let virgil = VSSVirgilApi(token: "[YOUR_ACCESS_TOKEN_HERE]")

// initialize Virgil crypto instance
// enter User's credentials to create OTC and LTC Cards
let secureChatPreferences = SecureChatPreferences (
    crypto: "[CRYPTO]", // (e.g. VSSCrypto())
    identityPrivateKey: bobKey.privateKey,
    identityCard: bobCard.card!,
    accessToken: "[YOUR_ACCESS_TOKEN_HERE]")

// this class performs all PFS-technology logic: creates LTC and OTL Cards, publishes them, etc.
self.secureChat = SecureChat(preferences: secureChatPreferences)

try self.secureChat.initialize()

// the method is periodically called to:
// - check availability of user's OTC Cards on the service
// - add new Cards till their quantity reaches the number (100) noted in current method
self.secureChat.rotateKeys(desiredNumberOfCards: 100) { error in
    //...
}

func sendMessage(forReceiver receiver: User, message: String) {
    guard let session = self.chat.activeSession(
        withParticipantWithCardId: receiver.card.identifier) else {
        // start new session with recipient if session wasn't initialized yet
        self.chat.startNewSession(
            withRecipientWithCard: receiver.card) { session, error in

            guard error == nil, let session = session else {
                // Error handling
                return
            }

            // get an active session by recipient's Card ID
            self.sendMessage(forReceiver: receiver,
                usingSession: session, message: message)
        }
        return
    }

    self.sendMessage(forReceiver: receiver,
        usingSession: session, message: message)
}

func sendMessage(forReceiver receiver: User,
    usingSession session: SecureSession, message: String) {
    let ciphertext: String
    do {
        // encrypt the message using previously initialized session
        ciphertext = try session.encrypt(message)
    }
    catch {
        // Error handling
        return
    }

    // send a cipher message to recipient using your messaging service
    self.messenger.sendMessage(
        forReceiverWithName: receiver.name, text: ciphertext)
}

func messageReceived(fromSenderWithName senderName: String, message: String) {
    guard let sender = self.users.first(where: { $0.name == senderName }) else {
        // User not found
        return
    }

    self.receiveMessage(fromSender: sender, message: message)
}

func receiveMessage(fromSender sender: User, message: String) {
    do {
        let session = try self.chat.loadUpSession(
            withParticipantWithCard: sender.card, message: message)

        // decrypt message using established session
        let plaintext = try session.decrypt(message)

        // show a message to the user
        print(plaintext)
    }
    catch {
        // Error handling
    }
}

// generate a new Virgil Key
let aliceKey = virgil.keys.generateKey()

// save the Virgil Key into storage
try! aliceKey.store(withName: @"[KEY_NAME]",
  password: @"[KEY_PASSWORD]")

// create identity for Alice
let aliceIdentity = virgil.identities.
  createUserIdentity(withValue: "alice", type: "name")

// create a Virgil Card
var aliceCard = try! virgil.cards.
  createCard(with: aliceIdentity, ownerKey:aliceKey)

// export a Virgil Card to string
let exportedCard = aliceCard.exportData()

// transmit the Virgil Card to the server and receive response
let cardData = TransmitToServer(exportedCard)