Cryptography Event Description

Our event is designed so that students can walk in with no preparation and spend a busy -- and hopefully enjoyable -- 45 minutes solving progressively harder codes. To reward the prepared student, there will also be questions about specific types of code. To compete for the highest possible score, students should have a working knowledge of the following terms:

1) Simple ciphers, as found on: http://www.nsa.gov/kids.

2) Vigen`ere Cipher

3) Ascii & binary (students do not have to memorize the characters)

4) Modulus (e.g., 28 mod 11 = 6)

5) RSA Encryption

Four sample questions:

1) Decode the following welcome message which is encoded by the Rail Fence cipher:

"hlotsdns elsuetx"

2) What is the most widely used strategy to crack a simple substitution code?

3) Why are prime numbers used in some types of cryptography?

4) You have forgotten your 4 digit atm card password number. Fortunately, your best friend, who is into cryptography, knows your password number. However, you suspect that someone has been hacking into your emails, so you send the following email to your friend: "Please send me my password number in code using RSA encryption and this public key: N = 16781 and e = 5." You do NOT tell your friend that N = pq, where p = 97 and q = 173. (Note that 97 and 173 are both prime numbers.) Your friend replies with the following email: "Using the public key you sent me, I have encoded your 4 digit atm password number as 5347." Even if your hacking enemy reads BOTH of those emails, (s)he would have to be lucky to break the code. What is your four digit atm password number?

What to bring in:

1) Notes -- handwritten and/or printout.

2) Calculators may be useful.

Students are not allowed to bring in books of any kind or laptop computers.

Suggestion: a team would benefit by having four members so they could split up the questions.

Questions? Contact michael_krieger@wellesley.mec.edu or larry_lovett@wellesley.mec.edu.