Dress code: How a Winnipeg codebreaker cracked one of the 'world's top unsolved messages'

"Bismark Omit leafage buck bank."

That seemingly random string of words appears in something called the Silk Dress cryptogram, 23 handwritten lines on twosheets of crinkled paper that were discoveredin a hidden pocket of a Victorian-era dress bought in Maine in 2013.

The lines seemed like an encodedmessage from the late 1800s, withreferences to North American cities, includingCalgary and Winnipeg.

"There were lots of theories [about its meaning], from the American Civil War to simply instructions for dress-making," said Wayne Chan, a University of Manitoba computer research analyst.

For about a decade, it stumpedthe global cryptanalytic community and was even listed as one of the "World's top 50 unsolved encrypted messages" on the cryptology blog Cipherbrain.

Chan says he was drawn to the mystery. "Why did this woman have a bunch of secret codes in this pocket in her dress?"

He cracked it in February, and his conclusions were publishedin the cryptology journal Cryptologia.

A dress with a secret

The mystery of the Silk Dress cryptogram starts in2013 in Searsport, Maine, when dress collector Sara Rivers-Cofielddecided to buy along, flowing 1880s-era silk bustle dress she had been eyeing at an antique mall.

"I knew it had been there for a while," she told CBC."I brought it home with my mom and it was sort of the newest big-deal acquisition for my collection."

When theyexamined the dress to figure out how it was put together, Rivers-Cofield and her mother found twopieces of crumpledpaper concealed in a secret pocket under the overskirt.

"It's a bit of a private spot it almost seems like it was protected," she explained. "It said 'Bismark Omit leafage buck bank.' It was just nonsense.So we were like, what'sgoing on?"

She put iton a dress collecting blog she ran at the time.

"It's certainly the most popular blog post I ever did, because the code-cracking community picked up on it pretty quickly," she said."Somebody said, 'That's a telegraph code.'"

Still, it would take nearly a decade for someone to solve it.

Cracking the code

Telegraph codesare all but forgotten today, but in the late 1800s, they were ubiquitous as the telegraph became the predominant means of rapid long-distance communication.

Thousands of codes weredeveloped thatalloweda word,a phraseor a sentence to be represented by a single code word.

It didn't just makemessages shorter and cheaper to send, it wasalsosecure.Unless you had the right code, the messages would simply appear as a random string of words, even as they passed through many hands.

WATCH | How this135-year-old mysterious message was finally cracked:

Canadian codebreaker cracks 135-year-old mystery message

9 months ago

Duration 2:21

A cryptic message hidden inside an antique silk dress stumped codebreakers for years, becoming one of the world's top unsolved messages. Then, a Canadian finally broke the code and learned what it says.

Chan said that when he started looking into the Silk Dress cryptogram, "I went through 170 code books and I ended up not finding anything that matched this."

The key was to nail down when the messagewaswritten.The dress was a big clue.

Rivers-Cofield was confident from the machine stitching, buttons and overallstyle of the dress that it dated to the 1880s.ThathelpedChan narrow his search to a specific time, but he still ended up hitting dead ends afterlooking through dozens of Canadian and American university archives.

"I thought, I needto immerse myself in the era of the telegraph more, I need to understand how it was used," he explained.

Whatstruck Chan was how the style and structure of the Silk Dress cryptogram resembled weather messages he found in his research typically lines of five to seven words that began with a non-encoded word as a locator.

That led him to call thearchives of the National Oceanic and Atmospheric Administration (NOAA) in Washington,D.C., wherea copy of the 1892 U.S. Signals Service Weather Codeconfirmed his theory.

"I could tell it was clearly the right code it didn't match exactly but about 90 per centof it fit," Chan said.

A little more research led him to an 1887 version of the signals code that matched.

A cold spring day

Turns out "Bismark Omit leafage buck bank" was a weather observation for May 27, 1888, in what is todayBismarck, N.D.

The way the U.S. Signal Service Weather Code worked waseach word in eachlinecorresponded to either a location ora set of observableconditions.

When a weather reading was taken, it would be matched to a predetermined word in the codebook, and that word would be transmitted.

In the Silk Dress cryptogram, the first words of each line weren't encoded, soBismark was the locator for the weather station.

The second word,Omit, corresponded to an air temperature of 56 F and abarometric pressure of 0.08 hg.

"Leafage"meant the dew point was 32 F at 10 p.m. "Buck"describedclear skies, no precipitation and a northwind. "Bank" meant wind velocity of 12 mph.

Cross-referencing amap of telegraph routes, Chan believes these were daily observations relayed from far-flung weather stations down thelineto Washington, where the U.S. Army Signals Serviceproduced daily national weather reports.

"For the first time, the telegraph allowed news about the weather to travel faster than the weather itself," Chan said.

At the time, the U.S. and Canadian governmentshad an agreementto exchange weather information by telegraph.

That's how names of Canadian cities got intothe Silk Dress cryptogram.

It includes observations fromstations in Calgary, Minnedosa, Man., Winnipegand Prince Arthur's Landing modern-day Thunder Bay, Ont. which all shared a telegraph line that connected to Milwaukee, Wis.,and routed messages to Washington through New York.

This line described a cool spring day at the Fort Garry weather station in Winnipeg:

"Garry Noun Tertallawful palm novice event."

According to the code, Garry listedthe weather station. "Noun" wasthe day of the month, the 27th. "Tertal"was 42 F, with barometric pressure 0.94 hg. "Lawful" was humidity of 30 per cent at 10 p.m. "Novice" meantstratus clouds with 8/10ths cover. "Event" meantcloudy with wind velocity of 0-4 mph. The word "Palm" doesn't appear in the code;Chan believesit wound up in the message by mistake.

Calgary, meanwhile, was a little cooler that day, 40 F(4 C) and clear, while Thunder Bay was 46F (7 C), as anortheast wind blew on Lake Superior.

Sonotexactly classified information.

Code cracked but mystery remains

Who owned the dress, and why was a seemingly benignmessageconcealed for more than a century in a secret pocket?

That part of the mystery still eats away at Chan.

"My best guess is it is a woman who worked for the Signals Service office in Washington," he said.

The explanation could beas mundane as someone forgetting abouta piece of paper left inher pocket at the end of the day, and by chance the dress was packed away, the message long forgotten.

"Were they just pieces of scrap paper?" Chan wondered.

The dress does offer a possible hint:alabel that reads "Bennett."But Chan found no record of a Bennett employed at the Signals Service in Washington at that time.

Rivers-Cofield, who isalso an archeologist, is equally fascinated and perplexed by the history here.

"I'm sure it would be much more fascinating, and blow up in a much bigger way, if it was a secret code to do with some war or spy or whatever," she said.

She points out that at the very least, the mystery offers insight into the time.

"Honestly, I feel like it's much more eye-opening to think about what knowing the weather meant to people ... for the first time."

Chan, meanwhile, isn't giving up yet.He says he still has a few avenues to pursue that may help crack the dress owner's identity.