Silent Partner
A free, private back-office helper for small businesses. It keeps track of money all year so
decisions like "how much can we give or spend?" take minutes instead of a week.
Built for ENT 1000 (Washington and Lee, Fall 2026) by Jillian Gangaram, with Caitlyn Crouch and
Claudia Ramirez. It's based on our interviews with local businesses, especially the Scot Shop.
What it does
- Safe-to-spend number: money left after upcoming bills and a cushion for surprises, with every line of the math shown
- Can we afford it?: checks a specific amount and pushes back, naming the bills at risk, if it's too risky
- Sports Club check: the end-of-year distribution. Holds back what the shop needs to open next
season and the management checks, then shows what's left for the Sports Club, with the work shown
- Management checks: splits the management pool between the people who get a check, evenly or by
weighted shares
- Expense log: missing details, possible duplicates, and big amounts get flagged for the owner to confirm
- Bills & sales: bank balance, weekly sales (POS spreadsheet import), and repeat bills
- Weekly update: a plain-language text summary to copy. Nothing is ever sent automatically
- Pricing: shows whether a product still makes money once the owner pays themselves
- Keeping the books: optionally saves every change to a private GitHub repository, so the
books survive the computer and follow you to another device. Off until you set it up; see
SETUP-SYNC.md
- A walkthrough for the owner:
guide.html, 27 pages in plain English with a picture of
every part of the site. Linked from the lock screen and the top bar
The owner makes every decision. The site organizes, flags, and recommends.
Privacy
- One shared password opens blank Scot Shop books. They ship encrypted in
blank-vault.js
(AES-256-GCM, key stretched with PBKDF2-SHA256, 310k rounds). There are no numbers in them at
all: just the store manager's own set-up, so she can start typing instead of configuring.
The sample-number demo that used to ship alongside has been deleted, so there is no way for
the site to show a figure that nobody typed in. Books from a browser that had loaded the demo
are emptied automatically the first time they're opened.
- Anything a visitor types afterwards is encrypted with that same password and stored only in
their own browser. Nothing is uploaded, and no visitor can see another visitor's numbers.
That stays true unless the owner deliberately turns on saving to GitHub, below.
- The site locks itself after 15 minutes without use.
- The page is marked
noindex and robots.txt blocks crawlers, so it stays link-only.
What the password does and does not do. It is a door, not a vault. The shared password is a
single short word that several people know, and blank-vault.js is served to anyone who loads the
page — so someone determined, with that file in hand, can guess at the password offline. That
matters very little while the file is empty, which is exactly why what ships is empty.
It starts to matter the moment real figures are typed in. Those figures are encrypted and stay in
that one browser, so guessing the shared password off the website does not reveal them — an
attacker would also need the machine. But anyone who knows the shared word and can reach the
computer can open the books.
So: whoever enters real numbers should change the password first. Settings → Privacy &
password, one long phrase nobody else has. Until that happens the site says so in a banner on
every page. After that, the shared word no longer opens those books, and a backup downloaded
beforehand still needs the old one.
Keeping the books: saving to GitHub
Everything above lives in one browser on one machine, which is private but fragile: clear the
browser, switch to the shop iPad, or hand the shop over to the next manager, and it's gone.
Settings → Keeping your books turns on saving to a private GitHub repository. After every
change the same sealed file is written there through the GitHub API, using a fine-grained token
with write access to that one repository and nothing else. Every save is a commit, so the
repository doubles as an undo history nobody has to maintain. Full instructions, including how to
confirm it actually worked: SETUP-SYNC.md.
What the repository can see: the ciphertext, the salt, the iv, and the time each save was made
and from which device. Not the password, which never leaves the browser, and not one number.
Two people can work at once. The books are merged row by row rather than file over file, so
nobody's entries get wiped by whoever saved second: both sides' rows are kept, the later edit
wins a genuine clash, and a deleted row stays deleted instead of coming back from the other
device.
Three suites cover this, 65 cases in total, all exiting 0 when they pass:
node tools/sync-selftest.mjs # the merge rules on their own
node tools/sync-roundtrip.mjs # two devices against a stand-in for the GitHub API
node tools/browser-check.mjs # the real page in headless Chrome: unlock, type, reload, delete
Two things to know before turning it on.
The site refuses to sync books that still use the shared password, on purpose. A short word
several people know is a fine door while the books sit in one browser. Once the sealed file is on
a server, it can be guessed at offline by anyone who gets a copy. Set your own password first.
The token is kept in the browser, because the page has to reach the repository before anyone has
unlocked anything. Whoever can use that computer can therefore write to that one private
repository, though they still can't read a number without the password. On a shared machine,
press Stop saving to GitHub when you're done.
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