Acknowledgements

This material is based upon work supported by the National Science Foundation under grant numbers 0850557, 0943633, 1053575, 1440609, 1547268, and 1548562 and by the Department of Energy under award number DE-SC0008597. CILogon operations are supported by subscribers.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the United States Government or any agency thereof.