Competition (biology)Competition is an interaction between organisms or species in which both require a resource that is in limited supply (such as food, water, or territory). Competition lowers the fitness of both organisms involved since the presence of one of the organisms always reduces the amount of the resource available to the other. In the study of community ecology, competition within and between members of a species is an important biological interaction.
Camellia (cipher)In cryptography, Camellia is a symmetric key block cipher with a block size of 128 bits and key sizes of 128, 192 and 256 bits. It was jointly developed by Mitsubishi Electric and NTT of Japan. The cipher has been approved for use by the ISO/IEC, the European Union's NESSIE project and the Japanese CRYPTREC project. The cipher has security levels and processing abilities comparable to the Advanced Encryption Standard. The cipher was designed to be suitable for both software and hardware implementations, from low-cost smart cards to high-speed network systems.
Caesar cipherIn cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, would be replaced by , would become , and so on. The method is named after Julius Caesar, who used it in his private correspondence.
Ciphertext-only attackIn cryptography, a ciphertext-only attack (COA) or known ciphertext attack is an attack model for cryptanalysis where the attacker is assumed to have access only to a set of ciphertexts. While the attacker has no channel providing access to the plaintext prior to encryption, in all practical ciphertext-only attacks, the attacker still has some knowledge of the plaintext. For instance, the attacker might know the language in which the plaintext is written or the expected statistical distribution of characters in the plaintext.
Challenge–response authenticationIn computer security, challenge–response authentication is a family of protocols in which one party presents a question ("challenge") and another party must provide a valid answer ("response") to be authenticated. The simplest example of a challenge–response protocol is password authentication, where the challenge is asking for the password and the valid response is the correct password. An adversary who can eavesdrop on a password authentication can then authenticate itself by reusing the intercepted password.
Tying (commerce)Tying (informally, product tying) is the practice of selling one product or service as a mandatory addition to the purchase of a different product or service. In legal terms, a tying sale makes the sale of one good (the tying good) to the de facto customer (or de jure customer) conditional on the purchase of a second distinctive good (the tied good). Tying is often illegal when the products are not naturally related.
Social Security numberIn the United States, a Social Security number (SSN) is a nine-digit number issued to U.S. citizens, permanent residents, and temporary (working) residents under section 205(c)(2) of the Social Security Act, codified as _42. The number is issued to an individual by the Social Security Administration, an independent agency of the United States government. Although the original purpose for the number was for the Social Security Administration to track individuals, the Social Security number has become a de facto national identification number for taxation and other purposes.
Technology adoption life cycleThe technology adoption lifecycle is a sociological model that describes the adoption or acceptance of a new product or innovation, according to the demographic and psychological characteristics of defined adopter groups. The process of adoption over time is typically illustrated as a classical normal distribution or "bell curve". The model indicates that the first group of people to use a new product is called "innovators", followed by "early adopters".
Ecological validityIn the behavioral sciences, ecological validity is often used to refer to the judgment of whether a given study's variables and conclusions (often collected in lab) are sufficiently relevant to its population (e.g. the "real world" context). Psychological studies are usually conducted in laboratories though the goal of these studies is to understand human behavior in the real-world. Ideally, an experiment would have generalizable results that predict behavior outside of the lab, thus having more ecological validity.
September 11 attacksThe September 11 attacks, commonly known as 9/11, were four coordinated Islamist suicide terrorist attacks carried out by al-Qaeda against the United States on Tuesday, September 11, 2001. That morning, 19 terrorists hijacked four commercial airliners scheduled to travel from the New England and Mid-Atlantic regions of the East Coast to California. The hijackers crashed the first two planes into the Twin Towers of the World Trade Center in New York City, two of the world's five-tallest buildings at the time, and aimed the next two flights toward targets in or near Washington, D.
