The act of accessing may mean consuming, entering, or using.
Open source electronic projects - 1 views
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Access control - Wikipedia, the free encyclopedia - 0 views
en.wikipedia.org/...Access_control
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Geographical access control may be enforced by personnel (e.g., border guard, bouncer, ticket checker)
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n alternative of access control in the strict sense (physically controlling access itself) is a system of checking authorized presence, see e.g. Ticket controller (transportation). A variant is exit control, e.g. of a shop (checkout) or a country
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access control refers to the practice of restricting entrance to a property, a building, or a room to authorized persons
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can be achieved by a human (a guard, bouncer, or receptionist), through mechanical means such as locks and keys, or through technological means such as access control systems like the mantrap.
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Historically, this was partially accomplished through keys and locks. When a door is locked, only someone with a key can enter through the door, depending on how the lock is configured. Mechanical locks and keys do not allow restriction of the key holder to specific times or dates. Mechanical locks and keys do not provide records of the key used on any specific door, and the keys can be easily copied or transferred to an unauthorized person. When a mechanical key is lost or the key holder is no longer authorized to use the protected area, the locks must be re-keyed.[citation needed] Electronic access control uses computers to solve the limitations of mechanical locks and keys. A wide range of credentials can be used to replace mechanical keys. The electronic access control system grants access based on the credential presented. When access is granted, the door is unlocked for a predetermined time and the transaction is recorded. When access is refused, the door remains locked and the attempted access is recorded. The system will also monitor the door and alarm if the door is forced open or held open too long after being unlocked
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The above description illustrates a single factor transaction. Credentials can be passed around, thus subverting the access control list. For example, Alice has access rights to the server room, but Bob does not. Alice either gives Bob her credential, or Bob takes it; he now has access to the server room. To prevent this, two-factor authentication can be used. In a two factor transaction, the presented credential and a second factor are needed for access to be granted; another factor can be a PIN, a second credential, operator intervention, or a biometric input
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There are three types (factors) of authenticating information:[2] something the user knows, e.g. a password, pass-phrase or PIN something the user has, such as smart card or a key fob something the user is, such as fingerprint, verified by biometric measurement
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Passwords are a common means of verifying a user's identity before access is given to information systems. In addition, a fourth factor of authentication is now recognized: someone you know, whereby another person who knows you can provide a human element of authentication in situations where systems have been set up to allow for such scenarios
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When a credential is presented to a reader, the reader sends the credential’s information, usually a number, to a control panel, a highly reliable processor. The control panel compares the credential's number to an access control list, grants or denies the presented request, and sends a transaction log to a database. When access is denied based on the access control list, the door remains locked.
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A credential is a physical/tangible object, a piece of knowledge, or a facet of a person's physical being, that enables an individual access to a given physical facility or computer-based information system. Typically, credentials can be something a person knows (such as a number or PIN), something they have (such as an access badge), something they are (such as a biometric feature) or some combination of these items. This is known as multi-factor authentication. The typical credential is an access card or key-fob, and newer software can also turn users' smartphones into access devices.
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An access control point, which can be a door, turnstile, parking gate, elevator, or other physical barrier, where granting access can be electronically controlled. Typically, the access point is a door. An electronic access control door can contain several elements. At its most basic, there is a stand-alone electric lock. The lock is unlocked by an operator with a switch. To automate this, operator intervention is replaced by a reader. The reader could be a keypad where a code is entered, it could be a card reader, or it could be a biometric reader. Readers do not usually make an access decision, but send a card number to an access control panel that verifies the number against an access list
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Generally only entry is controlled, and exit is uncontrolled. In cases where exit is also controlled, a second reader is used on the opposite side of the door. In cases where exit is not controlled, free exit, a device called a request-to-exit (REX) is used. Request-to-exit devices can be a push-button or a motion detector. When the button is pushed, or the motion detector detects motion at the door, the door alarm is temporarily ignored while the door is opened. Exiting a door without having to electrically unlock the door is called mechanical free egress. This is an important safety feature. In cases where the lock must be electrically unlocked on exit, the request-to-exit device also unlocks the doo
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Access control decisions are made by comparing the credential to an access control list. This look-up can be done by a host or server, by an access control panel, or by a reader. The development of access control systems has seen a steady push of the look-up out from a central host to the edge of the system, or the reader. The predominant topology circa 2009 is hub and spoke with a control panel as the hub, and the readers as the spokes. The look-up and control functions are by the control panel. The spokes communicate through a serial connection; usually RS-485. Some manufactures are pushing the decision making to the edge by placing a controller at the door. The controllers are IP enabled, and connect to a host and database using standard networks
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Semi-intelligent readers: have all inputs and outputs necessary to control door hardware (lock, door contact, exit button), but do not make any access decisions. When a user presents a card or enters a PIN, the reader sends information to the main controller, and waits for its response. If the connection to the main controller is interrupted, such readers stop working, or function in a degraded mode. Usually semi-intelligent readers are connected to a control panel via an RS-485 bus.
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Intelligent readers: have all inputs and outputs necessary to control door hardware; they also have memory and processing power necessary to make access decisions independently. Like semi-intelligent readers, they are connected to a control panel via an RS-485 bus. The control panel sends configuration updates, and retrieves events from the readers.
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Systems with IP readers usually do not have traditional control panels, and readers communicate directly to a PC that acts as a host
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Some readers may have additional features such as an LCD and function buttons for data collection purposes (i.e. clock-in/clock-out events for attendance reports), camera/speaker/microphone for intercom, and smart card read/write support
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Smart Contracts - 0 views
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Whether enforced by a government, or otherwise, the contract is the basic building block of a free market economy.
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A smart contract is a set of promises, specified in digital form, including protocols within which the parties perform on the other promises.
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The basic idea of smart contracts is that many kinds of contractual clauses (such as liens, bonding, delineation of property rights, etc.) can be embedded in the hardware and software we deal with, in such a way as to make breach of contract expensive (if desired, sometimes prohibitively so) for the breacher.
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A broad statement of the key idea of smart contracts, then, is to say that contracts should be embedded in the world.
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And where the vending machine, like electronic mail, implements an asynchronous protocol between the vending company and the customer, some smart contracts entail multiple synchronous steps between two or more parties
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Smart contracts reference that property in a dynamic, proactively enforced form, and provide much better observation and verification where proactive measures must fall short.
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The mechanisms of the world should be structured in such a way as to make the contracts (a) robust against naive vandalism, and (b) robust against sophisticated, incentive compatible (rational) breach.
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A third category, (c) sophisticated vandalism (where the vandals can and are willing to sacrifice substantial resources), for example a military attack by third parties, is of a special and difficult kind that doesn't often arise in typical contracting, so that we can place it in a separate category and ignore it here.
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The threat of physical force is an obvious way to embed a contract in the world -- have a judicial system decide what physical steps are to be taken out by an enforcement agency (including arrest, confiscation of property, etc.) in response to a breach of contract
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The need to invoke reactive security can be minimized, but not eliminated, by making contractual arrangements verifiable
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Observation of a contract in progress, in order to detect the first sign of breach and minimize losses, also is a reactive form of security
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From common law, economic theory, and contractual conditions often found in practice, we can distill four basic objectives of contract design
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The disciplines of auditing and investigation roughly correspond with verification of contract performance
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The field of accounting is, roughly speaking, primarily concerned with making contracts an organization is involved in more observable
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This is a generalization of the common law principle of contract privity, which states that third parties, other than the designated arbitrators and intermediaries, should have no say in the enforcement of a contract
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The field of security (especially, for smart contracts, computer and network security), roughly corresponds to the goal of privity.
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Reputation, built-in incentives, "self-enforcing" protocols, and verifiability can all play a strong part in meeting the fourth objective
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Smart contracts often involve trusted third parties, exemplified by an intermediary, who is involved in the performance, and an arbitrator, who is invoked to resolve disputes arising out of performance (or lack thereof)
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In smart contract design we want to get the most out of intermediaries and arbitrators, while minimizing exposure to them
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Legal barriers are the most severe cost of doing business across many jurisdictions. Smart contracts can cut through this Gordian knot of jurisdictions
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Where smart contracts can increase privity, they can decrease vulnerability to capricious jurisdictions
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The field of Electronic Data Interchange (EDI), in which elements of traditional business transactions (invoices, receipts, etc.) are exchanged electronically, sometimes including encryption and digital signature capabilities, can be viewed as a primitive forerunner to smart contracts
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One important task of smart contracts, that has been largely overlooked by traditional EDI, is critical to "the meeting of the minds" that is at the heart of a contract: communicating the semantics of the protocols to the parties involved
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There is ample opportunity in smart contracts for "smart fine print": actions taken by the software hidden from a party to the transaction.
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Thus, via hidden action of the software, the customer is giving away information they might consider valuable or confidential, but the contract has been drafted, and transaction has been designed, in such a way as to hide those important parts of that transaction from the customer.
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To properly communicate transaction semantics, we need good visual metaphors for the elements of the contract. These would hide the details of the protocol without surrendering control over the knowledge and execution of contract terms
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Protocols based on mathematics, called cryptographic protocols, tre the basic building blocks that implement the improved tradeoffs between observability, verifiability, privity, and enforceability in smart contracts
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Where smart contracts can increase observability or verifiability, they can decrease dependence on these obscure local legal codes and enforcement traditions
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Keys are not necessarily tied to identities, and the task of doing such binding turns out to be more difficult than at first glance.
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All public key operation are are done inside an unreadable hardware board on a machine with a very narrow serial-line connection (ie, it carries only a simple single-use protocol with well-verified security) to a dedicated firewall. Such a board is available, for example, from Kryptor, and I believe Viacrypt may also have a PGP-compatable board. This is economical for central sites, but may be less practical for normal users. Besides better security, it has the added advantage that hardware speeds up the public key computations.
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If Mallet's capability is to physically sieze the machine, a weaker form of key protection will suffice. The trick is to hold the keys in volatile memory.
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The data is still vulnerable to a "rubber hose attack" where the owner is coerced into revealing the hidden keys. Protection against rubber hose attacks might require some form of Shamir secret sharing which splits the keys between diverse phgsical sites.
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How does Alice know she has Bob's key? Who, indeed, can be the parties to a smart contract? Can they be defined just by their keys? Do we need biometrics (such as autographs, typed-in passwords, retina scans, etc.)?
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The public key cryptography software package "Pretty Good Privacy" (PGP) uses a model called "the web of trust". Alice chooses introducers whom she trusts to properly identify the map between other people and their public keys. PGP takes it from there, automatically validating any other keys that have been signed by Alice's designated introducers.
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1) Does the key actually belong to whom it appears to belong? In other words, has it been certified with a trusted signature?
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3) Does the key belong to someone you can trust to introduce other introducers? PGP confuses this with criterion (2). It is not clear that any single person has enough judgement to properly undertake task (3), nor has a reasonable institution been proposed that will do so. This is one of the unsolved problems in smart contracts.
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PGP also can be given trust ratings and programmed to compute a weighted score of validity-- for example, two marginally trusted signatures might be considered as credible as one fully trusted signature
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Notaries Public Two different acts are often called "notarization". The first is simply where one swears to the truth of some affidavit before a notary or some other officer entitled to take oaths. This does not require the notary to know who the affiant is. The second act is when someone "acknowledges" before a notary that he has executed a document as ``his own act and deed.'' This second act requires the notary to know the person making the acknowledgment.
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"Identity" is hardly the only thing we might want map to a key. After all, physical keys we use for our house, car, etc. are not necessarily tied to our identity -- we can loan them to trusted friends and relatives, make copies of them, etc. Indeed, in cyberspace we might create "virtual personae" to reflect such multi-person relationships, or in contrast to reflect different parts of our personality that we do not want others to link. Here is a possible classification scheme for virtual personae, pedagogically presented:
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A nym is an identifier that links only a small amount of related information about a person, usually that information deemed by the nym holder to be relevant to a particular organization or community
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With Chaumian credentials, a nym can take advantage of the positive credentials of the holder's other nyms, as provably linked by the is-a-person credential
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A true name is an identifier that links many different kinds of information about an person, such as a full birth name or social security number
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A persona is any perstient pattern of behavior, along with consistently grouped information such as key(s), name(s), network address(es), writing style, and services provided
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A reputable name is a nym or true name that has a good reputation, usually because it carries many positive credentials, has a good credit rating, or is otherwise highly regarded
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Reputable names can be difficult to transfer between parties, because reputation assumes persistence of behavior, but such transfer can sometimes occur (for example, the sale of brand names between companies).
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Blind signatures can be used to construct digital bearer instruments, objects identified by a unique key, and issued, cleared, and redeemed by a clearing agent.
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The clearing agent prevents multiple clearing of particular objects, but can be prevented from linking particular objects one or both of the clearing nyms who transferred that object
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These instruments come in an "online" variety, cleared during every transfer, and thus both verifiable and observable, and an "offline" variety, which can be transfered without being cleared, but is only verifiable when finally cleared, by revealing any the clearing nym of any intermediate holder who transfered the object multiple times (a breach of contract).
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To implement a full transaction of payment for services, we need more than just the digital cash protocol; we need a protocol that guarantees that service will be rendered if payment is made, and vice versa
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A credential is a claim made by one party about another. A positive credential is one the second party would prefer to reveal, such as a degree from a prestigious school, while that party would prefer not to reveal a negative credential such as a bad credit rating.
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A Chaumian credential is a cryptographic protocol for proving one possesses claims made about onself by other nyms, without revealing linkages between those nyms. It's based around the is-a-person credential the true name credential, used to prove the linkage of otherwise unlinkable nyms, and to prevent the transfer of nyms between parties.
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Another form of credential is bearer credential, a digital bearer instrument where the object is a credential. Here the second party in the claim refers to any bearer -- the claim is tied only to the reputable name of issuing organization, not to the nym or true name of the party holding the credential.
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Smart Property We can extend the concept of smart contracts to property. Smart property might be created by embedding smart contracts in physical objects. These embedded protocols would automatically give control of the keys for operating the property to the party who rightfully owns that property, based on the terms of the contract. For example, a car might be rendered inoperable unless the proper challenge-response protocol is completed with its rightful owner, preventing theft. If a loan was taken out to buy that car, and the owner failed to make payments, the smart contract could automatically invoke a lien, which returns control of the car keys to the bank. This "smart lien" might be much cheaper and more effective than a repo man. Also needed is a protocol to provably remove the lien when the loan has been paid off, as well as hardship and operational exceptions. For example, it would be rude to revoke operation of the car while it's doing 75 down the freeway.
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Smart property is software or physical devices with the desired characteristics of ownership embedded into them; for example devices that can be rendered of far less value to parties who lack possesion of a key, as demonstrated via a zero knowledge interactive proof
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One method of implementing smart property is thru operation necessary data (OND): data necessary to the operation of smart property.
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A smart lien is the sharing of a smart property between parties, usually two parties called the owner and the lienholder.
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Many parties, especially new entrants, may lack this reputation capital, and will thus need to be able to share their property with the bank via secure liens
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What about extending the concept of contract to cover agreement to a prearranged set of tort laws? These tort laws would be defined by contracts between private arbitration and enforcement agencies, while customers would have a choice of jurisdictions in this system of free-market "governments".
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If these privately practiced law organizations (PPLs for short) bear ultimate responsibility for the criminal activities of their customers, or need to insure lack of defection or future payments on the part of customers, they may in turn ask for liens against their customers, either in with contractual terms allowing arrest of customers under certain conditions
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Other important areas of liability include consumer liability and property damage (including pollution). There need to mechanisms so that, for example, pollution damage to others' persons or property can be assessed, and liens should exist so that the polluter can be properly charged and the victims paid. Where pollution is quantifiable, as with SO2 emissions, markets can be set up to trade emission rights. The PPLs would have liens in place to monitor their customer's emissions and assess fees where emission rights have been exceeded.
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Stretchable electronics to simplify heart surgery? - 0 views
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Currently this catheter method requires the use of three different devices, which are inserted into the heart in succession: one to map the heart's signals and detect the problem area, a second to control positions of therapeutic actuators and their contact with the epicardium, and a third to burn the tissue away.
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The device is designed to deliver critical, high quality information - such as temperature, mechanical force, and blood flow - to the surgeon in real time.
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O-Send Opto-Electronics (Chongqing) Co., Ltd. - Laser module, Photodetector - 3 views
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company laser supplier detector optics photonics electronics Tibi Jonathan China
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The package I received contained some warranty info, but not even a spec sheet for the Duo R3. I was hoping to have it programmed to make an LED blink today, but I’m at a dead end from the get go here.
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Is Open Source Hardware for People or for Businesses? | Open Electronics - 1 views
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