A Thesis: A CRYPTOGRAPHIC STUDY OF SOME DIGITAL SIGNATURE SCHEMES.

In this thesis, we propose some directed signature schemes. In addition, we have discussed their applications in different situations. In this thesis, we would like to discuss the security aspects during the design process of the proposed directed digital signature schemes. The security of the most digital signature schemes widely use in practice is based on the two difficult problems, viz; the problem of factoring integers (The RSA scheme) and the problem of finding discrete logarithms over finite fields (The ElGamal scheme). The proposed works in this thesis is divided into seven chapters

Mercury of the Waves: Modern Cryptology and U.S. Literature

Mercury of the Waves: Modern Cryptology and U.S. LiteratureHenry VeggianUniversity of Pittsburgh, 2005The doctoral dissertation examines United States literary and institutional history during the period 1900-1973. The study demonstrates how cryptology was detached from its philological residence over three phases (the amateur, institutional, and professional). In the amateur phase, which was regionally specific to the Midwest, the science was characterized by social reformist debate. In the second, institutional phase, the amateur version of cryptology was institutionalized by the United States federal government following WWI to imitate a specific institutional model (that of the French Bureau du Chiffre). During the third, professional phase, the prior two were enhanced during the interwar period by linguists, mechanical engineers, literary modernists, and cryptologists. Running parallel to this narrative is a modern American literary genealogy that, beginning with Henry Adams and extending through Thomas Pynchon, engaged cryptology during that same era. The dissertation locates their discourse within Vichian humanism, and in doing so it first explains how modern literature (and the American novel in particular), its practices, and institutions contributed discursive rhetoric, hermeneutical methods, and institutional models to the emergent 20th century U.S. security state; secondly, it argues that a particular genealogical style that spans the writings of Henry Adams, T.S. Eliot, William Faulkner, Raymond Chandler, and Thomas Pynchon elaborated an diverse rhetorical discourse by which to respond to that assemblage of new institutional entities, and without which that assemblage would be incoherent

Further Information on Miller's 1882 One-Time Pad

New information has been discovered about Frank Miller's 1882 one-time pad. These documents explain Miller's threat model and show that he had a reasonably deep understanding of the problem; they also suggest that his scheme was used more than had been supposed

Vernam, Mauborgne, and Friedman: The One-Time Pad and the Index of Coincidence

The conventional narrative for the invention of the AT and T one-time pad was related by David Kahn. Based on the evidence available in the AT and T patent files and from interviews and correspondence, he concluded that Gilbert Vernam came up with the need for randomness, while Joseph Mauborgne realized the need for a non-repeating key. Examination of other documents suggests a different narrative. It is most likely that Vernam came up with the need for non-repetition; Mauborgne, though, apparently contributed materially to the invention of the two-tape variant. Furthermore, there is reason to suspect that he suggested the need for randomness to Vernam. However, neither Mauborgne, Herbert Yardley, nor anyone at AT and T really understood the security advantages of the true one-time tape. Col. Parker Hitt may have; William Friedman definitely did. Finally, we show that Friedman's attacks on the two-tape variant likely led to his invention of the index of coincidence, arguably the single most important publication in the history of cryptanalysis

The Cryptographic Imagination

Originally published in 1996. In The Cryptographic Imagination, Shawn Rosenheim uses the writings of Edgar Allan Poe to pose a set of questions pertaining to literary genre, cultural modernity, and technology. Rosenheim argues that Poe's cryptographic writing—his essays on cryptography and the short stories that grew out of them—requires that we rethink the relation of poststructural criticism to Poe's texts and, more generally, reconsider the relation of literature to communication. Cryptography serves not only as a template for the language, character, and themes of much of Poe's late fiction (including his creation, the detective story) but also as a "secret history" of literary modernity itself. "Both postwar fiction and literary criticism," the author writes, "are deeply indebted to the rise of cryptography in World War II." Still more surprising, in Rosenheim's view, Poe is not merely a source for such literary instances of cryptography as the codes in Conan Doyle's "The Dancing-Men" or in Jules Verne, but, through his effect on real cryptographers, Poe's writing influenced the outcome of World War II and the development of the Cold War. However unlikely such ideas sound, The Cryptographic Imagination offers compelling evidence that Poe's cryptographic writing clarifies one important avenue by which the twentieth century called itself into being. "The strength of Rosenheim's work extends to a revisionistic understanding of the entirety of literary history (as a repression of cryptography) and then, in a breathtaking shift of register, interlinks Poe's exercises in cryptography with the hyperreality of the CIA, the Cold War, and the Internet. What enables this extensive range of applications is the stipulated tension Rosenheim discerns in the relationship between the forms of the literary imagination and the condition of its mode of production. Cryptography, in this account, names the technology of literary production—the diacritical relationship between decoding and encoding—that the literary imagination dissimulates as hieroglyphics—the hermeneutic relationship between a sign and its content."—Donald E. Pease, Dartmouth Colleg

The Cultural Contradictions of Cryptography

This dissertation examines the origins of political and scientific commitments that currently frame cryptography, the study of secret codes, arguing that these commitments took shape over the course of the twentieth century. Looking back to the nineteenth century, cryptography was rarely practiced systematically, let alone scientifically, nor was it the contentious political subject it has become in the digital age. Beginning with the rise of computational cryptography in the first half of the twentieth century, this history identifies a quarter-century gap beginning in the late 1940s, when cryptography research was classified and tightly controlled in the US. Observing the reemergence of open research in cryptography in the early 1970s, a course of events that was directly opposed by many members of the US intelligence community, a wave of political scandals unrelated to cryptography during the Nixon years also made the secrecy surrounding cryptography appear untenable, weakening the official capacity to enforce this classification. Today, the subject of cryptography remains highly political and adversarial, with many proponents gripped by the conviction that widespread access to strong cryptography is necessary for a free society in the digital age, while opponents contend that strong cryptography in fact presents a danger to society and the rule of law. I argue that cryptography would not have become invested with these deep political commitments if it had not been suppressed in research and the media during the postwar years. The greater the force exerted to dissuade writers and scientists from studying cryptography, the more the subject became wrapped in an aura of civil disobedience and public need. These positive political investments in cryptography have since become widely accepted among many civil libertarians, transparency activists, journalists, and computer scientists who treat cryptography as an essential instrument for maintaining a free and open society in the digital age. Likewise, even as opponents of widespread access to strong cryptography have conceded considerable ground in recent decades, their opposition is grounded in many of the same principles that defined their stance during cryptography’s public reemergence in the 1970s. Studying this critical historical moment reveals not only the origins of cryptography’s current politics, but also the political origins of modern cryptography

Library of Algorithms for Text Ciphering

Tato práce podává přehled historických i moderních metod a postupů využívaných v kryptografii. Popisuje a zhodnocuje šifry, které byly používány od samotných počátků šifrování informací až po šifry používané v dnešní době. Tento přehled by měl čtenáři poskytnout informace, na jejichž základě by byl schopen rozlišovat mezi jednotlivými šiframi, znát jejich výhody a nevýhody a umět zvolit nejvhodnější šifru pro konkrétní účel. Studované šifry jsou implementovány v knihovně CipherLib , která nabízí ukázku použití jednotlivých šifer.This thesis brings an overview of historical and modern methods and approaches used in cryptography. It also describes and assesses ciphers, which have been used since the very beginning of encryption till modern ciphers. Based on information resulting from this overview the reader should be able to distinguish between ciphers, know their advantages and disadvantages, and be able to choose the best cipher for any purpose. Ciphers mentioned in this thesis are implemented in a library called CipherLib , which shows usage of every described cipher.

Classical substitution ciphers and group theory

We explore some connections between classical substitution ciphers, both monoalphabetic and polyalphabetic, and mathematical group theory. We try to do this in a way that is accessible to cryptographers who are not familiar with group theory, and to mathematicians who are not familiar with classical ciphers