gistfile1.cs

...

   DocumentStore = new EmbeddableDocumentStore
   {
        Configuration =
            {
                Catalog = { Catalogs = { new TypeCatalog(typeof(FixedPasswordAuthenticateClient)) } },
                AuthenticationMode = "oauth",
                OAuthTokenCertificate = CertGenerator.GenerateNewCertificate("MyApp"),
                OAuthTokenServer = "http://localhost:8080/OAuth/AccessToken",
            },
   };

...

    public class FixedPasswordAuthenticateClient : IAuthenticateClient
    {
        private string _passwordHash;

        public FixedPasswordAuthenticateClient(string passwordHash)
        {
            _passwordHash = passwordHash;
        }

        public bool Authenticate(DocumentDatabase documentDatabase, string username, string password,
            out AccessTokenBody.DatabaseAccess[] allowedDatabases)
        {
            allowedDatabases = new[]
            {
                new AccessTokenBody.DatabaseAccess
                {
                    TenantId = "*"
                },
            };

            if (!String.IsNullOrEmpty(password))
            {
                using (var sha = SHA256.Create())
                {
                    return PasswordHash == Convert.ToBase64String(sha.ComputeHash(Encoding.Unicode.GetBytes(password)));
                }
            }
            return false;
        }
    }