radio traffic, due to the introduction of the newer and more complex four-rotor Enigma code machine, an upgrade from the three-rotor model. The “Looks Message,” as it has become known, remained unbroken until 2006 when a dedicated team of Enigma experts deciphered it using modern computers and advanced cryptographic techniques. 

Tim Koeth, a professor and nuclear physicist in the department of Materials Science and Engineering at the University of Maryland, just so happens to have an original three-rotor Enigma machine. Of the 145 participants in this year’s Crypto Transmission Event, Koeth is the only one using an Enigma machine. Now, if he can just get it to work before time runs out.

A primer: An Enigma is a device used by the German military command to encode strategic messages before and during WWII. From the outside, it looks a lot like a courtroom stenography machine. Inside is a whole other story, involving a complex system of letter keys and plugboards and rotors. The important thing—and what Koeth is trying to gather—is information about the starting position, the order of the three rotors, and how to position the plugs in the board. The whole system relies on the sender and receiver setting up the same pattern. If not, Koeth essentially will be decoding gibberish.

“I need total quiet,” he says, moving between two of the three radios he’s set up in preparation for the event. He adjusts some knobs and waits for another call sign from Inverness. In total, the message will be sent four times: twice in Morse code, twice in radio teletype.

Jim “Jimbo” Krutzler, an electrical engineer from Flemington, New Jersey, sits in front of the third radio, an open box of Snickerdoodles by his side. Krutzler and Koeth met as undergrads at Rutgers University, at an activity fair for the ham radio club. It’s also where Koeth met his wife, Michelle Koeth, who is downstairs entertaining around 50 guests who have shown up for the couple’s annual High Voltage Weekend. Later, partygoers will take turns standing inside a Faraday cage as a Tesla coil sparks before them like crazy.

“What am I supposed to see?” Krutzler asks, staring at his screen and bouncing his knee like he has a baby on it. His T-shirt reads “Defense Nuclear Weapons School.”

“You’re supposed to see a little ladder,” explains Koeth. “Like DNA strands.”

A few minutes go by before the transmission begins again. This time, it sounds a bit different. Koeth gives the thumbs up. Holly Wilson, a student of Koeth’s who graduated with a bachelor’s in physics in 2023, gets enlisted to transcribe the code into a yellow-lined legal pad. She’s wearing a faded Fleetwood Mac T-shirt and has a massive tattoo of an octopus wrapping her arm. Wilson writes down OKTOBER 7 and DBK WSE before the signal fades.

“That’s it, that’s it!” shouts Koeth. He consults the page from the German Army Staff Machine Key Number 28 book, provided by MRHS in a link on its website. He’ll need to obtain the key setting for the Enigma machine, the first step in decoding the message. The team has been at it for almost an hour.

At last, Koeth opens the wood cover of the Enigma. Although it’s possible to purchase one for between $300,000 to $500,000, Koeth received his as a loan from a collector in California, a WWII buff who has an exact replica of Little Boy, the atomic bomb dropped on Hiroshima, in his backyard. (Ensuing calls from concerned neighbors.)

Koeth’s own workplace might be cause for similar concern. A faculty member at UMD since 2009, his second-floor office holds an impressive collection of radiological antiquities such as Fiestaware, Vaseline glass, and, under lock and key, some Lone Ranger Atomic Bomb Rings, cereal prizes from the 1950s that contained a small amount of polonium 210.

Koeth removes two rotors from the machine, turns one to 6 and the other to 12, and plops them back inside.

“We gotta do the plugboard next,” Koeth announces before closing the lid. He begins to plug and unplug a series of tubes in a way that recalls Ernestine, Lily Tomlin’s immortal phone operator.

“No wonder the Germans lost the war,” says Larry Westrick, an electrical engineer from Opelika, Alabama. “It takes too long to communicate.”

Luckily, tenacity is part of Koeth’s job description. When he was 10, Koeth laid out plans to build a nuclear reactor in his parents’ basement in Piscataway, New Jersey.

Next, entering the code in cyphertext, Koeth pushes some of Enigma’s buttons, which in turn moves the rotors like the inner workings of a clock; a lampboard lights up a corresponding letter in plaintext. “It’s a guessing game,” he says, turning quiet. “Just think,” he says after a while, “they had to do this every day.”

Krutzler, Westrick, and a few newcomers gather around Koeth and his machine. There are 100 letters in the message and so far, none of them seem to make any sense.

“Something is wrong,” they say in unison. A joke goes around that the secret message is “Drink more Ovaltine.”

Koeth refers to a set of instructions. “Basically, you key in the first set of letters, and they should match the second set of letters. Which they don’t.”

The room is stifling, and Koeth, who proposed to Michelle by tapping “Will you marry me” in Morse code on her knee (“He always wanted to propose like Thomas Edison did.”), appears stymied.

Koeth: “They had Enigma school back then.”

Krutzler: “They had nicotine back then.”

The group finally decides to review the procedures once again, unsure they are reading the Army’s daily key settings correctly. Like the last line in an optometrist’s eye chart, one of the letters might be “R.” Or it might be “P.” It’s a sticking point, this fuzzy letter.

“The Germans wouldn’t do that to us, would they?” cracks Koeth.

Eventually, even codebreakers have to eat. Michelle Koeth calls for dinner and the team reassembles in the kitchen for deli sandwiches and microbrews. When the sun sets, the party—which includes a randy bunch of Koeth’s students, curious neighbors, a few high school teachers, a lanky surplus dealer, and a retired FBI agent—moves outdoors for some high-voltage demonstrations.

For this year’s 25th annual gathering, someone will shoot a metal ring through the center of a pulsed magnetic coil, sending it up into the skyline before returning to Earth and nearly missing Raven, the Koeths’ standard poodle. Another, using a Styrofoam cup, will replicate the pressure experienced by the submersible on its tragic voyage to the Titanic. (The cup, instead of being flattened, is miniaturized.) The grand finale is a turn in front of the Tesla coil.

Early the next morning, a master codebreaker arrives in the form of Koeth’s PhD student Noah Hoppis. It’s the first day he’s allowed out of Covid quarantine. It’s he who will figure out that the fuzzy letter is an “I.” Later, Kevin McGrath will email Koeth a clean recording of the message. He and Hoppis will work late into the night, and at 01:04 hours on Monday morning, they will correctly decode the message as:

DONITZ FROM LOOKS 

FORCED TO SUBMERGE DURING ATTACK X DEPTH CHARGES X
LAST ENEMY POSITION GRID AJ NINE EIGHT SIX THREE X
I AM FOLLOWING X

Instead of saving the world, they will receive a certificate from the Maritime Radio Historical Society. And the glory of a job well done. “I was obsessed,” says Koeth, before heading off to bed.

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