# CAMP 2020 Day 5 – again next summer

Today is our last day at CAMP 2020. We felt heartbroken to say goodbye to all the CAMPers. It was wonderful having you with us this week: the time we spent together was truly a highlight of our summer, notwithstanding we were all staying home.

• Math with Japheth, Erin, and Frances: At 1 PM in Japheth’s class, the COT group approached the second to last class for the entire program. After their discussion on the Hill cipher and two by two matrices modulo 26 on Wednesday and Thursday, the group focused on analyzing invertible ciphers and matrix ciphers.

If y = f(x) = y and we have g (f(x)) = g (y) = x, we call g (y) the inverse function of f (x). Not all ciphers were created equal, some like the MULT-2 (Multiplication cipher times 2) does not have an inverse function corresponding to it. CAMPers discussed the possible invertible ciphers from the various kinds they had become familiar with over the week. Later we went into the breakout room for more mathematical problems and group discussions.

CAMPers were also curious about what websites or apps Japheth uses to type math equations and symbols efficiently. Our instructor shared a few options (Overleaf!) he knows to encourage students to explore math further after CAMP ended.

Our senior math instructor Erin, teaching the COS and SIN sections, rediscovered a code that she shared with a 7th grade class years ago. Her class decrypted the first few parts of a text created with the intention to be easily decoded… by aliens! It’s an Active SETI (Active Search for Extraterrestrial Intelligence) message that was sent as an interstellar radio message in 2003 (directed toward nearby star systems). Scientists were hoping that extra-terrestrials could potentially decode the message and learn a bit about earth—what a fun background behind the history of this code.

• Brute-Force algorithm in programming: At the last classroom period with CAMP 2020, CS instructor Karen helped students perfect an encoding/decoding game. For the last few days, CAMPers studied various functions in the Python language, coding a program to encrypt and decrypt messages quickly with the given keys.

Today, we studied the Brute-Force algorithm — one way to decode the message without the key. Although this method has a clear bias for English speakers with spelling ability (we still need to hand-select the original plaintext from 26 choices of keys), the Brute-Force algorithm is commonly used for examining the security-level of crypto-systems

After watching Karen’s demo on screen, students all coded their own cipher game ready to be tested. CAMPer Advika offers the group to run a secret message she made yesterday. Among all the possible plain texts, we noticed that “hovercam” seems to be the correct answer.

• Knot cipher: Last day in the art classroom, we designed a knot cipher with art instructor Tiffany and Chelsea.

• During the activity period, our team sent out a survey for their experience at CAMP before students played games with their TAs. We inquired about whether they were comfortable with the level of material, the pacing of the class, and what they liked best about CAMP to help us improve in the next summer.

It was a lovely but short journey with CAMPers and families this year. Hope to see you again next summer.