104-529: In cryptography, PKCS ( Public Key Cryptography Standards ) are a group of public-key cryptography standards devised and published by RSA Security LLC, starting in the early 1990s. The company published the standards to promote the use of the cryptography techniques for which they had patents , such as the RSA algorithm , the Schnorr signature algorithm and several others. Though not industry standards (because
208-427: A relational database to categorize cultural works and their images. Relational databases and metadata work to document and describe the complex relationships amongst cultural objects and multi-faceted works of art, as well as between objects and places, people, and artistic movements. Relational database structures are also beneficial within collecting institutions and museums because they allow for archivists to make
312-469: A symmetric key , which is then used by symmetric-key cryptography to transmit data using the now-shared symmetric key for a symmetric key encryption algorithm. PGP , SSH , and the SSL/TLS family of schemes use this procedure; they are thus called hybrid cryptosystems . The initial asymmetric cryptography-based key exchange to share a server-generated symmetric key from the server to client has
416-639: A " brute-force key search attack ". However, such an attack is impractical if the amount of computation needed to succeed – termed the "work factor" by Claude Shannon – is out of reach of all potential attackers. In many cases, the work factor can be increased by simply choosing a longer key. But other algorithms may inherently have much lower work factors, making resistance to a brute-force attack (e.g., from longer keys) irrelevant. Some special and specific algorithms have been developed to aid in attacking some public key encryption algorithms; both RSA and ElGamal encryption have known attacks that are much faster than
520-411: A " man-in-the-middle attack " is possible, making any subordinate certificate wholly insecure. Most of the available public-key encryption software does not conceal metadata in the message header, which might include the identities of the sender and recipient, the sending date, subject field, and the software they use etc. Rather, only the body of the message is concealed and can only be decrypted with
624-454: A "data element" registry, its purpose is to support describing and registering metadata content independently of any particular application, lending the descriptions to being discovered and reused by humans or computers in developing new applications, databases, or for analysis of data collected in accordance with the registered metadata content. This standard has become the general basis for other kinds of metadata registries, reusing and extending
728-581: A British cryptographer at the UK Government Communications Headquarters (GCHQ), conceived of the possibility of "non-secret encryption", (now called public key cryptography), but could see no way to implement it. In 1973, his colleague Clifford Cocks implemented what has become known as the RSA encryption algorithm , giving a practical method of "non-secret encryption", and in 1974 another GCHQ mathematician and cryptographer, Malcolm J. Williamson , developed what
832-772: A class-attribute-value triple. The first 2 elements of the triple (class, attribute) are pieces of some structural metadata having a defined semantic. The third element is a value, preferably from some controlled vocabulary, some reference (master) data. The combination of the metadata and master data elements results in a statement which is a metacontent statement i.e. "metacontent = metadata + master data". All of these elements can be thought of as "vocabulary". Both metadata and master data are vocabularies that can be assembled into metacontent statements. There are many sources of these vocabularies, both meta and master data: UML, EDIFACT, XSD, Dewey/UDC/LoC, SKOS, ISO-25964, Pantone, Linnaean Binomial Nomenclature, etc. Using controlled vocabularies for
936-417: A clear distinction between cultural objects and their images; an unclear distinction could lead to confusing and inaccurate searches. An object's materiality, function, and purpose, as well as the size (e.g., measurements, such as height, width, weight), storage requirements (e.g., climate-controlled environment), and focus of the museum and collection, influence the descriptive depth of the data attributed to
1040-407: A document or communication. Further applications built on this foundation include: digital cash , password-authenticated key agreement , time-stamping services and non-repudiation protocols. Because asymmetric key algorithms are nearly always much more computationally intensive than symmetric ones, it is common to use a public/private asymmetric key-exchange algorithm to encrypt and exchange
1144-414: A key length, the chief security risk is that the private key of a pair becomes known. All security of messages, authentication, etc., will then be lost. Additionally, with the advent of quantum computing , many asymmetric key algorithms are considered vulnerable to attacks, and new quantum-resistant schemes are being developed to overcome the problem. All public key schemes are in theory susceptible to
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#17327975290341248-485: A key topic in efforts toward international standardization . Standards for metadata in digital libraries include Dublin Core , METS , MODS , DDI , DOI , URN , PREMIS schema, EML , and OAI-PMH . Leading libraries in the world give hints on their metadata standards strategies. The use and creation of metadata in library and information science also include scientific publications: Metadata for scientific publications
1352-408: A library might hold in its collection. Until the 1980s, many library catalogs used 3x5 inch cards in file drawers to display a book's title, author, subject matter, and an abbreviated alpha-numeric string ( call number ) which indicated the physical location of the book within the library's shelves. The Dewey Decimal System employed by libraries for the classification of library materials by subject
1456-691: A long list of "self-signed identity certificates" from PKI providers – these are used to check the bona fides of the certificate authority and then, in a second step, the certificates of potential communicators. An attacker who could subvert one of those certificate authorities into issuing a certificate for a bogus public key could then mount a "man-in-the-middle" attack as easily as if the certificate scheme were not used at all. An attacker who penetrates an authority's servers and obtains its store of certificates and keys (public and private) would be able to spoof, masquerade, decrypt, and forge transactions without limit, assuming that they were able to place themselves in
1560-604: A major advantage over your opponent. Only at the end of the evolution from Berners-Lee designing an open internet architecture for CERN , its adaptation and adoption for the Arpanet ... did public key cryptography realise its full potential. — Ralph Benjamin These discoveries were not publicly acknowledged for 27 years, until the research was declassified by the British government in 1997. In 1976, an asymmetric key cryptosystem
1664-550: A man-in-the-middle attack relatively straightforward. Capturing the public key would only require searching for the key as it gets sent through the ISP's communications hardware; in properly implemented asymmetric key schemes, this is not a significant risk. In some advanced man-in-the-middle attacks, one side of the communication will see the original data while the other will receive a malicious variant. Asymmetric man-in-the-middle attacks can prevent users from realizing their connection
1768-597: A prior shared secret. Merkle's "public key-agreement technique" became known as Merkle's Puzzles , and was invented in 1974 and only published in 1978. This makes asymmetric encryption a rather new field in cryptography although cryptography itself dates back more than 2,000 years. In 1977, a generalization of Cocks's scheme was independently invented by Ron Rivest , Adi Shamir and Leonard Adleman , all then at MIT . The latter authors published their work in 1978 in Martin Gardner 's Scientific American column, and
1872-511: A problem with alternative approaches: Here's a new language we want you to learn, and now you need to output these additional files on your server. It's a hassle. (Microformats) lower the barrier to entry. Most common types of computer files can embed metadata, including documents, (e.g. Microsoft Office files, OpenDocument files, PDF ) images, (e.g. JPEG , PNG ) Video files, (e.g. AVI , MP4 ) and audio files. (e.g. WAV , MP3 ) Metadata may be added to files by users, but some metadata
1976-493: A public key encryption system is for encrypting communication to provide confidentiality – a message that a sender encrypts using the recipient's public key, which can be decrypted only by the recipient's paired private key. Another application in public key cryptography is the digital signature . Digital signature schemes can be used for sender authentication . Non-repudiation systems use digital signatures to ensure that one party cannot successfully dispute its authorship of
2080-484: A purpose-built program running on a server computer – vouches for the identities assigned to specific private keys by producing a digital certificate. Public key digital certificates are typically valid for several years at a time, so the associated private keys must be held securely over that time. When a private key used for certificate creation higher in the PKI server hierarchy is compromised, or accidentally disclosed, then
2184-427: A resource. Statistical data repositories have their own requirements for metadata in order to describe not only the source and quality of the data but also what statistical processes were used to create the data, which is of particular importance to the statistical community in order to both validate and improve the process of statistical data production. An additional type of metadata beginning to be more developed
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#17327975290342288-486: A trusted courier. This key, which both parties must then keep absolutely secret, could then be used to exchange encrypted messages. A number of significant practical difficulties arise with this approach to distributing keys . In his 1874 book The Principles of Science , William Stanley Jevons wrote: Can the reader say what two numbers multiplied together will produce the number 8616460799 ? I think it unlikely that anyone but myself will ever know. Here he described
2392-485: A wired route inside the sender's own building. In summation, public keys are easier to alter when the communications hardware used by a sender is controlled by an attacker. One approach to prevent such attacks involves the use of a public key infrastructure (PKI); a set of roles, policies, and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public-key encryption. However, this has potential weaknesses. For example,
2496-461: A year, regardless of whether or not they [ever] were persons of interest to the agency. Geospatial metadata relates to Geographic Information Systems (GIS) files, maps, images, and other data that is location-based. Metadata is used in GIS to document the characteristics and attributes of geographic data, such as database files and data that is developed within a GIS. It includes details like who developed
2600-676: Is accessibility metadata . Accessibility metadata is not a new concept to libraries; however, advances in universal design have raised its profile. Projects like Cloud4All and GPII identified the lack of common terminologies and models to describe the needs and preferences of users and information that fits those needs as a major gap in providing universal access solutions. Those types of information are accessibility metadata. Schema.org has incorporated several accessibility properties based on IMS Global Access for All Information Model Data Element Specification. The Wiki page WebSchemas/Accessibility lists several properties and their values. While
2704-842: Is " data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: Metadata is not strictly bound to one of these categories, as it can describe a piece of data in many other ways. Metadata has various purposes. It can help users find relevant information and discover resources . It can also help organize electronic resources, provide digital identification, and archive and preserve resources. Metadata allows users to access resources by "allowing resources to be found by relevant criteria, identifying resources, bringing similar resources together, distinguishing dissimilar resources, and giving location information". Metadata of telecommunication activities including Internet traffic
2808-438: Is an early example of metadata usage. The early paper catalog had information regarding whichever item was described on said card: title, author, subject, and a number as to where to find said item. Beginning in the 1980s and 1990s, many libraries replaced these paper file cards with computer databases. These computer databases make it much easier and faster for users to do keyword searches. Another form of older metadata collection
2912-491: Is being accomplished in the national and international standards communities, especially ANSI (American National Standards Institute) and ISO (International Organization for Standardization) to reach a consensus on standardizing metadata and registries. The core metadata registry standard is ISO / IEC 11179 Metadata Registries (MDR), the framework for the standard is described in ISO/IEC 11179-1:2004. A new edition of Part 1
3016-486: Is clear that he uses the term in the ISO 11179 "traditional" sense, which is "structural metadata" i.e. "data about the containers of data"; rather than the alternative sense "content about individual instances of data content" or metacontent, the type of data usually found in library catalogs. Since then the fields of information management, information science, information technology, librarianship, and GIS have widely adopted
3120-470: Is completely discrete from other elements and classified according to one dimension only. An example of a linear metadata schema is the Dublin Core schema, which is one-dimensional. Metadata schemata are often 2 dimensional, or planar, where each element is completely discrete from other elements but classified according to 2 orthogonal dimensions. The degree to which the data or metadata is structured
3224-413: Is compromised. This remains so even when one user's data is known to be compromised because the data appears fine to the other user. This can lead to confusing disagreements between users such as "it must be on your end!" when neither user is at fault. Hence, man-in-the-middle attacks are only fully preventable when the communications infrastructure is physically controlled by one or both parties; such as via
PKCS - Misplaced Pages Continue
3328-401: Is genuine by verifying the signature using the public key. As long as the software publisher keeps the private key secret, even if a forger can distribute malicious updates to computers, they cannot convince the computers that any malicious updates are genuine. For example, a journalist can publish the public key of an encryption key pair on a web site so that sources can send secret messages to
3432-560: Is in its final stage for publication in 2015 or early 2016. It has been revised to align with the current edition of Part 3, ISO/IEC 11179-3:2013 which extends the MDR to support the registration of Concept Systems. (see ISO/IEC 11179 ). This standard specifies a schema for recording both the meaning and technical structure of the data for unambiguous usage by humans and computers. ISO/IEC 11179 standard refers to metadata as information objects about data, or "data about data". In ISO/IEC 11179 Part-3,
3536-454: Is more work to be done. Metadata (metacontent) or, more correctly, the vocabularies used to assemble metadata (metacontent) statements, is typically structured according to a standardized concept using a well-defined metadata scheme, including metadata standards and metadata models . Tools such as controlled vocabularies , taxonomies , thesauri , data dictionaries , and metadata registries can be used to apply further standardization to
3640-608: Is most commonly used in museum contexts for object identification and resource recovery purposes. Metadata is developed and applied within collecting institutions and museums in order to: Many museums and cultural heritage centers recognize that given the diversity of artworks and cultural objects, no single model or standard suffices to describe and catalog cultural works. For example, a sculpted Indigenous artifact could be classified as an artwork, an archaeological artifact, or an Indigenous heritage item. The early stages of standardization in archiving, description and cataloging within
3744-454: Is never trivial and very rapidly becomes unmanageable as the number of participants increases, or when secure channels are not available, or when, (as is sensible cryptographic practice), keys are frequently changed. In particular, if messages are meant to be secure from other users, a separate key is required for each possible pair of users. By contrast, in a public-key cryptosystem, the public keys can be disseminated widely and openly, and only
3848-533: Is no intelligence or "inferencing" occurring, just the illusion thereof. Metadata schemata can be hierarchical in nature where relationships exist between metadata elements and elements are nested so that parent-child relationships exist between the elements. An example of a hierarchical metadata schema is the IEEE LOM schema, in which metadata elements may belong to a parent metadata element. Metadata schemata can also be one-dimensional, or linear, where each element
3952-636: Is not only on creation and capture, but moreover on maintenance costs. As soon as the metadata structures become outdated, so too is the access to the referred data. Hence granularity must take into account the effort to create the metadata as well as the effort to maintain it. In all cases where the metadata schemata exceed the planar depiction, some type of hypermapping is required to enable display and view of metadata according to chosen aspect and to serve special views. Hypermapping frequently applies to layering of geographical and geological information overlays. International standards apply to metadata. Much work
4056-462: Is now known as Diffie–Hellman key exchange . The scheme was also passed to the US's National Security Agency . Both organisations had a military focus and only limited computing power was available in any case; the potential of public key cryptography remained unrealised by either organization: I judged it most important for military use ... if you can share your key rapidly and electronically, you have
4160-494: Is often automatically added to files by authoring applications or by devices used to produce the files, without user intervention. While metadata in files are useful for finding them, they can be a privacy hazard when the files are shared. Using metadata removal tools to clean files before sharing them can mitigate this risk. Metadata may be written into a digital photo file that will identify who owns it, copyright and contact information, what brand or model of camera created
4264-403: Is often created by journal publishers and citation databases such as PubMed and Web of Science . The data contained within manuscripts or accompanying them as supplementary material is less often subject to metadata creation, though they may be submitted to e.g. biomedical databases after publication. The original authors and database curators then become responsible for metadata creation, with
PKCS - Misplaced Pages Continue
4368-412: Is referred to as "granularity" . "Granularity" refers to how much detail is provided. Metadata with a high granularity allows for deeper, more detailed, and more structured information and enables a greater level of technical manipulation. A lower level of granularity means that metadata can be created for considerably lower costs but will not provide as detailed information. The major impact of granularity
4472-774: Is saved as persistent repository and describe business objects in various enterprise systems and applications. Structural metadata commonality is also important to support data virtualization. Standardization and harmonization work has brought advantages to industry efforts to build metadata systems in the statistical community. Several metadata guidelines and standards such as the European Statistics Code of Practice and ISO 17369:2013 ( Statistical Data and Metadata Exchange or SDMX) provide key principles for how businesses, government bodies, and other entities should manage statistical data and metadata. Entities such as Eurostat , European System of Central Banks , and
4576-523: Is stored in the integrated library management system, ILMS , using the MARC metadata standard. The purpose is to direct patrons to the physical or electronic location of items or areas they seek as well as to provide a description of the item/s in question. More recent and specialized instances of library metadata include the establishment of digital libraries including e-print repositories and digital image libraries. While often based on library principles,
4680-485: Is the bibliographic classification, the subject, the Dewey Decimal class number . There is always an implied statement in any "classification" of some object. To classify an object as, for example, Dewey class number 514 (Topology) (i.e. books having the number 514 on their spine) the implied statement is: "<book><subject heading><514>". This is a subject-predicate-object triple, or more importantly,
4784-778: Is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key . Key pairs are generated with cryptographic algorithms based on mathematical problems termed one-way functions . Security of public-key cryptography depends on keeping the private key secret; the public key can be openly distributed without compromising security. There are many kinds of public-key cryptosystems, with different security goals, including digital signature , Diffie-Hellman key exchange , public-key key encapsulation , and public-key encryption . Public key algorithms are fundamental security primitives in modern cryptosystems , including applications and protocols that offer assurance of
4888-484: Is the use by the US Census Bureau of what is known as the "Long Form". The Long Form asks questions that are used to create demographic data to find patterns of distribution. Libraries employ metadata in library catalogues , most commonly as part of an Integrated Library Management System . Metadata is obtained by cataloging resources such as books, periodicals, DVDs, web pages or digital images. This data
4992-567: Is usually expressed as a set of keywords in a natural language. According to Ralph Kimball , metadata can be divided into three categories: technical metadata (or internal metadata), business metadata (or external metadata), and process metadata . NISO distinguishes three types of metadata: descriptive, structural, and administrative. Descriptive metadata is typically used for discovery and identification, as information to search and locate an object, such as title, authors, subjects, keywords, and publisher. Structural metadata describes how
5096-420: Is very widely collected by various national governmental organizations. This data is used for the purposes of traffic analysis and can be used for mass surveillance . Metadata was traditionally used in the card catalogs of libraries until the 1980s when libraries converted their catalog data to digital databases . In the 2000s, as data and information were increasingly stored digitally, this digital data
5200-420: The U.S. Environmental Protection Agency have implemented these and other such standards and guidelines with the goal of improving "efficiency when managing statistical business processes". Metadata has been used in various ways as a means of cataloging items in libraries in both digital and analog formats. Such data helps classify, aggregate, identify, and locate a particular book, DVD, magazine, or any object
5304-419: The contents and context of data or data files increases its usefulness. For example, a web page may include metadata specifying what software language the page is written in (e.g., HTML), what tools were used to create it, what subjects the page is about, and where to find more information about the subject. This metadata can automatically improve the reader's experience and make it easier for users to find
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#17327975290345408-499: The CCO, are integrated within a Museum's Collections Management System (CMS), a database through which museums are able to manage their collections, acquisitions, loans and conservation. Scholars and professionals in the field note that the "quickly evolving landscape of standards and technologies" creates challenges for cultural documentarians, specifically non-technically trained professionals. Most collecting institutions and museums use
5512-563: The Library of Congress Controlled Vocabularies are reputable within the museum community and are recommended by CCO standards. Museums are encouraged to use controlled vocabularies that are contextual and relevant to their collections and enhance the functionality of their digital information systems. Controlled Vocabularies are beneficial within databases because they provide a high level of consistency, improving resource retrieval. Metadata structures, including controlled vocabularies, reflect
5616-421: The PKI system (software, hardware, and management) is trust-able by all involved. A " web of trust " decentralizes authentication by using individual endorsements of links between a user and the public key belonging to that user. PGP uses this approach, in addition to lookup in the domain name system (DNS). The DKIM system for digitally signing emails also uses this approach. The most obvious application of
5720-517: The advantage of not requiring that a symmetric key be pre-shared manually, such as on printed paper or discs transported by a courier, while providing the higher data throughput of symmetric key cryptography over asymmetric key cryptography for the remainder of the shared connection. As with all security-related systems, there are various potential weaknesses in public-key cryptography. Aside from poor choice of an asymmetric key algorithm (there are few that are widely regarded as satisfactory) or too short
5824-411: The algorithm came to be known as RSA , from their initials. RSA uses exponentiation modulo a product of two very large primes , to encrypt and decrypt, performing both public key encryption and public key digital signatures. Its security is connected to the extreme difficulty of factoring large integers , a problem for which there is no known efficient general technique. A description of the algorithm
5928-812: The assistance of automated processes. Comprehensive metadata for all experimental data is the foundation of the FAIR Guiding Principles , or the standards for ensuring research data are findable , accessible , interoperable , and reusable . Such metadata can then be utilized, complemented, and made accessible in useful ways. OpenAlex is a free online index of over 200 million scientific documents that integrates and provides metadata such as sources, citations , author information , scientific fields , and research topics. Its API and open source website can be used for metascience, scientometrics , and novel tools that query this semantic web of papers . Another project under development, Scholia , uses
6032-413: The attacker using the correct public keys for the different communication segments so as to avoid suspicion. A communication is said to be insecure where data is transmitted in a manner that allows for interception (also called " sniffing "). These terms refer to reading the sender's private data in its entirety. A communication is particularly unsafe when interceptions can not be prevented or monitored by
6136-563: The author is, when the document was written, and a short summary of the document. Metadata within web pages can also contain descriptions of page content, as well as key words linked to the content. These links are often called "Metatags", which were used as the primary factor in determining order for a web search until the late 1990s. The reliance on metatags in web searches was decreased in the late 1990s because of "keyword stuffing", whereby metatags were being largely misused to trick search engines into thinking some websites had more relevance in
6240-434: The available metadata to a third party. The concept is based around an open repository containing separately encrypted metadata blocks and encrypted messages. Only the intended recipient is able to decrypt the metadata block, and having done so they can identify and download their messages and decrypt them. Such a messaging system is at present in an experimental phase and not yet deployed. Scaling this method would reveal to
6344-447: The brute-force approach. None of these are sufficiently improved to be actually practical, however. Major weaknesses have been found for several formerly promising asymmetric key algorithms. The "knapsack packing" algorithm was found to be insecure after the development of a new attack. As with all cryptographic functions, public-key implementations may be vulnerable to side-channel attacks that exploit information leakage to simplify
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#17327975290346448-441: The certificate authority issuing the certificate must be trusted by all participating parties to have properly checked the identity of the key-holder, to have ensured the correctness of the public key when it issues a certificate, to be secure from computer piracy, and to have made arrangements with all participants to check all their certificates before protected communications can begin. Web browsers , for instance, are supplied with
6552-495: The communication stream. Despite its theoretical and potential problems, Public key infrastructure is widely used. Examples include TLS and its predecessor SSL , which are commonly used to provide security for web browser transactions (for example, most websites utilize TLS for HTTPS ). Aside from the resistance to attack of a particular key pair, the security of the certification hierarchy must be considered when deploying public key systems. Some certificate authority – usually
6656-827: The company retained control over them), some of the standards have begun to move into the " standards track " processes of relevant standards organizations in recent years, such as the IETF and the PKIX working group. This container format can contain multiple embedded objects, such as multiple certificates. Usually protected/encrypted with a password. Usable as a format for the Java KeyStore and to establish client authentication certificates in Mozilla Firefox. Usable by Apache Tomcat . Public-key cryptography Public-key cryptography , or asymmetric cryptography ,
6760-574: The components of an object are organized. An example of structural metadata would be how pages are ordered to form chapters of a book. Finally, administrative metadata gives information to help manage the source. Administrative metadata refers to the technical information, such as file type, or when and how the file was created. Two sub-types of administrative metadata are rights management metadata and preservation metadata. Rights management metadata explains intellectual property rights , while preservation metadata contains information to preserve and save
6864-428: The components of metacontent statements, whether for indexing or finding, is endorsed by ISO 25964 : "If both the indexer and the searcher are guided to choose the same term for the same concept, then relevant documents will be retrieved." This is particularly relevant when considering search engines of the internet, such as Google. The process indexes pages and then matches text strings using its complex algorithm; there
6968-415: The confidentiality and authenticity of electronic communications and data storage. They underpin numerous Internet standards, such as Transport Layer Security (TLS) , SSH , S/MIME , and PGP . Compared to symmetric cryptography , public-key cryptography can be too slow for many purposes, so these protocols often combine symmetric cryptography with public-key cryptography in hybrid cryptosystems . Before
7072-741: The content is desirable. This is particularly useful in video applications such as Automatic Number Plate Recognition and Vehicle Recognition Identification software, wherein license plate data is saved and used to create reports and alerts. There are 2 sources in which video metadata is derived: (1) operational gathered metadata, that is information about the content produced, such as the type of equipment, software, date, and location; (2) human-authored metadata, to improve search engine visibility, discoverability, audience engagement, and providing advertising opportunities to video publishers. Avid's MetaSync and Adobe's Bridge are examples of professional video editing software with access to metadata. Information on
7176-436: The corresponding private keys need be kept secret. The two best-known types of public key cryptography are digital signature and public-key encryption : For example, a software publisher can create a signature key pair and include the public key in software installed on computers. Later, the publisher can distribute an update to the software signed using the private key, and any computer receiving an update can confirm it
7280-464: The data, when it was collected, how it was processed, and what formats it's available in, and then delivers the context for the data to be used effectively. Metadata can be created either by automated information processing or by manual work. Elementary metadata captured by computers can include information about when an object was created, who created it, when it was last updated, file size, and file extension. In this context an object refers to any of
7384-413: The data; it is used to summarize basic information about data that can make tracking and working with specific data easier. Some examples include: For example, a digital image may include metadata that describes the size of the image, its color depth, resolution, when it was created, the shutter speed, and other data. A text document's metadata may contain information about how long the document is, who
7488-467: The efforts to describe and standardize the varied accessibility needs of information seekers are beginning to become more robust, their adoption into established metadata schemas has not been as developed. For example, while Dublin Core (DC)'s "audience" and MARC 21's "reading level" could be used to identify resources suitable for users with dyslexia and DC's "format" could be used to identify resources available in braille, audio, or large print formats, there
7592-506: The file, along with exposure information (shutter speed, f-stop, etc.) and descriptive information, such as keywords about the photo, making the file or image searchable on a computer and/or the Internet. Some metadata is created by the camera such as, color space, color channels, exposure time, and aperture (EXIF), while some is input by the photographer and/or software after downloading to a computer. Most digital cameras write metadata about
7696-446: The focus on non-librarian use, especially in providing metadata, means they do not follow traditional or common cataloging approaches. Given the custom nature of included materials, metadata fields are often specially created e.g. taxonomic classification fields, location fields, keywords, or copyright statement. Standard file information such as file size and format are usually automatically included. Library operation has for decades been
7800-425: The following: A metadata engine collects, stores and analyzes information about data and metadata in use within a domain. Data virtualization emerged in the 2000s as the new software technology to complete the virtualization "stack" in the enterprise. Metadata is used in data virtualization servers which are enterprise infrastructure components, alongside database and application servers. Metadata in these servers
7904-638: The information objects are data about Data Elements, Value Domains, and other reusable semantic and representational information objects that describe the meaning and technical details of a data item. This standard also prescribes the details for a metadata registry, and for registering and administering the information objects within a Metadata Registry. ISO/IEC 11179 Part 3 also has provisions for describing compound structures that are derivations of other data elements, for example through calculations, collections of one or more data elements, or other forms of derived data. While this standard describes itself originally as
8008-417: The level of contribution and the responsibilities. Moreover, various metadata about scientific outputs can be created or complemented – for instance, scite.ai attempts to track and link citations of papers as 'Supporting', 'Mentioning' or 'Contrasting' the study. Other examples include developments of alternative metrics – which, beyond providing help for assessment and findability, also aggregate many of
8112-434: The location the photo was taken from may also be included. Photographic Metadata Standards are governed by organizations that develop the following standards. They include, but are not limited to: Metadata is particularly useful in video, where information about its contents (such as transcripts of conversations and text descriptions of its scenes) is not directly understandable by a computer, but where an efficient search of
8216-438: The metadata application is manifold, covering a large variety of fields, there are specialized and well-accepted models to specify types of metadata. Bretherton & Singley (1994) distinguish between two distinct classes: structural/control metadata and guide metadata. Structural metadata describes the structure of database objects such as tables, columns, keys and indexes. Guide metadata helps humans find specific items and
8320-463: The metadata of scientific publications for various visualizations and aggregation features such as providing a simple user interface summarizing literature about a specific feature of the SARS-CoV-2 virus using Wikidata 's "main subject" property. In research labor, transparent metadata about authors' contributions to works have been proposed – e.g. the role played in the production of the paper,
8424-524: The metadata. Structural metadata commonality is also of paramount importance in data model development and in database design . Metadata (metacontent) syntax refers to the rules created to structure the fields or elements of metadata (metacontent). A single metadata scheme may be expressed in a number of different markup or programming languages, each of which requires a different syntax. For example, Dublin Core may be expressed in plain text, HTML , XML , and RDF . A common example of (guide) metacontent
8528-414: The mid-1970s, all cipher systems used symmetric key algorithms , in which the same cryptographic key is used with the underlying algorithm by both the sender and the recipient, who must both keep it secret. Of necessity, the key in every such system had to be exchanged between the communicating parties in some secure way prior to any use of the system – for instance, via a secure channel . This requirement
8632-720: The model number, shutter speed, etc., and some enable you to edit it; this functionality has been available on most Nikon DSLRs since the Nikon D3 , on most new Canon cameras since the Canon EOS 7D , and on most Pentax DSLRs since the Pentax K-3. Metadata can be used to make organizing in post-production easier with the use of key-wording. Filters can be used to analyze a specific set of photographs and create selections on criteria like rating or capture time. On devices with geolocation capabilities like GPS (smartphones in particular),
8736-683: The museum community began in the late 1990s with the development of standards such as Categories for the Description of Works of Art (CDWA), Spectrum, CIDOC Conceptual Reference Model (CRM), Cataloging Cultural Objects (CCO) and the CDWA Lite XML schema. These standards use HTML and XML markup languages for machine processing, publication and implementation. The Anglo-American Cataloguing Rules (AACR), originally developed for characterizing books, have also been applied to cultural objects, works of art and architecture. Standards, such as
8840-461: The news organization in ciphertext. Only the journalist who knows the corresponding private key can decrypt the ciphertexts to obtain the sources' messages—an eavesdropper reading email on its way to the journalist cannot decrypt the ciphertexts. However, public-key encryption does not conceal metadata like what computer a source used to send a message, when they sent it, or how long it is. Public-key encryption on its own also does not tell
8944-427: The numbers themselves can be perceived as the data. But if given the context that this database is a log of a book collection, those 13-digit numbers may now be identified as ISBNs – information that refers to the book, but is not itself the information within the book. The term "metadata" was coined in 1968 by Philip Bagley, in his book "Extension of Programming Language Concepts" where it
9048-635: The object by cultural documentarians. The established institutional cataloging practices, goals, and expertise of cultural documentarians and database structure also influence the information ascribed to cultural objects and the ways in which cultural objects are categorized. Additionally, museums often employ standardized commercial collection management software that prescribes and limits the ways in which archivists can describe artworks and cultural objects. As well, collecting institutions and museums use Controlled Vocabularies to describe cultural objects and artworks in their collections. Getty Vocabularies and
9152-411: The private key of the intended recipient. This means that a third party could construct quite a detailed model of participants in a communication network, along with the subjects being discussed, even if the message body itself is hidden. However, there has been a recent demonstration of messaging with encrypted headers, which obscures the identities of the sender and recipient, and significantly reduces
9256-588: The public discussions about a scientific paper on social media such as Reddit , citations on Misplaced Pages , and reports about the study in the news media – and a call for showing whether or not the original findings are confirmed or could get reproduced . Metadata in a museum context is the information that trained cultural documentation specialists, such as archivists , librarians , museum registrars and curators , create to index, structure, describe, identify, or otherwise specify works of art, architecture, cultural objects and their images. Descriptive metadata
9360-516: The purposes of discovery. The original set of 15 classic metadata terms, known as the Dublin Core Metadata Element Set are endorsed in the following standards documents: The W3C Data Catalog Vocabulary (DCAT) is an RDF vocabulary that supplements Dublin Core with classes for Dataset, Data Service, Catalog, and Catalog Record. DCAT also uses elements from FOAF, PROV-O, and OWL-Time. DCAT provides an RDF model to support
9464-576: The recipient anything about who sent a message —it just conceals the content of the message. One important issue is confidence/proof that a particular public key is authentic, i.e. that it is correct and belongs to the person or entity claimed, and has not been tampered with or replaced by some (perhaps malicious) third party. There are several possible approaches, including: A public key infrastructure (PKI), in which one or more third parties – known as certificate authorities – certify ownership of key pairs. TLS relies upon this. This implies that
9568-452: The registration and administration portion of the standard. The Geospatial community has a tradition of specialized geospatial metadata standards, particularly building on traditions of map- and image-libraries and catalogs. Formal metadata is usually essential for geospatial data, as common text-processing approaches are not applicable. The Dublin Core metadata terms are a set of vocabulary terms that can be used to describe resources for
9672-467: The relationship of one-way functions to cryptography, and went on to discuss specifically the factorization problem used to create a trapdoor function . In July 1996, mathematician Solomon W. Golomb said: "Jevons anticipated a key feature of the RSA Algorithm for public key cryptography, although he certainly did not invent the concept of public key cryptography." In 1970, James H. Ellis ,
9776-547: The search for a secret key. These are often independent of the algorithm being used. Research is underway to both discover, and to protect against, new attacks. Another potential security vulnerability in using asymmetric keys is the possibility of a "man-in-the-middle" attack , in which the communication of public keys is intercepted by a third party (the "man in the middle") and then modified to provide different public keys instead. Encrypted messages and responses must, in all instances, be intercepted, decrypted, and re-encrypted by
9880-493: The search than they really did. Metadata can be stored and managed in a database , often called a metadata registry or metadata repository . However, without context and a point of reference, it might be impossible to identify metadata just by looking at it. For example: by itself, a database containing several numbers, all 13 digits long could be the results of calculations or a list of numbers to plug into an equation – without any other context,
9984-514: The sender. A man-in-the-middle attack can be difficult to implement due to the complexities of modern security protocols. However, the task becomes simpler when a sender is using insecure media such as public networks, the Internet , or wireless communication. In these cases an attacker can compromise the communications infrastructure rather than the data itself. A hypothetical malicious staff member at an Internet service provider (ISP) might find
10088-474: The term. In these fields, the word metadata is defined as "data about data". While this is the generally accepted definition, various disciplines have adopted their own more specific explanations and uses of the term. Slate reported in 2013 that the United States government's interpretation of "metadata" could be broad, and might include message content such as the subject lines of emails. While
10192-407: The third party only the inbox server being used by the recipient and the timestamp of sending and receiving. The server could be shared by thousands of users, making social network modelling much more challenging. During the early history of cryptography , two parties would rely upon a key that they would exchange by means of a secure, but non-cryptographic, method such as a face-to-face meeting, or
10296-601: The times, origins and destinations of phone calls, electronic messages, instant messages, and other modes of telecommunication, as opposed to message content, is another form of metadata. Bulk collection of this call detail record metadata by intelligence agencies has proven controversial after disclosures by Edward Snowden of the fact that certain Intelligence agencies such as the NSA had been (and perhaps still are) keeping online metadata on millions of internet users for up to
10400-450: The typical structure of a catalog that contains records, each describing a dataset or service. Although not a standard, Microformat (also mentioned in the section metadata on the internet below) is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata. Microformat follows XHTML and HTML standards but is not a standard in itself. One advocate of microformats, Tantek Çelik , characterized
10504-439: The web page online. A CD may include metadata providing information about the musicians, singers, and songwriters whose work appears on the disc. In many countries, government organizations routinely store metadata about emails, telephone calls, web pages, video traffic, IP connections, and cell phone locations. Metadata means "data about data". Metadata is defined as the data providing information about one or more aspects of
10608-628: Was described using metadata standards . The first description of "meta data" for computer systems is purportedly noted by MIT's Center for International Studies experts David Griffel and Stuart McIntosh in 1967: "In summary then, we have statements in an object language about subject descriptions of data and token codes for the data. We also have statements in a meta language describing the data relationships and transformations, and ought/is relations between norm and data." Unique metadata standards exist for different disciplines (e.g., museum collections, digital audio files , websites , etc.). Describing
10712-517: Was published by Whitfield Diffie and Martin Hellman who, influenced by Ralph Merkle 's work on public key distribution, disclosed a method of public key agreement. This method of key exchange, which uses exponentiation in a finite field , came to be known as Diffie–Hellman key exchange . This was the first published practical method for establishing a shared secret-key over an authenticated (but not confidential) communications channel without using
10816-840: Was published in the Mathematical Games column in the August 1977 issue of Scientific American . Since the 1970s, a large number and variety of encryption, digital signature, key agreement, and other techniques have been developed, including the Rabin cryptosystem , ElGamal encryption , DSA and ECC . Examples of well-regarded asymmetric key techniques for varied purposes include: Examples of asymmetric key algorithms not yet widely adopted include: Examples of notable – yet insecure – asymmetric key algorithms include: Examples of protocols using asymmetric key algorithms include: Metadata Metadata (or metainformation )
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