I have to store user credentials in a web api somewhere. I decided I create a console application in the solution, next to the Web API, that encrypts the data, and writes it to the web api’s appsettings.json.
Here is the relevant code:

var serviceCollection = new ServiceCollection();
serviceCollection.AddDataProtection(o =>
{
    o.ApplicationDiscriminator = CoreVariables.SALT;
}
).SetApplicationName("test");

var services = serviceCollection.BuildServiceProvider();

var dataProtector = services.GetRequiredService<IDataProtectionProvider>();
var protector = dataProtector.CreateProtector(CoreVariables.DATA_PROTECTION_REASON);

//Fill username and password, REMOVE AFTER ENCRYPTION, DONT PUSH IT TO REPOSITORY
string username = "";
string password = "";

if (string.IsNullOrEmpty(username))
{
    throw new Exception("Username cannot be null or empty.");
}

if (string.IsNullOrEmpty(password))
{
    throw new Exception("Username cannot be null or empty.");
}

string protectedUsername = protector.Protect(username);
string protectedPassword = protector.Protect(password);

string appsettingsFilePath =
    Path.Combine(Directory.GetParent(Directory.GetCurrentDirectory()).Parent.Parent.Parent.FullName,
        "My.API", "appsettings.json");

if (!File.Exists(appsettingsFilePath))
{
    throw new Exception($"Cannot find file in path: {appsettingsFilePath}");
}

var appsettingsContent = File.ReadAllText(appsettingsFilePath);
var appsettingsJson = JsonConvert.DeserializeObject<Dictionary<string, object>>(appsettingsContent);
appsettingsJson["User"] = protectedUsername;
appsettingsJson["Secret"] = protectedPassword;
appsettingsJson["SecretLastChanged"] = DateTime.Now.ToString();
var updatedJson = JsonConvert.SerializeObject(appsettingsJson, Formatting.Indented);
File.WriteAllText(appsettingsFilePath, updatedJson);

Then, when I deploy the application, I got an exception, saying The key was not found in the key ring.

Here is the relevant code from the API:

Program.cs:

builder.Services.AddDataProtection(o => {
        o.ApplicationDiscriminator = CoreVariables.SALT;
        
    }
).SetApplicationName("test");

Service, where I use it:

 public MyService(IDataProtectionProvider provider)
 {
     _protector = provider.CreateProtector(CoreVariables.DATA_PROTECTION_REASON);
 }

 public async Task<string> Authentication(string userName, string password)
 {
     string authUsername = _protector.Unprotect(userName);
     string authPassword = _protector.Unprotect(password);
 }

Does this encryption is somehow connected to computer data? When I deploy the application into a server, the decryption will not work.