The OpenBSD Cryptographic Framework ( OCF ) is a service virtualization layer for the uniform management of cryptographic hardware by an operating system . It is part of the OpenBSD Project, having been included in the operating system since OpenBSD 2.8 (December, 2000). Like other OpenBSD projects such as OpenSSH , it has been ported to other systems based on Berkeley Unix such as FreeBSD and NetBSD , and to Solaris and Linux . One of the Linux ports is supported by Intel for use with its proprietary cryptographic software and hardware to provide hardware-accelerated SSL encryption for the open source Apache HTTP Server .
32-419: Cryptography is computationally intensive and is used in many different contexts. Software implementations often serve as a bottleneck to information flow or increase network latency . Specialist hardware such as cryptographic accelerators can mitigate the bottleneck problem by introducing parallelism . Certain kinds of hardware, hardware random number generators , can also produce randomness more reliably than
64-497: A pseudo-random software algorithm by exploiting the entropy of natural events. Unlike graphics applications such as games and film processing where similar hardware accelerators are in common use and have strong operating system support, the use of hardware in cryptography has had relatively low uptake. By the late 1990s, there was a need for a uniform operating system layer to mediate between cryptographic hardware and application software that used it. The lack of this layer led to
96-462: A telecommunications network . It specifies the latency for a bit of data to travel across the network from one communication endpoint to another. It is typically measured in multiples or fractions of a second. Delay may differ slightly, depending on the location of the specific pair of communicating endpoints. Engineers usually report both the maximum and average delay, and they divide the delay into several parts: A certain minimum level of delay
128-409: A check digit or parity bit can be sent along with the data easily. Parallel transmission is the simultaneous transmission of related signal elements over two or more separate paths. Multiple electrical wires are used which can transmit multiple bits simultaneously, which allows for higher data transfer rates than can be achieved with serial transmission. This method is typically used internally within
160-714: A communications signal means that errors caused by random processes can be detected and corrected. Digital signals can also be sampled instead of continuously monitored. The multiplexing of multiple digital signals is much simpler compared to the multiplexing of analog signals. Because of all these advantages, because of the vast demand to transmit computer data and the ability of digital communications to do so and because recent advances in wideband communication channels and solid-state electronics have allowed engineers to realize these advantages fully, digital communications have grown quickly. The digital revolution has also resulted in many digital telecommunication applications where
192-403: A data source, for example a computer or a keyboard. It may also be an analog signal such as a phone call or a video signal, digitized into a bit-stream for example using pulse-code modulation (PCM) or more advanced source coding (analog-to-digital conversion and data compression) schemes. This source coding and decoding is carried out by codec equipment. In telecommunications, serial transmission
224-617: A form of digital-to-analog conversion . Courses and textbooks in the field of data transmission as well as digital transmission and digital communications have similar content. Digital transmission or data transmission traditionally belongs to telecommunications and electrical engineering . Basic principles of data transmission may also be covered within the computer science or computer engineering topic of data communications, which also includes computer networking applications and communication protocols , for example routing, switching and inter-process communication . Although
256-586: A hardware random number generator, and where possible this facility is used to provide entropy in IPsec. Because OpenSSL uses the OCF, systems with hardware that supports the RSA , DH , or DSA cryptographic protocols will automatically use the hardware without any modification of the software. On 11 December 2010, a former government contractor named Gregory Perry sent an email to OpenBSD project leader Theo de Raadt alleging that
288-622: A passband signal using an analog modulation method such as AM or FM . It may also include analog-over-analog pulse modulated baseband signals such as pulse-width modulation. In a few books within the computer networking tradition, analog transmission also refers to passband transmission of bit-streams using digital modulation methods such as FSK , PSK and ASK . Note that these methods are covered in textbooks named digital transmission or data transmission, for example. The theoretical aspects of data transmission are covered by information theory and coding theory . Courses and textbooks in
320-483: Is a method of conveying voice, data, image, signal or video information using a continuous signal which varies in amplitude, phase, or some other property in proportion to that of a variable. The messages are either represented by a sequence of pulses by means of a line code ( baseband transmission ), or by a limited set of continuously varying waveforms ( passband transmission ), using a digital modulation method. The passband modulation and corresponding demodulation
352-462: Is carried out by modem equipment. Digital communications , including digital transmission and digital reception , is the transfer of either a digitized analog signal or a born-digital bitstream . According to the most common definition, both baseband and passband bit-stream components are considered part of a digital signal ; an alternative definition considers only the baseband signal as digital, and passband transmission of digital data as
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#1732851568044384-420: Is carried out by modem equipment. According to the most common definition of a digital signal, both baseband and passband signals representing bit-streams are considered as digital transmission, while an alternative definition only considers the baseband signal as digital, and passband transmission of digital data as a form of digital-to-analog conversion. Data transmitted may be digital messages originating from
416-476: Is experienced by signals due to the time it takes to transmit a packet serially through a link . This delay is extended by more variable levels of delay due to network congestion . IP network delays can range from a few milliseconds to several hundred milliseconds. This computer networking article is a stub . You can help Misplaced Pages by expanding it . Data transmission Data communication , including data transmission and data reception ,
448-421: Is the sequential transmission of signal elements of a group representing a character or other entity of data . Digital serial transmissions are bits sent over a single wire, frequency or optical path sequentially. Because it requires less signal processing and less chances for error than parallel transmission, the transfer rate of each individual path may be faster. This can be used over longer distances and
480-438: Is the transfer of data , transmitted and received over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires , optical fibers , wireless communication using radio spectrum , storage media and computer buses . The data are represented as an electromagnetic signal , such as an electrical voltage , radiowave , microwave , or infrared signal. Analog transmission
512-480: Is the transfer of a continuously varying analog signal over an analog channel, digital communication is the transfer of discrete messages over a digital or an analog channel. The messages are either represented by a sequence of pulses by means of a line code (baseband transmission), or by a limited set of continuously varying wave forms (passband transmission), using a digital modulation method. The passband modulation and corresponding demodulation (also known as detection)
544-488: Is utilized for transferring many phone calls over the same copper cable or fiber cable by means of pulse-code modulation (PCM) in combination with time-division multiplexing (TDM) (1962). Telephone exchanges have become digital and software controlled, facilitating many value-added services. For example, the first AXE telephone exchange was presented in 1976. Digital communication to the end user using Integrated Services Digital Network (ISDN) services became available in
576-538: The FBI had paid some OpenBSD ex-developers 10 years previously to compromise the security of the system, inserting "a number of backdoors and side channel key leaking mechanisms into the OCF". Theo de Raadt made the email public on 14 December by forwarding it to the openbsd-tech mailing list and suggested an audit of the IPsec codebase. De Raadt's response was skeptical of the report and he invited all developers to independently review
608-492: The Transmission Control Protocol (TCP) involves transmission, TCP and other transport layer protocols are covered in computer networking but not discussed in a textbook or course about data transmission. In most textbooks, the term analog transmission only refers to the transmission of an analog message signal (without digitization) by means of an analog signal, either as a non-modulated baseband signal or as
640-431: The advent of the telephone . However, the first data electromagnetic transmission applications in modern time were electrical telegraphy (1809) and teletypewriters (1906), which are both digital signals . The fundamental theoretical work in data transmission and information theory by Harry Nyquist , Ralph Hartley , Claude Shannon and others during the early 20th century, was done with these applications in mind. In
672-453: The beginning and end of transmission. This method of transmission is used when data are sent intermittently as opposed to in a solid stream. Synchronous transmission synchronizes transmission speeds at both the receiving and sending end of the transmission using clock signals . The clock may be a separate signal or embedded in the data . A continual stream of data is then sent between the two nodes. Due to there being no start and stop bits,
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#1732851568044704-551: The computer, for example, the internal buses, and sometimes externally for such things as printers. Timing skew can be a significant issue in these systems because the wires in parallel data transmission unavoidably have slightly different properties so some bits may arrive before others, which may corrupt the message. This issue tends to worsen with distance making parallel data transmission less reliable for long distances. Some communications channel types include: Asynchronous serial communication uses start and stop bits to signify
736-516: The early 1960s, Paul Baran invented distributed adaptive message block switching for digital communication of voice messages using switches that were low-cost electronics. Donald Davies invented and implemented modern data communication during 1965-7, including packet switching , high-speed routers , communication protocols , hierarchical computer networks and the essence of the end-to-end principle . Baran's work did not include routers with software switches and communication protocols, nor
768-411: The field of data transmission typically deal with the following OSI model protocol layers and topics: It is also common to deal with the cross-layer design of those three layers. Data (mainly but not exclusively informational ) has been sent via non-electronic (e.g. optical , acoustic , mechanical ) means since the advent of communication . Analog signal data has been sent electronically since
800-555: The idea that users, rather than the network itself, would provide the reliability . Both were seminal contributions that influenced the development of computer networks . Data transmission is utilized in computers in computer buses and for communication with peripheral equipment via parallel ports and serial ports such as RS-232 (1969), FireWire (1995) and USB (1996). The principles of data transmission are also utilized in storage media for error detection and correction since 1951. The first practical method to overcome
832-472: The late 1980s. Since the end of the 1990s, broadband access techniques such as ADSL , Cable modems , fiber-to-the-building (FTTB) and fiber-to-the-home (FTTH) have become widespread to small offices and homes. The current tendency is to replace traditional telecommunication services with packet mode communication such as IP telephony and IPTV . Transmitting analog signals digitally allows for greater signal processing capability. The ability to process
864-425: The packet-level encryption protocol, was altered so that packets can be decoded in batches, which improves throughput . One rationale for this is to maximize efficiency of hardware usage—larger batches reduce the bus transmission overhead—but in practice the IPsec developers have found that this strategy improves the efficiency even of software implementations. Many Intel firmware hubs on i386 motherboards provide
896-656: The principles of data transmission are applied. Examples include second-generation (1991) and later cellular telephony , video conferencing , digital TV (1998), digital radio (1999), and telemetry . Data transmission, digital transmission or digital communications is the transfer of data over a point-to-point or point-to-multipoint communication channel. Examples of such channels include copper wires, optical fibers, wireless communication channels, storage media and computer buses. The data are represented as an electromagnetic signal , such as an electrical voltage, radiowave, microwave, or infrared light. While analog transmission
928-486: The problem of receiving data accurately by the receiver using digital code was the Barker code invented by Ronald Hugh Barker in 1952 and published in 1953. Data transmission is utilized in computer networking equipment such as modems (1940), local area network (LAN) adapters (1964), repeaters , repeater hubs , microwave links , wireless network access points (1997), etc. In telephone networks, digital communication
960-410: The production of applications that were hard-coded to work with one or a very small range of cryptographic accelerators. The OpenBSD Project, which has a history of integrating strong, carefully audited cryptography into its operating system's core, produced a framework for the provision of cryptographic hardware acceleration as an operating system service. Application-level support is provided through
992-492: The pseudo-device /dev/crypto , which provides access to the hardware drivers through a standard ioctl interface. This simplifies the writing of applications and removes the need for the application programmer to understand the operational details of the actual hardware that will be used. /dev/crypto was removed in OpenBSD 5.7, having been superseded by the crypto_ suite of syscalls . The OpenBSD implementation of IPsec ,
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1024-484: The relevant code. In the weeks that followed, bugs were fixed but no evidence of backdoors was found. Oracle 's proprietary operating system Solaris (originally developed by Sun ) features an unrelated product called the Solaris Cryptographic Framework, a plug-in system for cryptographic algorithms and hardware. Network latency Network delay is a design and performance characteristic of
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