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Plaintext, Encryption, Ciphertext: a History of Cryptography and Its Influence on Contemporary Society

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TOC PLAINTEXT, ENCRYPTION, CIPHERTEXT: A HISTORY OF CRYPTOGRAPHY AND ITS INFLUENCE ON CONTEMPORARY SOCIETY QUINN DUPONT PHD DISSERTATION UNIVERSITY OF TORONTO, FACULTY OF INFORMATION CHAPTER 1 “REPRESENTATION” – SUBMISSION TO SIGCIS 2015 DRAFT (PLEASE DO NOT DISTRIBUTE) 1 TOC TABLE OF CONTENTS 1.! Introduction i.! Philological complexity ii.! What do we know of cryptography? iii.! Rewriting three schemata iv.! Chapter summaries Part One: Plaintext 2.! Representation i.! Alberti’s notation ii.! Mimesis and media iii.! Ancient theories of mimesis i.! Plato’s theory of mimesis ii.! Aristotle’s theory of mimesis iv.! Late medieval and renaissance web of resemblances v.! Conventia in memory techniques from Lull to Alberti’s cipher wheel vi.! Aemulatio, analogy, and sympathy in Trithemius’ magical cryptography 3.! Media and notation i.! Francis Bacon’s artifcial languages (1605-1623) i.! Francis Bacon’s bi-literal cipher ii.! Te development of notational schemes (1605-1686) iii.! Notational discourse networks i.! Identity and the alphabet ii.! A theory of notation 4.! Codes and codeworks i.! Agrippa (a book of the dead) i.! Forensic description of Agrippa ii.! Te compiled binary iii.! Te cryptographic algorithm 1.! Encryption efect 2.! Te “self-destruct” mechanism ii.! Bitcoin iii.! Executable software Part Two: Encryption 5.! Media of perception 6.! Communication and transmission 7.! Translation and Transcription 2 TOC Part Tree: Ciphertext 8.! Otherness and order, revealed 9.! Silence 10.! Epilogue i.! Politics: Homogeneity and visibility ii.! Rise of mnenotechnologies iii.! Ubiquitous cryptography 3 PART 1 – PLAINTEXT CHAPTER 2 – REPRESENTATION PLAINTEXT In his seminal work on cryptography De componendis cifris,1 Leon Battista Alberti (1404-1472) diverts from his task of exploring and inventing cryptography systems to recall a time strolling through a garden with his friend Dati. In the garden Alberti and Dati got to discussing Alberti’s desire to have his cryptog- raphy manual printed using the emerging “system of movable type” developed by “the German inventor [Gutenberg].”2 This convivial introduction to the invention of the polyalphabetic cipher might seem mis- placed—after all, the polyalphabetic cipher was a significant invention in its own right,3 and seemingly unrelated to print and typography. In fact, in Alberti’s entire corpus this is the only mention of the inven- tion of printing.4 Yet Alberti notes that it was such discussions with his friend that “brought us to similar appreciations… [of] strange characters with unusual meanings… called ciphers.”5 Rather than being a confused or mistaken association, this leap from movable type to ciphers is intended to signal deeper con- nections between writing, printing, and cryptography—the way that plaintext is articulated within a notational discourse network that ruptures ancient and medieval notions of representation and resem- blances by ushering in ideals of combinatory modularity and indexicality. Movable type was invented in Alberti’s lifetime and proved influential for him; Carpo calls Alberti the first “typographical architect.”6 For Alberti, the invention of movable type highlighted reproducible, mod- ular, indexical, and combinatory logics—logics inherent in the alphabet in the first place, but fully operationalized and made readily apparent in print. Alberti would put these logics to work in both his ar- chitectural and cryptographic theory. Alberti was familiar with the idea of reproducing identical copies from woodcuts, a pre-Gutenberg technique now called xylography.7 Xylography produced whole “images,” typically an etched image or vis- ual depiction. Xylography can even be used to reproduce a complete page (a “single-leaf” woodcut), including textual elements. Entire books—texts and images together—could be printed using xylographic processes, but this “block book” process was rare and may have even originated after Gutenberg’s inven- tion, as a quick and cheap alternative to movable type. In either configuration, image or text, producing duplicates from woodcuts was, once the original etch- ing is complete, a comparatively high-speed production technique. However, as Kittler notes, movable type presses were not designed to compete with the speed of xylography, instead they competed with the elegance of manuscript pages.8 And more to the point, printing from woodcuts, while possible, was rela- tively uncommon because each successive “edition” introduced the chance of error; this is a critical worry for technical works. The chance of copyist error was so high that authors typically wrote textual descrip- tions of what are fundamentally visual phenomena, such as architectural plans and forms (an “ekphrastic” 1 De componendis cifris was written in 1466 and remained in manuscript form during Alberti’s life. A modern Eng- lish translation by Kim William is available in Williams, March, and Wassell, The Mathematical Works of Leon Battista Alberti. References will be made to this edition, using modern page numbers and section divisions. The Latin version has been published in Meister, Die Geheimschrift Im Dienste Der Päpstlichen Kurie von Ihren Anfängen Bis Zum Ende Des XVI Jahrhunderts. 2 Alberti, “De Componendis Cifris,” 170 (ii). It seems Alberti was also aware of the work by Arnold Pannartz and Konrad Sweinheim, who introduced Roman typefaces; see March’s commentary, ibid., 189. March explains away this passage as an attempt to have his manuscript printed with the support of his patron or perhaps Pope Paul II. 3 Kahn, The Codebreakers. 4 Carpo, Architecture in the Age of Printing, 119. 5 Alberti, “De Componendis Cifris,” 170. 6 Carpo, The Alphabet and the Algorithm. 7 Carpo, Architecture in the Age of Printing. 8 Kittler, “The Perspective of Print.” 1 PART 1 – PLAINTEXT CHAPTER 2 – REPRESENTATION mode of expression), rather than employ pictorial techniques so susceptible to copying errors.9 Alberti was so worried of error that in his architectural works he stressed that copyists should write out numbers in longhand rather than using numeric symbols, even addressing the copyist directly in the work in several cases.10 Avoiding the introduction of errors was one of the principle advantages of alphabetic and typographic expression for the reproduction of technical works. Copyists could be counted on to (somewhat) reliably replicate the correct order of a determinate set of icons (the alphabet)—although even here, text rather than numeric symbols was the safer bet. Either way, copyists could not be counted on to replicate intricate pictorial content.11 To draw a technical image is to invite critical mistakes in the production of new man- uscripts or etchings. Carpo summarizes the reticence of those engaged in engineering and scientific communication: “The pretypographical architect knew that for… long-distance transmission, images were not a trustworthy medium. And he practiced his craft within these limitations.”12 Furthermore, the quattrocento era of Alberti is characterized by the expansion of economic, diplomatic, and scientific com- merce. Long-distance transmission of materials of many types became vitally important alongside the demands for secret diplomatic communication. To satisfy this need, Alberti argued, cryptography is needed—which has to be secret, capable of long distance transmission, and above all efficient (Alberti calls it “commodious” [scribetur commodius]).13 Error propagation is a real concern for cryptography. Alberti’s polyalphabetic encryption “mixes” multi- ple alphabets with plaintext that results in a kind of “diffuse” ciphertext. For any one letter of plaintext the corresponding ciphertext may be several letters, or mixed about in unnatural ways. The redundancy of natural languages permits transmission on noisy channels since redundant information accommodates er- rors. For cryptography, this redundancy is, ideally, deeply compromised. So-called “diffusion” and “confusion” techniques are basic methods available to cryptography, as they frustrate cryptanalytic tech- niques by “hiding” plaintext more deeply within a combinatory space.14 The result of highly diffuse ciphertext (what is typically understood as “good” cryptography) is that its transmission becomes very “brittle.” Even a small copying or transcription error may render much or all of the resulting ciphertext impossible to decrypt. Very careful transcription, or error-correction codes (as we use today) are a practi- cal necessity for cryptography.15 By the fifteenth century the introduction of type begun displacing the process of creating manuscripts by hand, which originally required the inscription of letters in situ (at the time of production). On a printed page letters pre-exist as units of type before the creation of words in which they occur. Roy Harris suggests that the “mechanical regularity of print confers upon each alphabetical symbol an independence and a constant visual identity which no earlier form of writing quite achieves.”16 In Alberti’s architectural work the letter became a metaphor for modularity, suggesting that the built form can be assembled just like a word created from its constitutive letters. The invention of the printing press transformed letters from icons in the imagination to manipulatable materials. Individual letters, in the form of literal pieces of metal, were quite obviously distinct from one another, yet each letter produced near-identical impressions with each use. One consequence of this 9 Carpo, Architecture in the Age of Printing,
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