/// <summary>
/// Decrypts a string.
/// </summary>
/// <param name="userScope">
/// true if the string should only be decryptable by the current user, false if the string should
/// only be decryptable by any user on the local machine.
/// </param>
/// <param name="cipherText"> The string to decrypt (binary data in BASE64 format). </param>
/// <param name="additionalEntropy"> Any used additional entropy or salt (can be null). </param>
/// <returns>
/// The decrypted plain text string or null if <paramref name="cipherText" /> is null.
/// </returns>
/// <exception cref="CryptographicException"> The decryption failed. </exception>
/// <exception cref="ArgumentException"> <paramref name="cipherText" /> is not in BASE64 format. </exception>
public static string Decrypt(bool userScope, string cipherText, string additionalEntropy = null)
{
if (cipherText == null)
{
return(null);
}
byte[] encryptedBytes;
try
{
encryptedBytes = Convert.FromBase64String(cipherText);
}
catch (FormatException exception)
{
throw new ArgumentException("The cipher text is not in BASE64.", nameof(cipherText), exception);
}
byte[] additionalEntropyBytes = LocalEncryption.GetAdditionalEntropyBytes(additionalEntropy);
byte[] plainBytes = ProtectedData.Unprotect(encryptedBytes, additionalEntropyBytes,
userScope ? DataProtectionScope.CurrentUser
: DataProtectionScope.LocalMachine);
string plainText = LocalEncryption.StringEncoding.GetString(plainBytes);
return(plainText);
}
/// <summary>
/// Encrypts a string.
/// </summary>
/// <param name="userScope">
/// true if the string should only be decryptable by the current user, false if the string should
/// only be decryptable by any user on the local machine.
/// </param>
/// <param name="plainText"> The plain text string to encrypt. </param>
/// <param name="additionalEntropy"> Any used additional entropy or salt (can be null). </param>
/// <returns>
/// The encrypted string (binary data in BASE64 format) or null if <paramref name="plainText" /> is null.
/// </returns>
/// <exception cref="CryptographicException"> The encryption failed. </exception>
public static string Encrypt(bool userScope, string plainText, string additionalEntropy = null)
{
if (plainText == null)
{
return(null);
}
byte[] additionalEntropyBytes = LocalEncryption.GetAdditionalEntropyBytes(additionalEntropy);
byte[] plainBytes = LocalEncryption.StringEncoding.GetBytes(plainText);
byte[] encryptedBytes = ProtectedData.Protect(plainBytes, additionalEntropyBytes,
userScope ? DataProtectionScope.CurrentUser
: DataProtectionScope.LocalMachine);
string encryptedText = Convert.ToBase64String(encryptedBytes);
return(encryptedText);
}