What are the two types of cryptography systems used in encryption today quizlet?

IP Security (IPSec) is an open-source protocol framework for security development within the TCP/IP family of protocol standards.

-It is used to secure communications across IP-based networks such as LANs, WANs, and the Internet. The protocol is designed to protect data integrity, user confidentiality, and authenticity at the IP packet level. IPSec is the cryptographic authentication and encryption product of the IETF's IP Protocol Security Working Group. It is often described as the security system from IP version 6, the future version of the TCP/IP protocol, retrofitted for use with IP version 4 (the current version).

-IPSec is defined in Request for Comments (RFC) 1825, 1826, and 1827, and is widely used to create virtual private networks (VPNs). IPSec itself is an open framework.

-IPSec includes the IP Security protocol itself, which specifies the information to be added to an IP packet as well as how to encrypt packet data; and the Internet Key Exchange, which uses an asymmetric-based key exchange and negotiates the security associations.

IPSec operates in two modes: transport and tunnel.
-In transport mode, only the IP data is encrypted, not the IP headers. This allows intermediate nodes to read the source and destination addresses.
-In tunnel mode, the entire IP packet is encrypted and then placed into the content portion of another IP packet.
This requires other systems at the beginning and end of the tunnel to act as proxies and to send and receive the encrypted packets. These systems then transmit the decrypted packets to their true destinations.

-IPSec uses several different cryptosystems:
• Diffie-Hellman key exchange for deriving key material between peers on a public network
• Public-key cryptography for signing the Diffie-Hellman exchanges to guarantee the identity of the two parties
• Bulk encryption algorithms, such as DES, for encrypting the data
• Digital certificates signed by a certificate authority to act as digital ID cards

Within IPSec, IP layer security is achieved by means of an application header protocol or an encapsulating security payload protocol.
-The application header (AH) protocol provides system-to-system authentication and data integrity verification, but does not provide secrecy for the content of a network communication.
-The encapsulating security payload (ESP) protocol provides secrecy for the contents of network communications as well as system-to-system authentication and data integrity verification.

-When two networked systems form an association that uses encryption and authentication keys, algorithms, and key lifetimes, they can implement either the AH or the ESP protocol, but not both.

-The AH protocol is designed to provide data integrity and IP packet authentication. Although AH does not provide confidentiality protection, IP packets are protected from replay attacks and address spoofing as well as other types of cyberattacks against open net-works.

-Packet format of the IPSec authentication header protocol:
As shown in this diagram, the security parameters index (SPI) references the session key and algorithm used to protect the data being transported. Sequence numbers allow packets to arrive out of sequence for reassembly. The integrity check value (ICV) of the authentication data serves as a check sum to verify that the packet itself is unaltered. Whether used in IPv4 or IPv6, authentication secures the entire packet, excluding mutable fields in the new IP header. In tunnel mode, however, the entire inner IP packet is secured by the authentication header protocol.

-The ESP protocol provides confidentiality services for IP packets across insecure networks. ESP can also provide the authentication services of AH.

-ESP in tunnel mode can be used to establish a virtual private network, assuring encryption and authentication between networks communicating via the Internet. In tunnel mode, the entire IP packet is encrypted with the attached ESP header. A new IP header is attached to the encrypted payload, providing the required routing information.

-An ESP header is inserted into the IP packet prior to the TCP header, and an ESP trailer is placed after the IPv4 packet. If authentication is desired, an ESP authentication data field is appended after the ESP trailer. The complete transport segment, in addition to the ESP trailer, is encrypted. In an IPv6 transmission, the ESP header is placed after the hop-by-hop and routing headers. Encryption under IPv6 covers the transport segment and the ESP trailer. Authentication in both IPv4 and IPv6 covers the ciphertext data plus the ESP header.

-IPSec ESP-compliant systems must support the implementation of the DES algorithm using the CBC (cipher block chaining) mode, which incorporates the following encryption algorithms: Triple DES, IDEA, RC5, CAST, and Blowfish.

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