Summary of subtle.importKey/exportKey Implementation

Core Functionality Added:

1. EC (ECDSA/ECDH) SPKI/PKCS8 Support

   • Implemented ecExportKey() for SPKI and PKCS8 formats
   • Added EC key import/export for P-256, P-384, P-521 curves
   • Both public (SPKI) and private (PKCS8) key formats now supported

2. HMAC Export Support

   • Implemented JWK and raw format export for HMAC keys
   • Added base64url encoding with period padding for JWK compatibility

3. Base64url Period Padding

   • Fixed JWK import/export to handle non-standard period padding (used by some JWK implementations)
   • Added period stripping on import and period addition on export for roundtrip compatibility

4. Error Message Fixes

   • Standardized error messages across implementations
   • Fixed validation order for HMAC zero-length keys

Test Coverage:

• Added 26 new tests covering EC, RSA-OAEP, RSASSA-PKCS1-v1_5, and secret key formats
• All tests in the subtle.importKey/exportKey suite now pass