dpapi-test.linq

<Query Kind="Statements">
  <Reference>&lt;RuntimeDirectory&gt;\System.Security.dll</Reference>
  <Namespace>System.Security.Cryptography</Namespace>
</Query>

var scope = DataProtectionScope.CurrentUser;

var data = Encoding.UTF8.GetBytes("hello, world (privately)");

var encrypted = ProtectedData.Protect(data, null, scope);
BitConverter.ToString(encrypted).Dump("encrypted");

var decrypted = ProtectedData.Unprotect(encrypted, null, scope);
Encoding.UTF8.GetString(decrypted).Dump("decrypted");

var tampered = encrypted.ToArray();
tampered[encrypted.Length - 1] = 0xff;
ProtectedData.Unprotect(tampered, null, scope); // throws CryptographicException