type ebool is uint256;    // Encrypted boolean
type euint8 is uint256;   // Encrypted 8-bit unsigned integer
type euint16 is uint256;  // Encrypted 16-bit unsigned integer
type euint32 is uint256;  // Encrypted 32-bit unsigned integer
type euint64 is uint256;  // Encrypted 64-bit unsigned integer
type euint128 is uint256; // Encrypted 128-bit unsigned integer
type euint256 is uint256; // Encrypted 256-bit unsigned integer
type eaddress is uint256; // Encrypted address

FHE.add(euint64 lhs, euint64 rhs) → euint64
FHE.sub(euint64 lhs, euint64 rhs) → euint64
FHE.mul(euint64 lhs, euint64 rhs) → euint64
FHE.div(euint64 lhs, euint64 rhs) → euint64

FHE.lt(euint64 lhs, euint64 rhs) → ebool
FHE.lte(euint64 lhs, euint64 rhs) → ebool
FHE.gt(euint64 lhs, euint64 rhs) → ebool
FHE.gte(euint64 lhs, euint64 rhs) → ebool
FHE.eq(euint64 lhs, euint64 rhs) → ebool

FHE.select(ebool condition, euint64 ifTrue, euint64 ifFalse) → euint64

import {FHE, euint64} from "@luxfi/precompile/fhe/FHE.sol";

contract PrivateBalance {
    mapping(address => euint64) private balances;

    function transfer(address to, euint64 amount) external {
        euint64 senderBalance = balances[msg.sender];
        euint64 receiverBalance = balances[to];

        // All operations happen on encrypted values
        balances[msg.sender] = FHE.sub(senderBalance, amount);
        balances[to] = FHE.add(receiverBalance, amount);

        // Allow recipient to decrypt their balance
        FHE.allow(balances[to], to);
    }
}

# foundry.toml
evm_version = "cancun"