PROJECT DOSSIER // [DUO STUMPER 3]VIEW SOURCEBACK TO PROJECTS →

01 // PROJECT AT A GLANCE

DUO STUMPER 3

C

Encrypting and decrypting a file with Julius Caesar's two-thousand-year-old secret code.

The Caesar cipher shifts each letter by a fixed number of positions in the alphabet. Trivially simple in theory, but the program has to read an entire file, preserve anything that is not a letter, handle negative shifts and shifts larger than the alphabet, and work in both directions.

A command-line tool encrypting a file (-f) or a string (-s) by alphabetic shift, writing the result into a « crypt » file, with an alphabet table allocated at runtime for lower and upper case.

PRIMARYC
DELIVERY2-PERSON TEAM
VERIFICATIONCriterion
SOURCEINSPECTOR READY
MEDIA ATTACHMENTS (Images, Photos, Videos)

02 // PROJECT SIGNALS

DATE:
2018
PRIMARY LANG:
C
GRADE:
—
DURATION:
1 afternoon
SECONDARY:
—
STACK:
Makefile / gcc

03 // KEY OUTCOMES

  • Encryption preserving case and leaving everything non-alphabetic untouched
  • Shift brought back into [1;26]: negative and out-of-range values accepted, the direction resting on the sign alone

BEYOND THE BRIEF

  • A complete embedded library with my_printf and get_next_line, reused as is under time pressure
  • Criterion tests despite the timed format

04 // SOURCE TREE

READING SOURCE…