/// <summary>
/// Decrypts the <see cref="FileIndex"/> data structure contained in the given <see cref="EncryptedPacket"/>.
/// </summary>
/// <param name="encryptedPacket">The encrypted data to decrypt the <see cref="FileIndex"/> from.</param>
/// <param name="archiveKey">The key used for decryption.</param>
/// <param name="securitySettings">The <see cref="SecuritySettings"/> for the secure archive.</param>
/// <returns>The decrypted <see cref="FileIndex"/>.</returns>
public static FileIndex DecryptFrom(
EncryptedPacket encryptedPacket,
ArchiveKey archiveKey,
SecuritySettings securitySettings)
{
var indexEntries = JsonHelpers.DecryptAndDeserialize <List <FileIndexEntry> >(
encryptedPacket,
archiveKey,
securitySettings);
return(new FileIndex(indexEntries));
}