Truly Efficient String Oblivious Transfer Using Resettable Tamper-Proof-Tokens

Current SFE techniques require expensive public key operations for each input bit of the function. This cost can be avoided by using tamper-proof hardware. However, current (efficient) techniques require the token to be resistant to reset or duplication. We propose a new truly efficient String Oblivious Transfer (OT) technique relying on weaker {em resettable} tamper-proof token. This results in new more efficient SFE protocols which completely avoid public key operations. Our OT is secure against covert sender and malicious receiver. If the token is semi-honest (e.g. if it is provided by a trusted entity, but adversarily initialized), then our protocol is secure against malicious adversaries in concurrent execution setting. Only one party is required to provide the token, which makes it appropriate for typical asymmetric client-server scenarios (banking, TV, Service Providers, etc.)