Crypto Recipes

If it isn't documented here, there's a very good chance it is still available in the library. The documentation below is incomplete.

Create a buffer filled with cryptographically strong random data

// WinRT-like API
uint length = 15;
byte[] cryptoRandomBuffer = WinRTCrypto.CryptographicBuffer.GenerateRandom(length);

// .NET Framework-like API
byte[] cryptoRandomBuffer = new byte[15];
NetFxCrypto.RandomNumberGenerator.GetBytes(cryptoRandomBuffer);

Generate a random number

uint random = WinRTCrypto.CryptographicBuffer.GenerateRandomNumber();
uint randomFrom0To15 = WinRTCrypto.CryptographicBuffer.GenerateRandomNumber() % 16;

Derive a symmetric key from a password

To use crypto APIs with a user-supplied password, you must at least convert the password into a byte buffer. But it's more secure to run it through a key derivation algorithm, using this technique:

string password; // comes in from the user.
byte[] salt; // best initialized to a unique value for each user, and stored with the user record
int iterations = 5000; // higher makes brute force attacks more expensive
int keyLengthInBytes;
byte[] key = NetFxCrypto.DeriveBytes.GetBytes(password, salt, iterations, keyLengthInBytes);

// A similar technique is possible using WinRT-emulated API via the `WinRTCrypto.KeyDerivationAlgorithmProvider`.

Get the hash for a buffer (SHA1, SHA256, etc.)

byte[] data;
var hasher = WinRTCrypto.HashAlgorithmProvider.OpenAlgorithm(HashAlgorithm.Sha1);
byte[] hash = hasher.HashData(data);
string hashBase64 = Convert.ToBase64String(hash);

Get the MAC for a buffer (HMAC-SHA1, HMAC-SHA256, etc.)

byte[] keyMaterial;
byte[] data;
var algorithm = WinRTCrypto.MacAlgorithmProvider.OpenAlgorithm(MacAlgorithm.HmacSha1);
CryptographicHash hasher = algorithm.CreateHash(keyMaterial);
hasher.Append(data);
byte[] mac = hasher.GetValueAndReset();
string macBase64 = Convert.ToBase64String(mac);

Perform AES encryption/decryption

byte[] keyMaterial;
byte[] data;
var provider = WinRTCrypto.SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithm.AesCbcPkcs7);
var key = provider.CreateSymmetricKey(keyMaterial);
byte[] iv = null; // this is optional, but must be the same for both encrypting and decrypting
byte[] cipherText = WinRTCrypto.CryptographicEngine.Encrypt(key, data, iv);
byte[] plainText = WinRTCrypto.CryptographicEngine.Decrypt(key, cipherText, iv);