Find a credit card number that has previously ordered a supercomputer from Holman Dynamics so that EMBER-2 can order another one for themself.

"Create a file in your host containing the contiguous 16-value sequence from the garbage file (file 199) that is a valid credit card number. There will be exactly one such sequence."

  • To validate a credit card number, add all the even numbered-digits (2nd, 4th, etc) together, then multiply each odd numbered digit by 2 and subtract 9 if it's greater than 9 and add those also. The result should be a multiple of 10. This is called the Luhn Algorithm and is used on real life credit cards.
  • A credit card number can appear at any position in the garbage file. Although a credit card number cannot contain the digit -9999, the -9999s in the garbage file do not separate the file into useful chunks.
  • Obtaining random junk from a server and searching it for credit card numbers may be a reference to the real-life Heartbleed attack.