bytes32 key = ... ;
bytes32 nonce = ... ;
bytes memory text = "plain text";
bytes memory ad = "additional data";
bytes memory encrypted = Sapphire.encrypt(key, nonce, text, ad);
bytes memory decrypted = Sapphire.decrypt(key, nonce, encrypted, ad);

bytes memory seed = hex"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef";
bytes memory publicKey;
bytes memory privateKey;
(publicKey, privateKey) = Sapphire.generateSigningKeyPair(Sapphire.SigningAlg.Ed25519Pure, seed);

function signTransaction(uint64 nonce, uint256 gasPrice)
    internal returns (bytes memory)
{
    (address signerAddr, bytes32 signerSecret) = EthereumUtils.generateKeypair();

    payable(signerAddr).transfer(1 ether);

    return EIP155Signer.sign(
     signerAddr, signerSecret,
     EIP155Signer.EthTx({
            nonce: nonce,
            gasPrice: gasPrice,
            gasLimit: 250000,
            to: address(this),
            value: 0,
            data: data,
            chainId: block.chainid
        }));
}

import {Host, Result} from "@oasisprotocol/sapphire-contracts/contracts/OPL.sol";

contract Sender is Host {
 event HeardReply(string);  

constructor(address _receiver) Host(_receiver) {
   registerEndpoint("listenToReply", _listenToReply);
 }  function sendToListener(string memory _message) external payable {
   postMessage("confirmMessage", abi.encode(_message));
 }  function _listenToReply(bytes calldata _args) internal returns (Result) {
   (string memory reply) = abi.decode(_args, (string));
   emit HeardReply(reply);
   return Result.Success;
  }
}