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Save encrypted data in HTML file as Base64 #229

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Save encrypted data in HTML file as Base64 #229

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@jimhark jimhark commented Jul 21, 2025

Summary

Store encrypted data, which is as large as the source html file, as Base64. Reduces size by 1/3 and improves performance.

Store the encrypted data as Base64. A data URL is a great way to store data in an HTML file, and it supports Base64 encoding.

Fixes

Fixes #228

Details

  • password_template.html: div added to hold data URL
  • cryptoEngine.js provides Base64Encoder
  • cli/index.js: encryptedMatch now matches the data URL, and is parsed using Base64Encoder
  • staticryptJs.js: getEncrypted() reads encrypted data from DOM and returns Uint8Array

Testing

I manually tested node encrypt, node decrypt, and HTML wrapper decrypt.

Notes for Reviewers

Pay attention to how fast a large web page is encrypted and decrypted. Also note file size.
jimhark and others added 7 commits July 20, 2025 20:51
@jimhark
On Node, HexEncoder.stringify now uses Buffer.toString('hex')
0851c28
Refactor: prefer Uint8Array as internal representation of binary data
0a096f6 
This is part of a push to support larger files. The focus is the switch
to using Uint8Array to store binary data. But also includes:

- When running on Node, use Buffer.from() for hex string conversions.

- To avoid large buffer copy, signedMsg as been replaced by an object
    containing  iv, encrypted, and hmac.

- hmac calculation has changed so it avoids copying (possibly very
    large) encrypted data. See signDigest() in lib/codec.js.

- Minor cleanup

Handling hex encode/decode at the input/output boundaries and using
Uint8Array internally for representing binary data has these benefits:

- More memory efficient, allows processing of 2x larger files.

- Aligns with cryptographic best practices: hashing is now performed
  on raw binary data (Uint8Array) instead of hex strings.

- Behavior is (mostly) unchanged
  - scripts/index_template.html textContent is not implemented and
    needs to be redesigned.
Update browser version of HexEncoder parse()
f2388b5
Minor cleanup of getRandomAlphanum()
fd3adc9
renderTemplate() - added named return var
0a71e4f 
makes unnamed function more self documenting
Rewrote decode() to avoid multiple hashing of encrypted.
08a8e7a 
Also removed use of recursion to improve readability (and debugability).
As a bonus, function is actually shorter (LoC AND lines of text)
write encrypted data as Base64 (not hex string)
9feacd8 
cuts size by 1/3 and noticeably improves performance
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