Adaptive Concurrent Non-Malleability with Bare Public-Keys

Concurrent non-malleability (CNM) is central for cryptographic protocols running concurrently in environments such as the Internet. In this work, we formulate CNM in the bare public-key (BPK) model, and show that round-efficient concurrent non-malleable cryptography with full adaptive input selection can be established, in general, with bare public-keys (where, in particular, no trusted assumption is made). Along the way, we clarify the various subtleties of adaptive concurrent nonmalleability in the bare public-key model. The work described in this paper was supported in part by the National Basic Research Program of China Grant (973) 2007CB807900, 2007CB807901, and by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project Number CityU 122105) and CityU Research Grant (9380039). The third author is also supported by NSFC (No. 60703091), the Pu-Jiang and Qi-Ming-Xing Programs of Shanghai and a grant from MSRA. Institute for Theoretical Computer Science (ITCS), Tsinghua University, Beijing, China. [email protected] Google Inc. and Columbia University, New York, NY, USA. [email protected] Contact author. Software School, Fudan University, Shanghai 200433, China. [email protected] Works partially done while visiting Tsinghua university and City University of Hong Kong.