Burdens of Proof: Cryptographic Culture and Evidence Law in the Age of Electronic Documents

Conclusion

182 Chapter 7 rion of “unplugged cryptography” into the single design objective of simplicity: cryptographic protocols should exhibit both ease of implementation and understanding, and parties to them “should be required to expend only a small amount of time, energy, and money to learn, use, and be confident in the protocol.”66 The paper was motivated by a real-life situation: during a conversation, two managers at a company realize they both have received confidential complaints about the same sensitive matter. In confiding to each other, they face a dilemma: if the complaints originate from two different individuals, their privacy will have been compromised. Cryptographers have developed sophisticated protocols for this problem of “secret function evaluation.”67 Such protocols would allow the managers to carry this type of conversation over electronic networks, without relying on any trusted third parties, with mathematical guarantees that their conversation will not leak any information whatsoever. Such guarantees come at a cost however: the protocols “are complex schemes that only certain experts can be expected to understand. Thus, blind trust is given to the system designer. An additional point is that these solutions are not yet genuinely practical, even if implemented with the best possible care. Our goal in this article is to provide some schemes whose implementation is so transparent that no expertise is needed to verify correctness. We hope that some of these schemes will provide not only practical solutions to our problem, but also insight into the subtleties of communication and information.”68 Fagin, Naor, and Winkler eventually come up with fourteen different solutions for the managers’ problem, with different trade-offs between design criteria.69 The last solution is provided by the first author’s thirteenyear -old son, who wonders why the managers can’t simply inquire directly to the complaining parties. Indeed, in the end, this will be the solution that the managers adopt to resolve their conundrum. Conclusion The controversies and research projects outlined in this chapter point to an intriguing dynamic. Although modern cryptography sought to ground its practices in abstract mathematical worlds of binary information, number theory, and computational complexity, several material phenomena made The Cryptographic Imagination 183 a claim for their relevance to these practices. Hash functions, electromagnetic radiation, the human perceptual system, sealed envelopes, and the cognitive capabilities of users requested—with varying degrees of urgency— that they be included in the deliberations. In response, the standard model that has informed much cryptographic work in the Diffie-Hellman era has been extended to include random oracles, the physical leakage of power, users’ visual acuity, and the security properties of scratch-cards. Engaging with the inescapable materiality of information does not signify some kind of demotion or regression. Instead, it suggests that what perhaps best characterizes cryptographic practice is not an inevitable ascension to mathematics, but rather ingenuity, playfulness, and pragmatism in its devotion to achieving (and defeating) counterintuitive communication goals. Over the course of history, this ingenuity has consistently taken advantage of the material properties of physical media, of the logical properties of information encoding, and of their mutual interactions in the service of these goals. I propose an engagement with the material world offers in fact important benefits. Taking advantage of the embodied capabilities of human beings (memory, perception, cognition) and of the cultural and institutional familiarity of pen-and-paper technologies (books, paper, envelopes) may provide multiple pathways to broader social acceptance of cryptographic design goals. Not only does embracing the material world offer rich sources of inspiration for design, but it also enables more complex strategies of technology adoption than the “build it and they will come” philosophy that has so far implicitly driven the efforts of the community. Rather than emphasizing its radical discontinuity with the paper-and-ink world, cryptographic design can draw from existing cultural practices and technological infrastructures as resources. Such an approach would directly enhance the abilities of cryptographic technologies to suture themselves into the existing social fabric, on multiple levels—cognitively, materially, institutionally. In The Languages of Edison’s Light, Charles Bazerman argued that a key to Edison’s commercial successes laid precisely in his skill at negotiating the boundaries of tradition and invention: “Despite the great changes that came in the wake of the new technology, incandescent light and power had first to be built on historical continuities of meaning and value. It had to take a place within the discourse and the representational meaning [3.16.81.94] Project...