Derivation cryptographic keys from human biometrics opens a new promising research area when it can be used efficiently for not only verification or recognition tasks, but also symmetric-key based applications. Among existing biometric traits, face is considered as the most popular biometrics since facial features are informative and discriminative. In this paper, we present a comprehensive survey of Face-based key generation (FKGS). First, we summarize the trend of FKGS researches and sum up the methods which play important roles in the proposed key generation systems. Then we present the evaluation and the general performance analysis; from that, we give a discussion about the advantages and disadvantages of surveyed studies to clarify the fundamental requirements and the main challenges when implementing FKGS in practice. Finally, an outlook on future prospects is given