Caesar Cipher
Shift letters by any amount — encrypt and decrypt with a slider. Includes brute-force mode that shows all 25 possible decryptions at once.
Build Software with The Spy's Knife
Ciphers, codes, and covert tools — all offline
You need to build software. Developer utilities — offline, forever. The Spy's Knife delivers 11 purpose-built tools in a single HTML file.
The Spy's Knife is a cryptographic playground in a single HTML file. Encrypt and decrypt with over ten classical ciphers, hide messages in images with steganography, generate number station broadcasts, create QR codes and barcodes, and simulate invisible ink with UV-effect CSS — all running locally with zero network calls.
WHAT'S INSIDE
11 tools in a single HTML file
Vigenère Cipher
Encrypt with a keyword-based polyalphabetic cipher. Shows the Vigenère table and highlights the path through it for each character.
Atbash Cipher
A simple substitution cipher that reverses the alphabet — A↔Z, B↔Y. One click to encode, one click to decode.
ROT13
The classic rotate-by-13 cipher — applying it twice gives you back the original. Useful for hiding spoilers and puzzle answers.
HOW IT WORKS
Three steps. No setup.
1
Download the file
Purchase The Spy's Knife and download a single HTML file. No installer, no account, no setup.
2
Open in any browser
Double-click to open in Chrome, Firefox, Safari, or Edge. Works on any operating system.
3
Start working
Your data stays in your browser's local storage. Nothing is uploaded. Ever.
COMPLIANCE & GEOGRAPHY
Global
Works in any country. No server dependency, no regional restrictions.
FAQ
Frequently Asked Questions
How does The Spy's Knife help me build software?
The Spy's Knife provides 11 interconnected tools for developer utilities — offline, forever. Ten+ cipher algorithms, steganography, number station generator, QR encoder, barcode generator, and invisible ink simulator. For puzzle makers and escape room designers.
Do I need an internet connection to build software with The Spy's Knife?
No. The Spy's Knife runs entirely in your browser as a single HTML file. All 11 tools work offline.
What is the difference between The Spy's Knife and cloud-based alternatives?
Cloud tools store your data on external servers, require subscriptions, and stop working without internet. The Spy's Knife is a one-time purchase ($39) that runs locally. Your data never leaves your device.
Can I use The Spy's Knife on multiple devices?
Yes. Once purchased, you can use The Spy's Knife on any device with a web browser. Copy the HTML file to as many devices as you need.
No cloud One fileOne-time purchase
Get The Spy's Knife — $39Sovereignty as a Service