Proof of Possession for Cloud Storage via Lagrangian Interpolation Techniques
         
                        L. Krzywiecki,   M.Kutylowski
		      Wroclaw University of Technology
         
We consider provable data possesion (PDP) - a protocol which enables an owner of data stored
in the cloud to verify whether this data is still available in the cloud  without holding a copy 
of the file. 

We propose a  framework for PDP built on top of Lagrangian interpolation in the exponent 
for groups with hard discrete logarithm problem.  We reuse properties of this arithmetic 
exploited so far in broadcast encryption systems. The scheme uses short challenges and requests 
as well as quite standard algebraic systems and operations.  


Keywords:
provable data possession, cloud computing,  Lagrangian interpolation  in the exponent, broadcast encryption