Wednesday, December 12, 2018

The SAR-Tech Sinnet | Easy Paracord Access

7 minutes into his What's in my 24 Hour SAR pack, Ephraim pulls out an impressively spooled length of florescent paracord. He explains that it's wrapped using the SAR Tech Sinnet method. The name, he explains, comes from the fact that this method of paracord storage is preferred by Canadian Armed Forces Search and Rescue technicians. Got to love those Canadians; even their paracord is polite.

A search for SAR-Tech Sinnet turned up this YouTube video which shows how to create the bundle. Further research shows that the rest of the world knows this method of storage as creating a paracord donut.

Regardless of what it's called, it's obviously handy and I'm amazed I haven't come across it before. Once the SAR-Tech Sinnet is created, it's trivial to spool off controlled lengths of paracord without it knotting. The donut itself can serve as a weight, which helps when tossing a length of paracord . Learning to create the sinnet takes only a few minutes, and involves little more than repeating a trivial pattern. The only downside seems to be that it's not an especially fast way to bundle cordage. However, I'll gladly put in 15 minutes of prep-work at home, to avoid 10 minutes of wrestling with a knotted hunk of rope in the cold and dark.

Here's a 25 foot sinnet I created in about 10 minutes:

If you've got lengths of rope lying around, you really have to give this technique a try.

Tuesday, December 11, 2018

The Algorithm That Saved the Union | Civil War Encryption

OK, maybe that title is a bit click-bait'y. But it's true that the algorithm that powered the North's encryption during the US Civil War no doubt had a significant impact on the outcome of the war. At the core of this algorithm was the use of a route cipher. This cipher is brilliant in its simplicity.

Start with a grid of spaces and a non-obvious route to visit each cell in the grid:

Fill grid with your message, putting one word per cell.

To encrypt the message, traverse the prescribed route, writing down each word as it is encountered:

Note the delightfully jumbled message.

To decode the message, traverse the route again, filling in words as you move from cell to cell. When the grid is fully traversed, the original message will be restored in the grid and can be read as clear text.

The Union Army strengthened this basic cipher with a number of enhancements:

  • Critical words were exchanged with code words. For example, any time the word enemy was to be used wiley was substituted.
  • Each route had a corresponding keyword that itself was included in the message. This allowed lengthy messages to be encrypted using a variety of routes, with the results being concatenated together.
  • Nonsense words could be added in the first and last row of the grid. This resulted in noise being mixed into with the message. When decrypted, the meaningless words were easy to discard.

You can see all these features at work in the example from the article Internal Struggle: The Civil War. The screenshots below show my coding of the routes, dictionary, clear text and coded message.

My implementation of the Union Cypher is on the clunky side. For one thing, I wanted to support more complex routes than simply walking up and down columns. The staton and mcdowell routes for example, call for traversing diagonally from the bottom left hand corner to the top right hand, and then proceeding column-wise. To support this, I describe routes by numbering each cell in the order they are to be visited. This makes for tedious route definition, but it is also quite flexible. You could imagine routes that had a checkerboard shape or other unusual patterns. I've also explicitly included the rows that will contain nonsense words in the grid.

These programming complications are great examples of steps in an algorithm that a human can trivially process but a machine needs to explicitly account for.

Just as interesting as the use of the cypher is the context within which it developed. The Civil War posed a unique military challenge:

The contending forces spoke the same language, shared the same social institutions, including an un-muzzled press and a tendency to express oneself freely on any subject. Military knowledge was shared in common--former classmates at the service academies and peacetime friends would meet in battle. They knew each other’s strengths and weaknesses, and they eagerly devoured reports, in the press and through intelligence sources, of the names of opposing commanders. Each harbored sympathizers with the other side, the basis for espionage and a potential fifth column. Neither inherited any competence in information security nor an appreciation for operational security. Those things would be learned the hard way--the American way--accompanied by bloodshed.

While the Union and Confederacy started from the same point, they made technological choices that ultimately drove how successful they would be in the world of information security. For example, the North's choice of word jumbling over a letter based cypher would have profound impact:

In the North, as telegraphers (frequently little more than teenage boys) were pressed into service and formed into the U.S. Military Telegraph (USMT), a rival of Myer’s signal corps, a word, or route, transposition system was adopted and became widespread. It gave the telegraphers recognizable words, an asset in this early stage of copying Morse “by ear,” that helped to reduce garbles. Code names or code words replaced sensitive plain text before it was transposed, and nulls disrupted the sense of the underlying message. Only USMT telegraphers were permitted to hold the system, thereby becoming cipher clerks as well as communicators for their principals, and the entire organization was rigidly controlled personally by the secretary of war. In the War Department telegraph office near the secretary, President Lincoln was a frequent figure from the nearby White House, anxiously hovering over the young operators as they went about their work.

In the South, although a Confederate States Military Telegraph was organized (in European fashion, under the Postmaster General), it was limited to supplementing the commercial telegraph lines. (“System” would not convey the proper idea, for the Southern lines were in reality a number of independent operations, some recently cut off from their northern ties by the division of the nation and reorganized as Southern companies.) Throughout the war, the Confederate government paid for the transmission of its official telegrams over commercial lines. Initially the Southern operator found peculiar digital texts coming his way (the dictionary system), then scrambled, meaningless letters, begging to be garbled. The poly-alphabetical cipher used for official cryptograms offered none of the easily recognizable words that provided a crutch for his Northern brother.

This is an interesting example of how an apparently less secure system (one where words are kept intact) can ultimately prove to be more valuable than a seemingly more secure one. Or, put another way: never underestimate the impact of human error.

Sunday, December 09, 2018

Puerto Rico Adventure - Day 7 - The Last Day

[Composed 11/26/2018]

When we awoke this morning we knew that by the end of the day we'd be getting on an airplane with its destination being a frigid Washington, DC. This alone motivated me to try to pack as many mini-adventures as possible into the day.

We started off with a tour through the Jardin Botanico UPR - Rio Piedras. The garden wasn't the largest or flashiest we'd ever been to. But was a wonderful way to get a walk in a natural setting without having to drive a significant distance. We saw a handful of interesting birds and flowers and generally enjoyed soaking up our last day of perfect Puerto Rican weather. Combine this with free-admission, and I'd rank this as a worthy place to visit should you find yourself in San Juan. On our way out, we asked about the orchids. The guide explained that Maria had decimated them and there were no longer any to be found in the park. Apparently the garden had taken quite a beating and the orchids were only one of the many victims. This was theme for us throughout our week in Puerto Rico: to the untrained eye, hurricane Maria had hadn't left much of a mark. But dig a little deeper and it seems like every aspect of Puerto Rican life was impacted by this hurricane, and there's still much left for the island to recover from.

After the gardens, we made our way to Plaza del Marcado de Rio Piedras. Like the botanic gardens, this market isn't anywhere near as epic as ones we've visited in Morocco or Japan. Still, it was was a fun market to walk through, and had we needed to pick up any cheap supplies this would have arguably been the place to do it.

We ate lunch at Fela's vegetarian restaurant, which was quite delicious. They offered quite an extensive set of veggie options, allowing us to create quite the veggie friendly smorgasbord.

We spent our final few hours in San Juan by wandering the Plaza Las Americas, which has the distinction of being the largest shopping mall in the Caribbean. When it opened, it was the largest shopping mall in Latin America. Yeah, it's big. But mostly, it felt like stepping back in time. What with Sears and JC Penney being anchor stores, and walking by a Time-Out Arcade.

After the mall, we fought traffic to get to the airport, where we boarded for an on-time departure.

We really can't recommend Puerto Rico highly enough. It's got everything we look for in a destination: hiking, history and lots of opportunity for adventure, and welcoming natives. The casinos don't hurt either.

Puerto Rico - Day 6 - Secret Beaches and Shira's Retirement Plan

[Composed 11/25/2018]

A day at the beach is OK. A day at a hidden beach, with a mile hike through a forest to get there, now that's what I'm talking about! Technically, the hidden beach we were exploring wasn't so hidden. The Frommer's Guidebook explains in detail how to get there. Essentially, you walk to the end of Seven Seas Beach, where you find a trail that disappears into a forest. You take that trail and a mile or so later, you pop-out on a stretch of coastline which provides miles of secluded beach access.

Perhaps the best feature of the beach wasn't the beach itself, but the forest it's adjacent to. This provides for shady areas to rest in, just a few feet from the crystal clear waters. After an hour of walking, we found a nice spot and setup for lunch. On a whim, we picked up a can of sterno at the supermarket and brought it with us to the beach. We found 3 remains of coconuts nearby, placed them tightly around the lit sterno can. We then rested a foil packet containing hot dogs on the coconuts and waited for 15 minutes (flipping the foil packet every 5 minutes). The result: perfectly cooked beach hot dogs! With the waves lapping at the beach, the perfect scenery and the delicious hot dogs, it was just about the perfect lunch.

After lunch we walked back towards the Seven Seas beach looking for a place to splash around in the water. As we walked, we passed a number of groups that were enjoying the quiet stretch of coast as much as we were. At least two parties were truly taking advantage of the solitude, by swimming sans-bathing suits. One group was a couple, which I suppose I can appreciate (who wouldn't want to skinny dip with their significant other?). But the other was a larger group of individuals. I just can't imagine how that conversation goes down: Shira and I hitting are the beach this weekend, anyone else up for some nude swimming?. What can I say, my puritan roots are showing.

The only area the beach didn't live up to was the claim that it was an ideal for snorkeling. I tried my hand at snorkeling in a few different spots and saw nothing. Perhaps I needed to swim out further?

After our day at the beach, and a trip to the hotel hot-tub, we went out for a delicious Mediterranean dinner and then hit up the casino. I continue to be amazed at how fluidly the dealers switch from Spanish to English, especially at the blackjack table where it means switching languages depending on the player you're dealing to. What remained consistent from other casinos we've been to is vibe of the blackjack vs. craps tables. Blackjack tends to be filled with new 'kids,' every night; whereas craps was the same old guys playing night after night. If we wanted to feel old, we need only stop by the blackjack table. If we wanted to feel spry, that just took hanging out at the craps table.

Friday, December 07, 2018

Reflective Body Armor. For my running fanny pack.

I picked up a few yards of reflective elastic a couple of weeks ago. While on a night time run, it occurred to me how I could put some of it to use: as a sleeve for my running fanny pack. I figure adding a passive way to be seen at night would pair well with my active measures.

The project was easy enough to do: I split the sleeve into two lengths and attached backing fabric to each. The result were channels I could slide each end of the waist belt through.

If anything, the sleeves are too good a fit. I was expecting to be able to add and remove the reflective cover as needed, but it's tight enough that doing so is a hassle. Ultimately, the tight fit may serve me well.

For now, I'm safety-pinning the two sleeves together, though I have plans to to attach them with Velcro or another fastener. I figure better to get a few test runs in with the setup than commit to an approach now.


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