// Strings are very unsafe to store passwords, or keys in. This is because strings in .NET will always be subject to garbage collection
// which means they can always be dumped out of memory onto disk through various methods, and exploits. However, especially when dealing
// with website logins through forms. It's almost impossible to avoid the risk completely. Below are some examples of best dealing with
// these conditions. Ultimately however, if you can record your secure input directly in byte, char, or SecureString you will always be better off.
public static void Poly()
{
using var poly = new Poly1305(new PinnedMemory <byte>(new byte[] { 63, 61, 77, 20, 63, 61, 77 }, false));
using var hash = new PinnedMemory <byte>(new byte[poly.GetLength()]);
var unsafeCaw = "caw caw caw"; // this is unsafe because string's can't be pinned and are subject to garbage collection, and being written to disk (pagefile).
var caw = new PinnedMemory <byte>(Encoding.UTF8.GetBytes(unsafeCaw), false); // this is now safe but ONLY the variable caw, unsafeCaw is STILL exposed.
unsafeCaw = string.Empty; // unsafeCaw COULD STILL exposed even tho we set it to empty because this depends on garbage collection getting around to clearing it.
poly.UpdateBlock(caw, 0, caw.Length);
poly.DoFinal(hash, 0);
Console.WriteLine(BitConverter.ToString(hash.ToArray()));
// This is a more uncommon but should be safer example of how to use strings with SecureString for input.
using var exampleHash2 = new PinnedMemory <byte>(new byte[poly.GetLength()]);
var secureCaw = new SecureString();
secureCaw.AppendChar('c');
secureCaw.AppendChar('a');
secureCaw.AppendChar('w');
secureCaw.AppendChar(' ');
secureCaw.AppendChar('c');
secureCaw.AppendChar('a');
secureCaw.AppendChar('w');
secureCaw.AppendChar(' ');
secureCaw.AppendChar('c');
secureCaw.AppendChar('a');
secureCaw.AppendChar('w');
secureCaw.MakeReadOnly();
using var pinnedCaw = new PinnedMemory <char>(new char[secureCaw.Length]);
var cawPointer = Marshal.SecureStringToBSTR(secureCaw);
for (var i = 0; i <= secureCaw.Length - 1; i++)
{
var c = (char)Marshal.ReadByte(cawPointer, i * 2);
pinnedCaw[i] = c;
}
using var pinnedCawBytes = new PinnedMemory <byte>(Encoding.UTF8.GetBytes(pinnedCaw.ToArray()), false);
poly.UpdateBlock(pinnedCawBytes, 0, secureCaw.Length);
poly.DoFinal(exampleHash2, 0);
Console.WriteLine(BitConverter.ToString(exampleHash2.ToArray()));
}
public static void Poly()
{
using var poly = new Poly1305(new PinnedMemory <byte>(new byte[] { 63, 61, 77, 20, 63, 61, 77 }, false));
using var hash = new PinnedMemory <byte>(new byte[poly.GetLength()]);
// digest.UpdateBlock(new byte[] {63, 61, 77, 20, 63, 61, 77, 20, 63, 61, 77}, 0, 11); // This may be exposed without being pinned.
poly.UpdateBlock(new PinnedMemory <byte>(new byte[] { 63, 61, 77, 20, 63, 61, 77, 20, 63, 61, 77 }, false), 0, 11);
poly.DoFinal(hash, 0);
Console.WriteLine(BitConverter.ToString(hash.ToArray()));
}