1. Verifiable Cloud Computing KANG Yu

2. Verifiable Computation Weak clients Computationally powerful cloud Goal: – Verify the computing result

3. Non-Interactive Verifiable Computing By Gennaro et al. Enables a outsourcing computation of a non- interactive function on untrusted workers

4. Non-Interactive Verifiable Computing Key idea: – Take advantage of Yao’s Garbled Circuit Construction. – Overcome the one-time construction by fully- homomorphic Encryption Verify the computation as well as keep the privacy. But stays theoretical.

5. Verifiable Computation with Two or More Clouds By Canetti et al. Use two or more clouds to perform computation and find one to trust

6. Verifiable Computation with Two or More Clouds Key idea: – Assume at least one of clouds is honest – Use efficient-players Refereed Games (epRG) model – Take advantage of Merkle Hash Tree on constructing reduced-configuration Turing Machine – The referee do a binary search on steps to computing Can be implemented but need at least two clouds.

7. Monitoring Remotely Executing Programs By Yang et al. Complier techniques produce codes with beacons On periodically exchange beacons to trace the progress and recompute some results to check the correctness of remotely executing program

8. Monitoring Remotely Executing Programs Key idea: – Create finite state machine for source code and create beacons for computationally significant method – Location beacon for tracking the progress – Recomputation beacons for checking the validity of computation Can be implemented but it trust the cloud provider’s infrastructure.

9. Verifying Cloud-Hosted Web Applications By Jana et al. Verify the correctly executing of cloud-hosted web applications with help of a subset of users

10. Verifying Cloud-Hosted Web Applications Key idea: – Model web applications operations as reads and writes to an object store, verify whether an object store is consistent – Assume there are a subset of users keep logs that can be accessed – Doing collaboration verification by checking the consistency of logged reads and writes Can be implemented but the model may be limited by ignoring computation.

11. Conclusion Four different verification approaches Different situation Trusted Platform Module (TPM) may be useful Cloud: totally untrustable or not

12. References Rosario Gennaro, Craig Gentry, Bryan Parno, Non-interactive verifiable computing: outsourcing computation to untrusted workers, Proceedings of the 30th annual conference on Advances in cryptology, August 15-19, 2010 Ran Canetti, Ben Riva, and Guy N. Rothblum, Verifiable computation with two or more clouds, Workshop on Cryptography and Security in Clouds, 2011

13. References Shuo Yang, Ali R. Butt, Y. Charlie Hu, Samuel P. Midkiff, Trust but verify: monitoring remotely executing programs for progress and correctness, Proceedings of the tenth ACM SIGPLAN symposium on Principles and practice of parallel programming, June 15-17, 2005 Suman Jana and Vitaly Shmatikov, EVE: Verifying Correct Execution of Cloud-Hosted Web Applications, USENIX Workshop on Hot Topics in Cloud Computing, 2011

14. Q&A?