Cryptography from Sunspots: How to Use an Imperfect Reference String

The Common Reference String (CRS) model equips all protocol participants with a common string that is sampled from a pre-specified distribution, say the uniform distribution. This model enables otherwise-impossible cryptographic goals such as removing interaction from protocols and guaranteeing composable security. However, knowing the precise distribution of the reference string seems crucial for all known protocols in this model, in the sense that current security analyses fail when the actual distribution of the reference string is allowed to differ from the specified one even by a small amount. This fact rules out many potential implementations of the CRS model, such as measurements of physical phenomena (like sunspots), or alternatively using random sources that might be adversarially influenced. We study the possibility of obtaining universally composable (UC) security in a relaxed variant of the CRS model, where the reference string it taken from an adversarially specified ...

• Type: Conference
• Year: 2007
• Where: FOCS
• Authors: Ran Canetti, Rafael Pass, Abhi Shelat
• Keywords: Common Reference String, CRS Model, FOCS 2007, Reference String, Theoretical Computer Science