Let's recall our current stack:

• ferveo: Core cryptographic implementation (Rust -> WASM)
• nucypher-core: Protocol API and objects (Rust -> WASM)
• taco-web: Adopter-facing API (TypeScript)

The scope of this issue is to investigate to what extent we can build a minimal substitution for ferveo and nucypher-core using purely TypeScript primitives. Since browser interactions are currently tied to the creator/encryption and consumer/decryption request steps, let’s investigate what happens underneath and what do we need to replace.

Encryption (taco/src/tdec.ts/encryptMessage()):

• nucypher_core::encryptForDkg(data: Uint8Array, public_key: DkgPublicKey, conditions: Conditions)
  • ferveo_tdec::api::encrypt(message, aad, public_key, rng):
    • BLS12-381 arithmetic
    • ChaCha20Poly1305 encryption
    • Rust-side serialization
• nucypher_core::AccessControlPolicy
• nucypher_core::ThresholdMessageKit

Decryption (taco/src/tdec.ts/retrieveAndDecrypt()):

• nucypher_core::
  • ThresholdDecryptionRequest
    • .encrypt()
      • EncryptedThresholdDecryptionRequest
        • encrypt_with_shared_secret
          • ChaCha20Poly1305 encryption
  • SessionStaticSecret
    • .new()
      • crate::secret_box::kdf (HKDF)
    • .derive_shared_secret()
      • x25519_dalek::{PublicKey, SharedSecret, StaticSecret}
  • EncryptedThresholdDecryptionRequest
    • encrypt_with_shared_secret
    • decrypt_with_shared_secret
  • ThresholdMessageKit
    • .decryptWithSharedSecret()
      • ferveo::api::decrypt_with_shared_secret
        • SecretBox
        • Chacha20Poly1305
• ferveo::binding_wasm::combine_decryption_shares_simple
  • ferveo::api::combine_shares_simple
    • BLS12-381 arithmetic

After this preliminary analysis, we can see that we currently depend on these external primitives:

• BLS12-381 arithmetic
• ChaCha20Poly1305 encryption
• HKDF
• x25519_dalek
• SecretBox
• Rust-side serialization

A cursory search I can see several 3rd party libraries that can help us with this process, but we need a more in-depth investigation.

• BLS12-381 and x25519 pure TS/JS implementation:
  https://github.com/paulmillr/noble-curves/blob/94d00668f19ea38a6956cc0afe1051038b764fcb/README.md?plain=1#L46
• ChaCha20Poly1305 implementation:
  https://github.com/paulmillr/noble-ciphers
• HKDF: https://github.com/panva/hkdf