Cloud-based signing solutions are on the rise and attempt to revolutionize business processes while integrating themselves well into cloud storage infrastructures. The combination promises faster process flows for signing a contract than the classic paper-based approach. In this survey we reviewed seven representative examples of cloud-based signature services and assessed them at the provided cryptographic features, the interfaces they offer, the authentication methods they provide and the key storage implementations used. We found that multi-factor authentication and hardware security module back-ends are common features. Interfaces range from APIs over web user interfaces to proprietary applications. Yet, there are shortcomings in flexibility and security.