Siemens SINAUT MD741-1 System Manual page 130

Glossary
DES/3DES
DHCP
DNS
DynDNS provider
130
The symmetrical encryption algorithm (
DES, originally developed by IBM and checked by the NSA, was
determined in 1977 by the American National Bureau of Standards, the
predecessor of today's National Institute of Standards and Technology
(NIST), as the standard for American government institutions.
As this was the first standardized encryption algorithm of all, it quickly
established itself in industry and hence outside the USA.
DES works with a key length of 56 bits, which is no longer considered
secure due to the increase in computing power since 1977.
3DES is a variant of DES. It works with 3-times larger keys, i.e. 168
bits long. It is still considered secure today and is, among other things,
also part of the IPsec standard.
The Dynamic Host Configuration Protocol (DHCP) performs automatic
dynamic assignment of IP addresses and other parameters in a
network. The Dynamic Host Configuration Protocol uses UDP. It was
defined in RFC 2131 and was assigned the UDP ports 67 and 68.
DHCP uses the client – server method, in which the client is assigned
the IP addresses by the server.
Addressing in IP networks is always by means of IP addresses. It is
generally preferable, however, to specify the addressing in the form of
a domain address (i.e. in the form www.abc.xyz.de). If the addressing
is by means of the domain address, then the sender first sends the
domain address to a domain name server (DNS) and gets back the
associated IP address. Only then does the sender address its data to
this IP address.
Also Dynamic DNS provider. Every computer that is connected to the
Internet has an IP address (IP = Internet Protocol). An IP address
consists of up to 4 three-digit numbers, with dots separating each of
the numbers. If the computer is online via the telephone line via
modem, ISDN or ADSL, then the Internet service provider dynamically
assigns it an IP address, i.e. the address changes from session to
session. Even if the computer is online for more than 24 hours without
interruption (e.g. in the case of a flat rate), the IP address is changed
periodically.
For a local computer to be accessible via the Internet, its address must
be known to the external remote station. This is necessary for it to
establish a connection to the local computer. This is not possible,
however, if the address of the local computer constantly changes. It is
possible, however, if the user of the local computer has an account
with a DynamicDNS provider (DNS = Domain Name Server).
Then he can specify there a hostname under which the computer can
be accessed in the future, e.g.: www.xyz.abc.de. Moreover, the
DynamicDNS provider makes available a small program that has to be
installed and executed on the computer concerned. In each Internet
session of the local computer this tool reports to the DynamicDNS
provider which IP address the computer has at the moment. Its domain
name server registers the current hostname - IP address assignment
and reports this to other domain name servers in the Internet.
If now an external computer wants to establish a connection with a
symmetrical encryption)
SINAUT MD741-1
C79000- G8976-C212