DECpedia: an offline encyclopedia for Data Encryption and Codes

DECpedia is an offline Mac app for studying Data Encryption and Codes. It brings together 121 entries in Italian and English, with worked examples, formulas, proofs and interactive logic games.

Alessio wanted a way to find a concept and follow its connections without constantly switching between PDFs. He provided the idea and selected the sources; OpenAI GPT-6 developed the app and additional learning material through Codex.

See how the topics fit together

RSA builds on modular arithmetic. Coding theory draws on linear algebra and polynomials. DECpedia links those ideas: each entry points to the background you need and the topics that follow, so you can revisit a prerequisite when a step doesn’t make sense.

The sidebar groups entries by subject, and search covers titles and explanations in both languages. From one page, you can read a definition, work through an example and follow a link to a related concept.

Go back to the source

References point to pages in the four course PDFs, notes prepared from lectures and supporting mathematics texts. The app’s explanations and worked solutions are clearly distinguished from the original documents.

The public download does not include these PDFs. When you open a reference, the app asks you to select a local copy you have permission to use. Page references help you check the source without searching through the whole document.

Work through the reasoning

Explanations start with an example or an intuitive idea before introducing definitions, notation and calculations. Worked exercises show intermediate steps, including power tables, linear systems and checks on the final answer. You can also copy a formula’s LaTeX source.

Advanced topics include their own background material. The Riemann–Roch entry has twenty prerequisite chapters, covering algebra, divisors, differentials and more. The prime number theorem entry has eight, including the zeta function and Newman’s lemma. Supporting definitions and proofs sit within the entry, and the full material is available in both languages.

Learn by making a move

Eleven logic games offer thirty-three levels. You can coordinate modular gears, reconstruct messages encrypted with a reused key, fix parity errors or plan jumps between points on a curve. Proof-based games ask you to collect the lemmas needed to complete an argument.

Each move changes the board. Finishing a level reveals an explanation that connects your choices to the mathematics, with links to topics worth reviewing. Undo, Restart and Hints are always available. There are no timers or online leaderboards.

Version 1.5.0 adds twenty-four illustrations for game objects, including levers, lamps, keys, bridges and a courier. Their appearance reflects the board’s state, while formulas and explanations remain easy to read. The games are original additions to the app, separate from the exercises in the PDFs.

Keep your study materials on your Mac

Choose a light or dark theme, or let the app follow macOS. Your bookmarks, notes, history and preferences are saved locally. Completed game results are saved too; unfinished boards remain available while the app session is open.

Entries, formulas and the resources needed to read them are bundled with the app for offline use. No account or online service is required. Source PDFs stay separate and open from your own local copies.