Entity Framework + MySQL: BLOB/TEXT column 'Hash' used in key specification without a key length

I'm trying to use Entity Framework with MySQL. I've just installed MySQL Installer for Windows which includes MySQL Connector for .NET.

I can't find any documentation on how to actually use this thing, so I've been cobbling pieces together from various tutorials. It appears I need the references for MySql.Data and MySql.Data.Entity for EF6 (screenshot).

Then I stole this source code from some random project which is the only reference I could find to MySqlConnectionFactory:

class ImgSigDbConfig : DbConfiguration
{
    public ImgSigDbConfig()
    {
        base.AddDependencyResolver(new MySqlDependencyResolver());
        base.SetProviderFactory(MySqlProviderInvariantName.ProviderName, new MySqlClientFactory());
        base.SetProviderServices(MySqlProviderInvariantName.ProviderName, new MySqlProviderServices());
        base.SetDefaultConnectionFactory(new MySqlConnectionFactory());
        base.SetMigrationSqlGenerator(MySqlProviderInvariantName.ProviderName, () => new MySqlMigrationSqlGenerator());
        base.SetProviderFactoryResolver(new MySqlProviderFactoryResolver());
        base.SetManifestTokenResolver(new MySqlManifestTokenResolver());
    }
}

I couldn't figure out how to set my database credentials anywher ein there, but apparently you can pass them in when constructing the DbContext:

Database.SetInitializer(new DropCreateDatabaseIfModelChanges<ImgSimContext>());

var conn = new MySqlConnectionStringBuilder
{
    Server = "localhost",
    UserID = "root",
    Password = "pass",
    Database = "ImgSig"
};


using (var db = new ImgSimContext(conn.ToString()))
{
    SqlConnection.ClearAllPools();
    db.Database.Initialize(force: true);

Now I've created a very simple POCO:

internal class ImgSig
{
    [Key, Required]
    public int Id { get; set; }

    [Index, StringLength(16), Required]
    public byte[] Hash { get; set; }
}

But when it hits db.Database.Initialize an exception is thrown:

BLOB/TEXT column 'Hash' used in key specification without a key length

Which makes perfect sense because in MySQL you have to set the key length for any blob/text fields (although it would be nice to see what SQL it's trying to run).

So my questions are:

1. How can I change the data type of Hash to a fixed length binary(16)?
2. How can I set the key length (preferably using attributes)?