/// <summary>
/// Computes a cryptographically secure random Kademlia key that matches the boundaries of this <see cref="IBucket"/>.
/// </summary>
/// <returns></returns>
public static string GetRandomKey(string key, int index)
{
byte[] keyBytes = EncryptionProvider.GetBytes(key);
byte[] bytes = GetRandomKey();
int sharedPrefixLengthBytes = (int)Math.Floor((index / (decimal)8));
int sharedPrefixLengthBits = index % 8;
CryptoRandom cryptoRandom = new CryptoRandom();
for (int i = 0; i < keyBytes.Length; i++)
{
if (i > sharedPrefixLengthBytes)
{
// Keep randomness
bytes[i] = (byte)(bytes[i] ^ keyBytes[i]);
}
else if (i < sharedPrefixLengthBytes)
{
// Use the bytes from the given key
bytes[i] = keyBytes[i];
}
else if (i == sharedPrefixLengthBytes)
{
// Preserve some random bits without modifying the most significant bit index
int min = (255 >> (sharedPrefixLengthBits + 1)) + 1;
int max = (255 >> sharedPrefixLengthBits) + 1;
int shift = cryptoRandom.Next(min, max);
bytes[i] = (byte)(shift ^ keyBytes[i]);
}
}
return(EncryptionProvider.GetString(bytes));
}
/// <summary>
/// Generates a <see cref="IContact"/> for a node.
/// </summary>
/// <returns></returns>
public static IContact GetContact()
{
if (_contact != null)
{
return(_contact);
}
Config config = Config.ReadConfig();
string nodeId = config.Kademlia.NodeId;
if (!string.IsNullOrEmpty(nodeId))
{
return(new Contact(Transport.GetServiceBaseUrl(), nodeId));
}
string publicIp = EnvironmentHelper.GetPublicIp();
string localIp = EnvironmentHelper.GetLocalIp();
string machineName = EnvironmentHelper.GetFqdn();
FileInfo assemblyFileInfo = AssemblyHelper.GetEntryAssemblyFileInfo();
string directory = assemblyFileInfo.DirectoryName;
string applicationId = AppSettings.InstanceMode == InstanceMode.Single ?
AssemblyHelper.GetEntryAssemblyId() :
EncryptionProvider.GetString(GetRandomKey());
string uniqueAttributes = string.Format("{0}#{1}#{2}#{3}#{4}", publicIp, localIp, machineName, directory, applicationId);
nodeId = EncryptionProvider.Hash(uniqueAttributes);
return(_contact = new Contact(Transport.GetServiceBaseUrl(), nodeId));
}