Hiding in Plain Sight September 22, 2000

One of the oldest traditions at CalTech is Senior Ditch Day. Jealous underclassman took the opportunity to 'modify' the senior's room (i.e. moving furniture around, moving it outside, gluing it to the ceiling). To prevent this, the seniors would stack their rooms with concrete blocks, 2 X 4's, etc. to prevent entry.

Over the years, this evolved into a major production, with a variety of rules. Seniors would plan their stack for years before hand. One type was the brute force stack, in which the senior would use pretty extravagant means to block the doors and windows. And the underclassman could use any brute force attack to open it, as long as any damage done to the room was not permanent and could be fixed in 24 hours. Simply stacking concrete blocks would not do. A sledge hammer would break those down pretty fast. If the underclassman could get in before the seniors returned, they could do whatever prank they had planned.

One of the best and most expensive brute force stacks took place while I was there. A 12x12 railroad tie was dropped down to hold the door shut. This railroad tie also held up a complex arrangement of concrete, rebar, sheet metal, nails, and wood across the window, making it very difficult to use one type of saw or torch to get in. The window blocker was almost 3 feet thick. Since there was limited time to get inside, a brute force stack worked best by simply making it too time consuming to get in.

Now this senior had planned for everything, including the underclassmen coming through the walls. He had blocked entry through the adjoining rooms, even going to far as to place a stack on the sink fixture so that it could not be pushed up from below. However, his mistake was not realizing that the sink actually dropped down. So the underclassmen, cut a hole through the wall under the sink and lowered the sink. They got into the room inside of 1 hour and did a great job on the room.

Well, the senior was not happy. He had spent several thousand dollars on his stack and it had failed. So he tried again. Yes, this senior came back the next year through a technicality. (All engineers and pretty much everyone else except biologists had to pass AMA95- now called ACM95. He always seemed to fail the 3rd term, the time when Ditch Day occurred.He'd take a leave of absence from his job - TRW, I believe. Techers can be really strange people.). So he came back for 3rd term the next year and did another Ditch Day.

This time he really stacked everything. There was no way to get in without destroying the walls, or door. The window stack was even more elaborate than the year before. The 'senior' was pretty confident that no one would even try to get in. Little did he know that there was an underclassman who had been planning the entire year for his assault on the stack.

On Ditch day, this student and his team attacked the window stack. They had titanium drills, and acetylene torches and high powered saws and sledge hammers. I think they had shaped charges if need be. They spent the whole day attacking each layer of the window stack. Finally, 30 minutes before the return of the seniors, they opened up a small hole that our smallest freshman could squeeze through. He opened the stack from the inside and we were able to have our revenge. We altered the opening mechanism the senior had set up (Remember, he had to get in somehow), and replaced the window stack.

When the senior arrived, he thought he had beaten us. He smiled, acted superior and activated his opening mechanism. Total panic entered his face when the door refused to open. As we stifled laughter, he was rushing off to the phone to rent some demolition equipment. One of my better memories.

Now, brute force stacks died out because they were very expensive and took a lot ot time to develop. Also, just about anyone could brute force their way in. Most of us did finesse stacks. You often had to solve a series of puzzles to get the key to open the room. No one could enter unless they followed the rules of the stack. One of the best my senior year was done by an electrical engineer. He simply left a computer terminal outside his room with the words "Leave Me Alone" on it. It also had a really great adventure game to lead people on a merry chase. Everyone spent the whole day playing this great game, hoping that it would lead them to the code. To get in, all they had to do was ... not touch the computer or the room for 30 minutes. Leave everything in peace and the door would open. Of course, by playing the game, everyone kept resetting the clock. Pretty cool. And a keen insight into human behavior.

I was not so creative. I just made my finesse puzzle complex. I wrote the message giving the details of opening the door in a simple substitution code and put it on the back of a completed jigsaw puzzle. I left the disassembled puzzle outside. All they'd have to do is put the puzzle together and they'd have the message. Unfortunately for them, the puzzle was a single color, blue, making it very difficult to put the puzzle together. I put the solution to the code on a cassette tape within reach from the window. It was hidden amongst a lot of other items.

Hard work would put the puzzle together. Not elegant but it gave them something to do. But they would need the correct substitution code to easily read the message. The interesting thing was that they never found the tape. It sat on my desk, hidden in plain sight. I succeeded by simply making it very difficult to complete the stack, not by being particularly creative.

Edgar Allan Poe wrote a famous story, 'The Purloined Letter', about such approaches. Place important information in the open, but surround it with tremendous amounts of extraneous, random information has been a favorite way of hiding it. The formal term is steganography and has a long history. My favorite is tattooing the message on the shaved head of a man, letting the hear grow back and sending him on his way with the message undetected!!

Now we all know about encryption, in which the message is altered into a different form and must be decoded before reading. Modern computing has made decoding encrypted messages easier. So using steganography offers some possibilities.

Here is one I am considering. Many programs scan messages looking for keywords. In the late '50s, Howard L. Chace created a novel language called the 'Anguish Language.' Here is a nice example. What he does is take homophones for the words we want to write. So, 'Little Red Riding Hood' becomes 'Ladle Rat Rotten Hut.' Makes no sense when written but it does when spoken.

So, you could write your message in 'Anguish'. Anyone using computers to scan for keywords will be very confused. You could form the message so that any computer looking at it will have real problems. Only people who read it aloud would decipher it. (As an added treat, check out this site that describes what happens when translation programs take 'Ladle Rat Rotten Hut' and translate it from English to German to French and back to English. It becomes 'Putrefied iron and steel plant of the rat of spoon'!! Pretty hard to figure that one out.)

Hiding codes in plain site using biological means has also been developed. A paper in Nature last year described it. A message was encoded using a simple substitution code (A=CGA, B=CCA, etc.). Each letter corresponded to a codon triplet. They made an oligonucleotide where each codon was one letter in the message. They also had PCR primers put on either end of the oligonucleotide. So, they could use the proper PCR primers to amplify this oligo, sequence it and read the message.

Now comes the spy part. They soaked some paper in the DNA solution. They then took a small microdot of the paper, glued it to a period in a sentence in the letter, mailed it to themselves. They isolated the oligo from the letter, amplified it up, sequenced it and read the message. What a great way to send messages. You can only read it if you know which period in a letter contains the right message. Adding lots of extraneous dots on the page would hamper finding the correct dot. You then have to have the proper primers. Without them you have nothing. You could go even further and use high-level encryption to create the message. Then, even if someone did find the right DNA sequence, they would have to further decode it.

A more recent use of steganography is taking place at the Summer Olympics in Sydney. A major way the organizing committee of a particular host city gets its money back is to sell the merchandising rights to the Games. SOCOG is really worried about fake Olympic merchandise. Counterfeit goods must be stopped since they will cut into the revenue. In the last Olympics, little holographic stickers were used. But merchants in the Far East have been able to easily duplicate these.

So, in these Olympics, they have a new idea. Along with a special fluorescent dye, they have added the DNA of an unknown Australian to a unique ink that is placed on all the merchandise. Again, they have the sequence surrounded by known primers but it is hidden in a huge background of random sequences. They will use this to verify any merchandise. Simply add the right primers and PCR it up. The large amount of extraneous DNA will make it very difficult to find the correct sequence. The expectation is that the merchants will not be able to counterfeit the DNA in this dye before the Olympics are over.

There is a company that has commercialized this technology. They used similar technology to verify Mark McGwire's home run balls. You can buy Joe Namath merchandise which has his DNA in it. Wow!! Wish I had thought of this idea. Make lots of money, meet famous people. All for hiding DNA in plain sight.