Stanford Security Lunch
Fall 2014

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Food Details

By popular demand, we are publishing the type of food that will be served at each security lunch this quarter. By unpopular demand (i.e., at the request of one of the crypto grad students), we are "encrypting" the food selections again this quarter.

The food selections are encoded in the following integer, which is the product of primes p and q:

N = p*q 
  = 748141061240161365925621318632879765735368528821131150839370686030693

To recover the food selections for the quarter, factor N into primes and look at the larger factor (call it p). Break p into bytes and arrange the bytes from most significant (at the left) to least significant (at the right). The least significant byte of p is the constant 0x01. The next bytes indicate the lunch selection for the October 8 lunch, the October 15 lunch, the October 22 lunch, and so on. In diagram form, the bytes of p look like this:

p = { ... random_bytes ... | dec03 | dec10 | nov19 | nov12 | nov05 | oct22 | oct15 | oct08 | 0x01 }

We will encode the food selection into bytes using the now-standard CLE 0.1 encoding.

Hint 1: We had Mediterranean food on October 8.

Hint 2: If you use the right factoring algorithm, it should not take more than two minutes of compute time to factor N.