input.md

Input registration

This document explains how to register ciphertexts to the FHEVM. Registering ciphertexts to the FHEVM allows for future use onchain using the FHE.fromExternal solidity function. All values encrypted for use with the FHEVM are encrypted under a public key of the protocol.

// We first create a buffer for values to encrypt and register to the fhevm
const buffer = instance.createEncryptedInput(
  // The address of the contract allowed to interact with the "fresh" ciphertexts
  contractAddress,
  // The address of the entity allowed to import ciphertexts to the contract at `contractAddress`
  userAddress,
);

// We add the values with associated data-type method
buffer.add64(BigInt(23393893233));
buffer.add64(BigInt(1));
// buffer.addBool(false);
// buffer.add8(BigInt(43));
// buffer.add16(BigInt(87));
// buffer.add32(BigInt(2339389323));
// buffer.add128(BigInt(233938932390));
// buffer.addAddress('0xa5e1defb98EFe38EBb2D958CEe052410247F4c80');
// buffer.add256(BigInt('2339389323922393930'));

// This will encrypt the values, generate a proof of knowledge for it, and then upload the ciphertexts using the relayer.
// This action will return the list of ciphertext handles.
const ciphertexts = await buffer.encrypt();

With a contract MyContract that implements the following it is possible to add two "fresh" ciphertexts.

contract MyContract {
  ...

  function add(
    externalEuint64 a,
    externalEuint64 b,
    bytes calldata proof
  ) public virtual returns (euint64) {
    return FHE.add(FHE.fromExternal(a, proof), FHE.fromExternal(b, proof))
  }
}

With my_contract the contract in question using ethers it is possible to call the add function as following.

my_contract.add(
  ciphertexts.handles[0],
  ciphertexts.handles[1],
  ciphertexts.inputProof,
);