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🔀 Fhenix Differences For Developers

You might be familiar with fhevm, which is a fork of the Ethereum Virtual Machine that supports homomorphic encryption by Zama.

While Fhenix uses a similar FHE cryptography, it does not use fhevm. However, in order to make the FHE ecosystem as accessible as possible, we have chosen to maintain compatibility in most interfaces, except when we felt that the developer experience was significantly improved by making changes.

In this page, we try and document the differences that developers should be aware of.

Differences​

  • fhenix.js is the recommended Javascript library for interacting with Fhenix smart contracts.
  • FHE library is available at the npm repository @fhenixprotocol/contracts.
  • cmux is named select.
  • reencrypt is named sealoutput or seal.
  • Operations can be called directly as properties of encrypted types (e.g. euint32.add(euint32) instead of FHE.add(euint32, euint32)).
  • Operations between encrypted types expect the types to match (e.g. euint32 + euint32 instead of euint32 + euint64)).
  • In Fhenix, we recommend using the inEuintXX input types instead of raw bytes when receiving encrypted data.
  • Conversion to other encrypted types can be done using the .toUxx functions. E.g. euint32 b = a.toU32();
  • Division by zero will return a MAX_UINT value instead of throwing an error (e.g. euint8(1) / euint8(0) will return euint8(255) instead of throwing an error).
  • Permits and Permissioned contracts are the recommended way to handle access to sensitive data in Fhenix. To read more about permits and access control, see Access Control.
  • Sealing and Decryption can be accessed using .seal and .decrypt respectively.
  • Large bit sizes are supported (including eaddress), with a limited instruction set