UMKEHRWALZE D: ENIGMA'S REWIRABLE REFLECTOR - PART III

Umkehrwalze D was a field-rewirable reflector for the German service Enigma machine, introduced primarily on German Air Force cipher networks late in the Second World War. This article discusses the history of the device and the various techniques and machines developed by the British and American signals intelligence agencies to deal with it.     

UMKEHRWALZE D: ENIGMA'S REWIRABLE REFLECTOR - PART I

Umkehrwalze D was a field-rewirable reflector for the German service Enigma machine, introduced primarily on German Air Force cipher networks late in the Second World War. The three parts of this article discuss the history of the device and the various techniques and machines developed by the wartime British and American signals intelligence agencies to deal with it.     

RECOVERING THE WIRING OF ENIGMA'S UMKEHRWALZE A

Umkehrwalze A was the original reflector used in the version of the Enigma machine employed by the German armed services. Its wiring was originally deduced by the Polish cryptanalyst Marian Rejewski in December 1932 or January 1933, but details of the wiring have not previously been published. Sufficient information to recover the wiring analytically is provided in a wartime document by Alan Turing, and other sources have been found to confirm the solution. This paper presents the wiring, along with alternative methods of recovering it from Turing's data.     

History and Modern Cryptanalysis of Enigma's Pluggable Reflector

The development history of Umkehrwalze Dora, Enigma's pluggable reflector, is presented from the first ideas in the mid-1920s to the last development plans and its actual usage in 1945. An Enigma message in three parts, enciphered with Umkehrwalze Dora and intercepted by the British on 11 March 1945, is shown. The successful recovery of the key of this message is described. Modern computer-based cryptanalysis is used to recover the wiring of the unknown “Uncle Dick,” which the British called this field-rewirable reflector. The attack is based on the known ciphertext and plaintext pair from the first part of the intercept. After recovery of the unknown reflector wiring and the daily key, the plaintext of the second part of the message is revealed.     

LITTLEWOOD'S CIPHER PART II: A METHOD OF SOLUTION

The paper enumerates the allowable combinations of decipherable boolean functions of certain types, namely functions of a given number of message and key bits. Such an enumeration is based upon decipherable functions property of being one-to-one. Formulas for finding the number of decipherable boolean functions are also given.     

三维动画技术与三维虚拟技术的研究

目前三维图形技术主要包括两大类：三维动画技术和三维虚拟技术。该文的目的是研究两种技术的开发原理,并通过对两种技术的对比,进一步说明了三维虚拟仿真技术在实时性、交互性方面的优势。该文首先介绍了三维动画技术的应用原理、开发步骤,重点阐述了三维虚拟技术中的实时显示技术和交互技术,给出了虚拟仿真应用的开发方法及基于两种技术的应用实例,并对两种技术在实时性、交互性、时间性和三维建模效果等方面作了比较,最后展望三维虚拟技术的发展方向。     

CustomCut: On‐demand Extraction of Customized 3D Parts with 2D Sketches

Several applications in shape modeling and exploration require identification and extraction of a 3D shape part matching a 2D sketch. We present CustomCut, an on‐demand part extraction algorithm. Given a sketched query, CustomCut automatically retrieves partially matching shapes from a database, identifies the region optimally matching the query in each shape, and extracts this region to produce a customized part that can be used in various modeling applications. In contrast to earlier work on sketch‐based retrieval of predefined parts, our approach can extract arbitrary parts from input shapes and does not rely on a prior segmentation into semantic components. The method is based on a novel data structure for fast retrieval of partial matches: the randomized compound k‐NN graph built on multi‐view shape projections. We also employ a coarse‐to‐fine strategy to progressively refine part boundaries down to the level of individual faces. Experimental results indicate that our approach provides an intuitive and easy means to extract customized parts from a shape database, and significantly expands the design space for the user. We demonstrate several applications of our method to shape design and exploration.     

CageR: Cage‐Based Reverse Engineering of Animated 3D Shapes

We present CageR: A novel framework for converting animated 3D shape sequences into compact and stable cage‐based representations. Given a raw animated sequence with one‐to‐one point correspondences together with an initial cage embedding, our algorithm automatically generates smoothly varying cage embeddings which faithfully reconstruct the enclosed object deformation. Our technique is fast, automatic, oblivious to the cage coordinate system, provides controllable error and exploits a GPU implementation. At the core of our method, we introduce a new algebraic algorithm based on maximum volume sub‐matrices (maxvol) to speed up and stabilize the deformation inversion. We also present a new spectral regularization algorithm that can apply arbitrary regularization terms on selected subparts of the inversion spectrum. This step allows to enforce a highly localized cage regularization, guaranteeing its smooth variation along the sequence. We demonstrate the speed, accuracy and robustness of our framework on various synthetic and acquired data sets. The benefits of our approach are illustrated in applications such as animation compression and post‐editing.