Continuous authentication utilizes automatic recognition of certain user features for seamless and passive authentication without requiring user attention. Such features can be divided into categories of physiological biometrics and behavioral biometrics. Keystroke dynamics is proposed for behavioral biometrics-oriented authentication by recognizing users by means of their typing patterns. However, it has been pointed out that continuous authentication using physiological biometrics and behavior biometrics incur privacy risks, revealing personal characteristics and activities. In this paper, we consider a previously proposed keystroke dynamics-based authentication scheme that has no privacy-preserving properties. In this regard, we propose a generic privacy-preserving version of this authentication scheme in which all user features are encrypted -- preventing disclosure of those to the authentication server. Our scheme is generic in the sense that it assumes homomorphic cryptographic primitives. Authentication is conducted on the basis of encrypted data due to the homomorphic cryptographic properties of our protocol.