My Passphrase

A passphrase and password generator in one self-contained HTML file. No build, no dependencies, nothing ever sent over the internet: download one file, open it in a browser, done. It works with the Wi-Fi off, and a Content-Security-Policy tells the browser to refuse if anything on the page ever tried to phone home.

Truly random. Centuries to crack. Humans are terrible at inventing passwords. A passphrase, a handful of words chosen truly at random, is easier to remember than Tr0ub4dor&3 and far harder to guess.

Features

• Five generation pools
  • The EFF large wordlist: 7,776 words curated by the Electronic Frontier Foundation for passphrases, the same list diceware uses
  • Common English: 7,459 everyday words from a frequency corpus, for phrases that read a little more naturally
  • ASCII characters: all 94 printable ASCII symbols, for a classic ipz2!az8k%0h-style password where a manager autofills or a length limit bites
  • Hex digits: 16 to 64 random hex digits, four bits each, for wallet entropy and anything else that wants its randomness machine-shaped; 64 digits are exactly 256 bits, counted rather than estimated
  • PIN digits: 4 to 12 random digits for the PINs hardware wallets ask you to set; drawn per digit, so leading zeros are as likely as anything else (0042 is a valid PIN, which range-style generators cannot produce)
• Real randomness: every draw comes from crypto.getRandomValues with rejection sampling, so each word and character is exactly as likely as every other; Math.random appears nowhere in the file
• Entropy first: the meter measures randomness in bits and says so in the headline, because that is a property of the secret itself. Crack time is a consequence of it and rides underneath. The bar runs 0 to 128 bits, linear, with a 💪 mark at 78 bits, which is six words and the point past which offline guessing stops being a threat, and 🌱 at 128, as much randomness as the 12-word seed phrase behind a bitcoin wallet. Everything right of 💪 is green: 128 is a comparison, not a bar to clear
• Honest accounting: generated secrets show their true entropy (words × bits per word), never an estimate. Typed text is zxcvbn's estimate and is labelled est., held under two ceilings the page can prove: a word on one of the lists cannot be worth more than the list it came from, since anyone who knows the recipe simply tries all 7,776, and text written entirely in a small alphabet, such as 32 hex digits, cannot be worth more than that alphabet carries per character. Both only ever lower a figure and credit none. Edit the box to test any password of your own
• Make it stronger (💪): one press capitalises a random letter anywhere in a generated phrase and adds a random digit or symbol at a word's edge, taking turns, so two presses cover the capital, digit and symbol that many sites ask for. The same RNG makes every choice, so the gain is counted, not estimated, and priced as if an attacker knows the button exists; the button shows what the next press is worth. Symbols that appear in the word lists, or that sites often refuse (quotes, backtick, backslash, angle brackets), are never used
• Encode and decode: a separate card spells the exact secret in another alphabet for the sites and devices that demand one: hex, Base64, Base32, Base58, binary, octal, or decimal bytes, with its own reveal, copy and QR controls. Its Encode field follows the passphrase box until you type your own text into it. Below it, Decode takes a pasted string and reads back the text it holds; if the alphabet you picked is wrong, it names the ones the string does read in, and one press sends the decoded text to the meter. A conversion adds zero bits and decoding needs no key, because anyone who knows the alphabet reads it straight back, so a string deserves the same care as the phrase itself
• One headline attack speed, three in the detail: the crack time assumes a trillion guesses a second, the pessimistic end, since you never get to choose how well a site guards what you gave it. Details costs the same secret at three speeds, because they span nine orders of magnitude and which one you face is a property of what holds the secret rather than of the secret: a login that throttles at 1,000 a second, a stolen wallet backup at 10 million (BIP-39 puts every guess through 2,048 rounds of work), and a stolen password file at a trillion
• Blurred by default: a generated secret arrives as smudges, with in-field eye, copy, and QR controls; the eye is a sticky per-session preference
• QR export: show the secret as a plain-text QR (blurred until revealed) for wallets that scan a passphrase in, such as Krux, instead of making you type it on-device
• No secret before you ask: nothing is generated on page load
• A sentence gets a warning: the estimator prices words one at a time and cannot see that grammar makes the next one easy to guess, so a sentence scores like a passphrase while being nothing of the kind. Sentence-shaped text says so plainly rather than being quietly flattered
• Light and dark themes: light is the default for everyone, deliberately, rather than following the OS. The choice you make is remembered

Use it

Step 1: Download the file, while still online

Download mypassphrase.html from the latest release. Every release publishes the SHA-256 of the file alongside it. Check the one you downloaded against it before you open it:

# macOS
shasum -a 256 ~/Downloads/mypassphrase.html

# Linux
sha256sum ~/Downloads/mypassphrase.html

# Windows (PowerShell)
Get-FileHash $HOME\Downloads\mypassphrase.html -Algorithm SHA256

If what you get is not the value published on the release page, stop. Do not open the file.

That tells you the file is the one published. It cannot tell you the published one is honest; reading it is what checks that, and it is written to be read.

Cloning the repo works too: index.html there is the same file, named for the web server that has to serve it at the domain root.

Step 2: Go offline for anything that matters

For a passphrase that will guard something important: go offline first. Turn off Wi-Fi, open the downloaded file in a browser profile with no extensions, generate, and store the result in a password manager (or memory) before reconnecting. The page's badge shows whether you are offline.

There is no build step. The file you download is the source, readable in any text editor: the wordlists, the RNG, the strength meter, and the two embedded libraries are all in plain sight.

Security

The page never touches the internet (no images, no fonts, no scripts) and its CSP (default-src 'none') makes the browser enforce that. Nothing typed or generated is stored, logged, or sent. What a web page cannot defend against (browser extensions, a compromised machine, clipboard snooping) is documented in the page's own Q&A and in SECURITY.md, which also explains how to report a vulnerability.

Credits

• Generator and crack-time code adapted from mike-hearn/useapassphrase (ISC)
• Strength estimation by zxcvbn, created at Dropbox by Dan Wheeler (MIT), embedded verbatim
• QR encoding by qrcode-generator (Kazuhiko Arase, MIT), embedded verbatim
• EFF large wordlist (CC-BY 3.0)
• Common-English list derived from first20hours/google-10000-english
• Design adapted from the sister project, seQRets/My-Seed-Phrase

License

MIT © Toothjockey LLC