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POP3S
In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a mail server. POP version 3 (POP3) is the version in common use, and along with IMAP the most common protocols for email retrieval. Purpose The Post Office Protocol provides access via an Internet Protocol (IP) network for a user client application to a mailbox (''maildrop'') maintained on a mail server. The protocol supports download and delete operations for messages. POP3 clients connect, retrieve all messages, store them on the client computer, and finally delete them from the server. This design of POP and its procedures was driven by the need of users having only temporary Internet connections, such as dial-up access, allowing these users to retrieve e-mail when connected, and subsequently to view and manipulate the retrieved messages when offline. POP3 clients also have an option to leave mail on the server after download. By contr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of TCP And UDP Port Numbers
This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for duplex, bidirectional traffic. They usually use port numbers that match the services of the corresponding TCP or UDP implementation, if they exist. The Internet Assigned Numbers Authority (IANA) is responsible for maintaining the official assignments of port numbers for specific uses. However, many unofficial uses of both well-known and registered port numbers occur in practice. Similarly, many of the official assignments refer to protocols that were never or are no longer in common use. This article lists port numbers and their associated protocols that have experienced significant uptake. Table legend Well-known ports The port numbers in the range from 0 to 1023 (0 to 210 − 1) are the ''well-known ports'' or ''system ports''. They are used by system processes that provide wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
STARTTLS
Opportunistic TLS (Transport Layer Security) refers to extensions in plain text communication protocols, which offer a way to upgrade a plain text connection to an encrypted (TLS or SSL) connection instead of using a separate port for encrypted communication. Several protocols use a command named "STARTTLS" for this purpose. It is a form of opportunistic encryption and is primarily intended as a countermeasure to passive monitoring. The STARTTLS command for IMAP and POP3 is defined in , for SMTP in , for XMPP in and for NNTP in . For IRC, the IRCv3 Working Group has defined the STARTTLS extension. FTP uses the command "AUTH TLS" defined in and LDAP defines a protocol extension OID in . HTTP uses upgrade header. Layering TLS is application-neutral; in the words of : :One advantage of TLS is that it is application protocol independent. Higher-level protocols can layer on top of the TLS protocol transparently. The TLS standard, however, does not specify how protocols add sec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Application Layer
An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network. An ''application layer'' abstraction is specified in both the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest-level layer, the detailed definitions and purposes are different. Internet protocol suite In the Internet protocol suite, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client–server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applicatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
POPmail
POPmail was an early e-mail client written at the University of Minnesota. The original version was a Hypercard stack that acted as a Post Office Protocol client. Later versions of POPmail were written as normal Macintosh applications, and a PC version of POPmail was also released. POPmail and Eudora were both instrumental in moving higher education e-mail use away from terminal-based user interfaces and into a client–server GUI metaphor. Searches of USENET news from the late 1980s to the early 1990s illustrate the early adoption of TCP/IP-based mail clients, and the increasing popularity of this approach in the early 1990s. References Classic Mac OS email clients {{network-software-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shared Secret
In cryptography, a shared secret is a piece of data, known only to the parties involved, in a secure communication. This usually refers to the key of a symmetric cryptosystem. The shared secret can be a password, a passphrase, a big number, or an array of randomly chosen bytes. The shared secret is either shared beforehand between the communicating parties, in which case it can also be called a pre-shared key, or it is created at the start of the communication session by using a key-agreement protocol, for instance using public-key cryptography such as Diffie–Hellman or using symmetric-key cryptography Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between ... such as Kerberos. The shared secret can be used for authentication (for instance when logging into a remote system) usi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Replay Attack
A replay attack (also known as a repeat attack or playback attack) is a form of network attack in which valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and re-transmits it, possibly as part of a spoofing attack by IP packet substitution. This is one of the lower-tier versions of a man-in-the-middle attack. Replay attacks are usually passive in nature. Another way of describing such an attack is: "an attack on a security protocol using a replay of messages from a different context into the intended (or original and expected) context, thereby fooling the honest participant(s) into thinking they have successfully completed the protocol run." Example Suppose Alice wants to prove her identity to Bob. Bob requests her password as proof of identity, which Alice dutifully provides (possibly after some transformation like hashing, or even salting, the password); meanwh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptographic Hash Function
A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with fixed size of n bits) that has special properties desirable for cryptography: * the probability of a particular n-bit output result ( hash value) for a random input string ("message") is 2^ (like for any good hash), so the hash value can be used as a representative of the message; * finding an input string that matches a given hash value (a ''pre-image'') is unfeasible, unless the value is selected from a known pre-calculated dictionary ("rainbow table"). The ''resistance'' to such search is quantified as security strength, a cryptographic hash with n bits of hash value is expected to have a ''preimage resistance'' strength of n bits. A ''second preimage'' resistance strength, with the same expectations, refers to a similar problem of finding a second message that matches the given hash value when one message is already known; * finding any pair of different me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kerberized
Kerberos () is a computer-network authentication protocol that works on the basis of ''tickets'' to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. Its designers aimed it primarily at a client–server model, and it provides mutual authentication—both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks. Kerberos builds on symmetric-key cryptography and requires a trusted third party, and optionally may use public-key cryptography during certain phases of authentication.RFC 4556, abstract. Kerberos uses UDP port 88 by default. The protocol was named after the character '' Kerberos'' (or '' Cerberus'') from Greek mythology, the ferocious three-headed guard dog of Hades. History and development Massachusetts Institute of Technology (MIT) developed Kerberos in 1988 to protect network services provided by Project Athena. The p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Project Athena
Project Athena was a joint project of MIT, Digital Equipment Corporation, and IBM to produce a campus-wide distributed computing environment for educational use. It was launched in 1983, and research and development ran until June 30, 1991. , Athena is still in production use at MIT. It works as software (currently a set of Debian packages) that makes a machine a thin client, that will download educational applications from the MIT servers on demand. Project Athena was important in the early history of desktop and distributed computing. It created the X Window System, Kerberos, and Zephyr Notification Service. It influenced the development of thin computing, LDAP, Active Directory, and instant messaging. Description Leaders of the $50 million, five-year project at MIT included Michael Dertouzos, director of the Laboratory for Computer Science; Jerry Wilson, dean of the School of Engineering; and Joel Moses, head of the Electrical Engineering and Computer Science depa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Massachusetts Institute Of Technology
The Massachusetts Institute of Technology (MIT) is a Private university, private Land-grant university, land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the most prestigious and highly ranked academic institutions in the world. Founded in response to the increasing Technological and industrial history of the United States, industrialization of the United States, MIT adopted a European History of European universities, polytechnic university model and stressed laboratory instruction in applied science and engineering. MIT is one of three private land grant universities in the United States, the others being Cornell University and Tuskegee University. The institute has an Campus of the Massachusetts Institute of Technology, urban campus that extends more than a mile (1.6 km) alongside the Charles River, and encompasses a number of major off-campus fa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simple Authentication And Security Layer
Simple Authentication and Security Layer (SASL) is a framework for authentication and data security in Internet protocols. It decouples authentication mechanisms from application protocols, in theory allowing any authentication mechanism supported by SASL to be used in any application protocol that uses SASL. Authentication mechanisms can also support ''proxy authorization'', a facility allowing one user to assume the identity of another. They can also provide a ''data security layer'' offering ''data integrity'' and ''data confidentiality'' services. DIGEST-MD5 provides an example of mechanisms which can provide a data-security layer. Application protocols that support SASL typically also support Transport Layer Security (TLS) to complement the services offered by SASL. John Gardiner Myers wrote the original SASL specification (RFC 2222) in 1997. In 2006, that document was replaced by RFC 4422 authored by Alexey Melnikov and Kurt D. Zeilenga. SASL, as defined by RFC 4422 is an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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