Positive systems refer to a class of dynamic systems characterized by non-negativity in their states and outputs. In control theory and systems engineering, a system is considered positive if, given non-negative initial conditions and non-negative inputs, the system's states and outputs will remain non-negative for all time. ### Key Characteristics of Positive Systems: 1. **Non-Negativity**: All states and outputs of the system must stay non-negative whenever initial conditions and inputs are non-negative.

A pulse-swallowing counter is a type of digital counter used in electronics and computer hardware, particularly in applications involving frequency division or time measurement. The term typically refers to a counting mechanism where the counter increments or decrements its count based on specific pulses that are "swallowed" or ignored for control purposes. In more detail, the concept often applies to designs where the frequency of incoming signals (like clock pulses) is reduced or divided by a certain factor.

Viscous damping refers to a type of damping that is proportional to the velocity of an object moving through a fluid or a material. This phenomenon is commonly observed in mechanical systems, particularly in oscillating or vibrating systems, where energy is dissipated as heat due to the resistance of the fluid or medium. In the context of mechanical vibrations, viscous damping can be described using a damping force that is proportional to the velocity (\(v\)) of the object.

The "airport problem" generally refers to a variety of optimization problems related to the operation and management of airports, particularly those involving scheduling, capacity management, and resource allocation. Depending on the context, it can involve several specific issues: 1. **Flight Scheduling**: Determining optimal schedules for arrivals and departures to minimize delays while maximizing the utilization of runways, gates, and other resources.

XXTEA (Corrected Block TEA) is a block cipher designed to provide secure encryption for data. It is an enhancement and refinement of the original TEA (Tiny Encryption Algorithm), which is known for its simplicity and efficiency. XXTEA addresses certain vulnerabilities and limitations in the original TEA design.

"Paradise Lost" is an epic poem written by the English poet John Milton, first published in 1667. The poem is written in blank verse and consists of twelve books. It explores the biblical story of the Fall of Man, depicting the rebellion of Satan and his followers, the creation of humanity, and the subsequent temptation of Adam and Eve that leads to their expulsion from the Garden of Eden.

Classical cryptography refers to traditional methods of encrypting and securing information before the development of modern cryptographic techniques using computers. These classical methods primarily emerged before the 20th century and often involve manual techniques for encoding messages. Here are some of the key features and common techniques associated with classical cryptography: ### Key Features: 1. **Symmetric Key Cryptography**: Most classical cryptographic methods use the same key for both encryption and decryption.

CryptoParty is an event designed to educate individuals about cryptography and digital privacy. These gatherings typically focus on fostering a community-oriented atmosphere where participants can learn about various tools and techniques to secure their online communications and protect their personal data. In a CryptoParty, attendees often learn about topics such as: - Encryption methods and tools (e.g., PGP for securing emails, VPNs for internet privacy) - Best practices for maintaining privacy online - Secure messaging applications (e.g.

"Cypherpunks: Freedom and the Future of the Internet" is a book authored by Julian Assange, the founder of WikiLeaks, along with several prominent figures associated with the cypherpunk movement, including Jacob Appelbaum, Andy Müller-Maguhn, and Jérémie Zimmermann. Published in 2012, the book serves as a manifesto advocating for privacy, digital freedom, and the protection of civil liberties in the face of increasing surveillance and control by governments and corporations.

A Feistel cipher is a type of symmetric key cipher that is widely used in encryption algorithms. It is named after the German-born cryptographer Horst Feistel, who developed the structure in the 1970s. The primary characteristic of a Feistel cipher is its design, which divides the data block into two halves and processes them through multiple rounds of encryption operations.

NIPRNet, or the Non-Secure Internet Protocol Router Network, is the U.S. Department of Defense's unclassified network. It provides a communication infrastructure for the military and other federal agencies to exchange unclassified data over a secure, stable, and reliable network while ensuring a certain level of security. NIPRNet supports a wide range of applications, including email, web browsing, and file sharing, and it allows users to access unclassified information and services.

Online credentials for learning refer to various types of certifications, badges, diplomas, or degrees that individuals can earn through online educational programs. These credentials are often designed to recognize and validate a learner's skills, knowledge, and competencies acquired through online courses, workshops, or training programs. Here are some key aspects of online credentials: 1. **Types of Credentials**: - **Certificates**: Short-term programs that demonstrate mastery of specific skills or knowledge in a particular area.

The PGP word list is a collection of human-readable words used in the Pretty Good Privacy (PGP) encryption system for generating passphrases and keys. It was designed to create memorable and easy-to-communicate phrases that can serve as reliable keys. The original word list contains 2,048 distinct words and is often used to create key fingerprints or passphrases that are more secure than random alphanumeric strings while remaining relatively easy for humans to remember and pronounce.

Proof of knowledge is a concept in cryptography and computer science that pertains to demonstrating that a party (the prover) possesses certain information (usually a secret or private key) without revealing the information itself. It is often associated with zero-knowledge proofs, which are protocols that allow one party to prove to another that they know a value (like a password or cryptographic key) without disclosing the value itself.

Visual cryptography is a cryptographic technique that allows for the encryption of visual information (such as images) in such a way that decryption can be performed visually without requiring complex computations. The concept was introduced by Adi Shamir in 1994. In visual cryptography, an image is divided into multiple shares (or parts) in such a way that each share alone does not reveal any information about the original image.

Server-based signatures refer to a method of digital signing where the cryptographic operations (such as signing) are performed on a dedicated server instead of on a local device or client. This approach is commonly used in various applications, particularly where security, efficiency, and accuracy are required for digital signature processes. ### Key Features of Server-Based Signatures: 1. **Centralized Management**: The signing process is centralized on a server, which allows for more streamlined management of cryptographic keys and signing operations.

Gerard Kleywegt is a mathematician known primarily for his work in the field of computer science and mathematical logic. He has made significant contributions to areas such as formal methods, algorithm design, and data structures.

"Action Philosophers!" is a comic book series created by Fred Van Lente and Ryan Dunlavey. The series, which debuted in 2006, presents a humorous and entertaining look at the lives, ideas, and philosophies of some of history's greatest thinkers. Each issue explores different philosophers, often portraying them in exaggerated, cartoonish styles and placing them in fantastical or anachronistic situations, blending biography and comedy with philosophical concepts.