Split-and-Delegate: Threshold Cryptography for the Masses

Abstract

Threshold Cryptography (distributed key splitting) is traditionally employed as means to preserve the whole key against compromise, i.e., for risk reduction (coping with memory compromise) and availability (coping with denial of service). Recently, some functionality of splitting keys has been shown to be useful beyond preservation, yielding a small number of high-security, server-related applications. However, the business applications and market applicability of splitting keys is still not realized or analyzed. The goal of this position paper is to put forth the thesis that the full power of threshold cryptography as a useful and attractive tool is going to be unleashed only if the ability to split keys is given to end users (the masses). More specifically, we claim that threshold cryptographic operations (e.g. splitting a key) together with user capability to delegate (which we view as a necessary extension of PKI) should be part of the suite of operations available to end-users of a PKI (e.g., embe dded in user crypto-APIs / user smartcards). This new tool (“split and delegate”) will enable flexible key management at the user level, in contrast with the traditional rigidity of PKI. We note that threshold cryptography is currently mainly an idea and still not in the market (though some companies do offer split key in hardware or software). We believe that the economic value of the suggested user-based applications will be the central driving force behind any market adoption of threshold cryptography. We give an analysis of the potential business and of market penetration scenarios (such business analysis of suggested new cryptographic applications is often done but rarely published).