Add web platform support for Cashu key derivation via JS interop

[Copilot]

Web platforms require browser-native cryptography libraries for Cashu key derivation. The existing pure Dart implementation (DartCashuKeyDerivation) works on native platforms but needs JavaScript alternatives (@noble/hashes, @scure/bip32) on web.

Implementation

Conditional compilation via factory pattern:

• createCashuKeyDerivation() returns platform-specific implementation at compile time
• JsCashuKeyDerivation (web) - delegates to /web/js/cashu_key_derivation.js via dart:js_interop
• DartCashuKeyDerivation (native) - existing pure Dart implementation

JavaScript implementation:

• Ports TypeScript reference code to ES6 modules
• Loads @noble/hashes@1.3.3 and @scure/bip32@1.3.3 from esm.sh CDN (pinned versions)
• Supports v01 (HMAC-SHA256) and v00 (BIP32) derivation methods
• Input validation for hex strings, Base64, and keyset IDs

Integration:

// Before (init.dart)
cashuKeyDerivation: DartCashuKeyDerivation(),

// After
cashuKeyDerivation: createCashuKeyDerivation(),

Factory uses Dart's if (dart.library.js_interop) conditional imports to select implementation without runtime branching.

Notes

CDN dependencies introduce external runtime dependency. Consider bundling locally for production deployments requiring offline operation or strict SRI policies.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• another-nonexistent
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• dead-relay.example.com
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• dead.example.com
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• dev.mint.camelus.app
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• example.com
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• mint.example.com
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• mint.invalid
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• mock.mint
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• nonexistent-server
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• nos.lol
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• purplepag.es
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)
• relay.damus.io
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot (dns block)
  • Triggering command: /tmp/dart-sdk/bin/dartvm /tmp/dart-sdk/bin/dartvm --resolved_executable_name=/tmp/dart-sdk/bin/dart --executable_name=dart --mark_main_isolate_as_system_isolate .dart_tool/pub/bin/test/test.dart-3.10.8.snapshot 0 -j ACCEPT (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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