public static async Task AddCardAsync(StarbucksCard card)
{
var cards = await LoadCardsAsync();
if (cards.Contains(card))
{
return;
}
cards.Add(card);
await SaveCards(cards);
}
public static async Task UpdateCardAsync(StarbucksCard card)
{
var cards = await LoadCardsAsync();
var cardToUpdate = cards.FirstOrDefault(x => x == card);
if (cardToUpdate == null)
{
return;
}
cardToUpdate.AccountNumber = card.AccountNumber;
cardToUpdate.ScannedData = card.ScannedData;
cardToUpdate.Title = card.Title;
await SaveCards(cards);
}
public static async Task <ObservableCollection <StarbucksCard> > LoadCardsAsync()
{
var decryptedCards = new ObservableCollection <StarbucksCard>();
if (!RoamingSettings.Values.ContainsKey("StarbucksCards"))
{
return(decryptedCards);
}
if (RoamingSettings.Values.TryGetValue("StarbucksCards", out var storedValue))
{
var protectedCards = (ObservableCollection <StarbucksCard>)storedValue;
foreach (var protectedCard in protectedCards)
{
var decryptedCard = new StarbucksCard
{
Title = protectedCard.Title
};
// Decrypt account/card number
IBuffer protectedAcctNumberBuffer = System.Text.Encoding.UTF8.GetBytes(protectedCard.AccountNumber.ToString()).AsBuffer();
var unprotectedAcctNumberBuffer = await new DataProtectionProvider().UnprotectAsync(protectedAcctNumberBuffer);
var acctNumClearText = CryptographicBuffer.ConvertBinaryToString(BinaryStringEncoding.Utf8, unprotectedAcctNumberBuffer);
decryptedCard.AccountNumber = Convert.ToInt64(acctNumClearText);
// Decrypt scan data
IBuffer protectedScanDataBuffer = System.Text.Encoding.UTF8.GetBytes(protectedCard.ScannedData).AsBuffer();
var unprotectedScanDataBuffer = await new DataProtectionProvider().UnprotectAsync(protectedScanDataBuffer);
var scanDataClearText = CryptographicBuffer.ConvertBinaryToString(BinaryStringEncoding.Utf8, unprotectedScanDataBuffer);
decryptedCard.ScannedData = scanDataClearText;
// Add the card to runtime list
decryptedCards.Add(decryptedCard);
}
}
return(decryptedCards);
}
public static async Task SaveCards(ObservableCollection <StarbucksCard> unprotectedCards)
{
var protectedCards = new ObservableCollection <StarbucksCard>();
foreach (var unprotectedCard in unprotectedCards)
{
var protectedCard = new StarbucksCard
{
Title = unprotectedCard.Title
};
// encrypt card number at rest
var numberData = CryptographicBuffer.ConvertStringToBinary(unprotectedCard.AccountNumber.ToString(), BinaryStringEncoding.Utf8);
var numberDataProtected = await new DataProtectionProvider().ProtectAsync(numberData);
protectedCard.AccountNumber = Convert.ToInt64(numberDataProtected);
// encrypt scanned data at rest
var scanData = CryptographicBuffer.ConvertStringToBinary(unprotectedCard.ScannedData, BinaryStringEncoding.Utf8);
var scanDataProtected = await new DataProtectionProvider().ProtectAsync(scanData);
protectedCard.ScannedData = Convert.ToString(scanDataProtected);
}
RoamingSettings.Values["StarbucksCards"] = JsonConvert.SerializeObject(protectedCards);
}
public CardEditViewModel()
{
Card = new StarbucksCard {
Title = "", AccountNumber = 1234123412341234, ScannedData = "Notes"
};
}
