JavaScrypt, available at Fourmilab since 2005, is a symmetrical, military-grade (Advanced Encryption Standard, 256 bit key) cryptographic system which runs entirely within any Web browser that supports the basic JavaScript language. If you have downloaded JavaScrypt to a file on the computer, you can run it without a connection to the Internet and on an “air-gapped” machine with no external connections at all. Utilities are included for key generation, encoding encrypted messages in a variety of forms for transmission, and steganography (hiding encrypted messages in text).
The master source code archive and development environment for JavaScrypt is now available on GitHub. This provides transparency for changes made to the code, provides a starting point for those who wish to modify or extend the package, and allows submitting fixes or requests for change to the package. The version of JavaScrypt available from Fourmilab remains unchanged: this simply provides a simpler and more flexible way to obtain and manage the source code and development environment used to build it.