Fixed correct conversion to byte arrays in android attestation.

Author: KristofferStrube

samples/KristofferStrube.Blazor.WebAuthentication.API/WebAuthenticationAPI.cs

@@ -114,7 +114,7 @@ public static Results<Ok, BadRequest<string>> Register(string userName, [FromBod
                 string attestationStatementValiditiyJsonString = Base64UrlEncoder.Decode(base64EncodedattestationStatementValiditiyJsonString);
                 AttestationStatementValiditiy attestationStatementValiditiy = JsonSerializer.Deserialize<AttestationStatementValiditiy>(attestationStatementValiditiyJsonString);
 
-                var concattedAuthenticatorAndClientData = Encoding.UTF8.GetBytes(registration.Response.AuthenticatorData).Concat(Encoding.UTF8.GetBytes(registration.Response.ClientDataJSON)).ToArray();
+                var concattedAuthenticatorAndClientData = Convert.FromBase64String(registration.Response.AuthenticatorData).Concat(Convert.FromBase64String(registration.Response.ClientDataJSON)).ToArray();
 
                 var hasher = SHA256.Create();
                 var hash = hasher.ComputeHash(concattedAuthenticatorAndClientData);