func AgentSeal(msg, clientPub []byte, agentKey *ecdsa.PrivateKey) ([]byte, error) {
	pubKey, err := ethcrypto.UnmarshalPubkey(clientPub)
	if err != nil {
		return nil, err
	}

	pub := ecies.ImportECDSAPublic(pubKey)
	msgEncrypted, err := ecies.Encrypt(rand.Reader, pub, msg, nil, nil)
	if err != nil {
		return nil, err
	}

	return PackWithSignature(msgEncrypted, agentKey)
}
func AgentSeal(msg, clientPub []byte, agentKey *ecdsa.PrivateKey) ([]byte, error) {
	pubKey, err := ethcrypto.UnmarshalPubkey(clientPub)
	if err != nil {
		return nil, err
	}

	pub := ecies.ImportECDSAPublic(pubKey)
	msgEncrypted, err := ecies.Encrypt(rand.Reader, pub, msg, nil, nil)
	if err != nil {
		return nil, err
	}

	return PackWithSignature(msgEncrypted, agentKey)
}
// AgentSeal encrypts message using client's public key and packs with
// agent signature.