In spite of a legal framework having been in place for many years now, the market share of qualified electronic signatures is still low. New designs are desperately needed for qualified electronic signature to flourish. Cloud computing provides a new and promising opportunity for delivering electronic signatures as a service. This paper covers the challenges in implementing a cloud-based digital signature service and, as a result, outlines cloud (Signing Cloud) that performs digital signature. This study also refers to the on-going work on rationalized European digital signature standardization framework, related to mandate M/460, issued by the European Commission.