Converting a byte array to string and then back again produced different results

Question

I\'m using the .net port of libsodium. The hash generation function has two forms, one that accepts byte arrays and one that accepts strings:

public static b         


        

Answer 1

Converting a byte array to string and then back again produced different results

A binary data may not be converted to string and then back to byte array using Encoding.[AnyEncoding].GetBytes and Encoding.[AnyEncoding].GetString

Instead use Convert.ToBase64String and Convert.FromBase64String

You can easily test...

var bytes = new byte[] { 255, 255, 255 }; 
var buf = Encoding.UTF8.GetString(bytes);
var newbytes = Encoding.UTF8.GetBytes(buf);

newbytes's length will be 9.....

Edit: This is the test case for @Theo

var bytes = new byte[] { 0, 216 }; //any new byte[] { X, 216 };
var buf = Encoding.Unicode.GetString(bytes);
var newbytes = Encoding.Unicode.GetBytes(buf); //253,255

Answer 2

I think the problem here is that the ArgonGenerateSalt method doesn't return a UTF8 encoded string, it returns completely random bytes.

You can't decode random bytes as a UTF8 string and expect it to round trip. A trivial example to see where this blows up is to do the following:

var data = new byte[] { 128 };
var dataAsString = Encoding.UTF8.GetString( data );
var dataAsBytes = Encoding.UTF8.GetBytes( dataAsString );

After this, dataAsBytes will be 3 bytes (specifically 239, 191, 189).