Cryptography refers to the design of mechanisms based on mathematical algorithms that provide fundamental information security services.

Internet Security measures to protect data during their transmission.

Network Security measures to protect data during their transmission over a collection of interconnected networks.

Interruption is an attack on availability, e.g., destruction of piece of hardware, cutting of a communication line or disabling of file management system.

Interception is an attack on confidentiality, unauthorized party could be a person, a program or a computer.

Fabrication is an attack on integrity. e.g., changing values in data file, altering a program, modifying the contents of messages being transmitted in a network.

Modification is an attack on authenticity. e.g., insertion of spurious message in a network or addition of records to a file.

Security Mechanism is a process that is designed to detect, prevent, or recover from a security attack.

Security Service is processing or communication service that enhances the security of the data processing systems and the information transfers of an organization.

Access Control is the prevention of unauthorized use of a resource.

Data Confidentiality is protection of data from unauthorized disclosure.

Confidentiality is the protection of transmitted data from passive attacks.

Information access threats exploit flaws in computers to inhibit use by legitimate users.

Service threats is intercepting or modifying data on behalf of users who should not have access to that data.

Routing Control enables selection of particular physically secure routes for certain data and allows routing changes, especially when a breach of security is suspected.

Trusted Functionality is perceived to be correst with respect to some criteria.

Notarization use of a trusted third party to asure certain properties of a data exchange.

Pervasive Security Mechanisms are not specific to any particular OST security service or protocol layer.

Notarization use of a trusted third party to assure certain properties of a data exchange.

Symmetric encryption, also referred to as conventional encryption or single-key encryption.

In symmetric key algorithms, the encryption and decryption keys are known both to sender and receiver.

key algorithm for transforming plaintext to ciphertext.

cipher info used in cipher known only to sender/receiver.

decipher (decrypt) converting plaintext to ciphertext.

encipher (encrypt) recovering ciphertext from plaintext.

cryptanalysis is study of encryption principles/methods.

cryptology is the field of both cryptography and cryptanalysis.

cryptography is the study of principles/ methods of deciphering ciphertext without knowing key.

Brute-force attack means that the attacker tries every possible key on a piece of ciphertext until an intelligible translation into plaintext is obtained.

If the plaintext is 1101101 by using key 10111100 with XOR one-time pad cipher, the cipher text is 1001101.

A symmetric-key modern block cipher encrypts an n-bit block of plaintext or decrypts an n-bit block of ciphertext.

The message is divided into n-bit blocks and appropriate padding must be added to the last block if necessary.

The encryption or decryption algorithm uses a k-byte key.

A modern block cipher can be designed to act as only for a substitution cipher.

The symbols to be substituted or transposed are bits instead of characters.

To be resistant to exhaustive-search attack, a modern block cipher needs to be designed as a transposition cipher.

Actual ciphers cannot use full-size keys because the size of the key becomes so large, especially for a substitution cipher.

A keyless (or fixed-key) substitution cipher (or unit) can be thought of as a predefined mapping from the input to the output.

Modern block ciphers normally are keyed substitution ciphers in which the key allows only partial mappings from the possible inputs to the possible outputs.

To provide the required properties, such as diffusion and confusion, a modern block cipher is made of a combination of transposition units (called S-boxes), substitution units (called P-boxes).

A S-box (permutation box) parallels the traditional transposition cipher for characters.

A P-box (substitution box) can be thought of as a miniature substitution cipher.

An S-box can have a different number of inputs and outputs.

The inverse of a component in a cipher makes sense if the component represents a unary operation.

The complement operation is a unary operation that flips each bit in a word.

invertible S-box is meaning the number of input bits should be the same as the number of output bits.

Increasing the number of rounds using more S-boxes may create a better cipher.

A Feistel cipher combine rounds using more Senores ma unit and uses the same unit in the encryption and decryption algorithms.

A noninvetible Functionrynibe aanceled out by using an of operation.

An important connetion can be cancel ciphers is the exolusive-or operation.

(DES) is a symmetric-key block cipher published by the National Instinte of Standards and Technology (NIST).

The eneryption process is made of two permutations (P-boxes), which we call initial and final permutations, and sixteen Feistel rounds.

DES uses 16 rounds. Each round of DES is a Feistel cipher.

The DES function applies a 48-bit key to the rightmost 64 bits to produce a 64. bit output.

DES uses the XOR operation on the expanded right section and the round key.

DES uses 8 S-boxes, each with a 6-bit input and a 4-bit output.

In DES, the round-key generator creates sixteen 48-bit keys out of a 56-bit cipher key.

Completeness effect means that each bit of the ciphertext needs to depend on many bits on the plaintext.

DES uses sixteen rounds of Feistel ciphers. the ciphertext is thoroughly a random function of plaintext and ciphertext.

DES is not a group; this means that we can use double or triple DES to increase the key size.

Triple DES with three keys is used by many applications such as PGP.

The input to the AES encryption and decryption algorithms is a single 128-bit block (16 bytes) of data at time.

The Sub-Bytes operation involves 16 independent byte-to-byte transformations.

The SubBytes and InvSubBytes transformations are inverses of each other.

AES was designed after DES.

The algorithms used in AES are so simple that they can be easily implemented using cheap processors and a minimum amount of memory.

In RSA, encryption needs to generate a pair of koys, namely public key and private key.

Kerberos is a private-key authentication service

X.509 is a private-key directory authentication service

A network eavesdropper should be able to obtain the necessary information to impersonate a user.

Authentication functions developed to support application-level authentication & digital signatures

user should be aware that authentication is taking place

Scalable in network security means capable of supporting large numbers of clients and servers modular, distributed architecture.

Direction control determines the type of internet services that can be accessed, inbound or outbound.

Service control determines the direction in which particular service request may be initiated and allowed to flow through the firewall.

There are 2 common types of firewalls.

A firewall defines a single choke point that keeps unauthorized users out of the protected network

A firewall is a modern platform for several internet functions that are not security related.

The Bastion host serves as a platform for an application level and circuit level gateway.

Each proxy is configured to allow access all specific host systems.

Each proxy is independent of other proxies on the Bastion host.

The Bastion host hardware platform, execues a secure version of its operating system, making it a trusted system.

SET is a communications protocol standard for securing credit card transactions over networks, specifically, the Internet.

A macro is a program that can replicate itself and send copies from computer lised send copies from computer to computer across network connections

Macro viruses are easily spread. A very common method is by network.

Email security is a term for describing different procedures and techniques for protecting email accounts

MIME is a kind of add on or a supplementary protocol which allows non-ASCII data to be sent through SMTP.

S/MIME uses the RSA public key eryptography algorithm along with the DES or RSA encryption algorithm.

IPSec is an Internet Engineering Task Force (IETF) standard suite of protocols between 2 communication points across the IP network that provide data authentication, integrity, and confidentiality.

The Alert Protocol consists of a series of messages exchanged by client and server.

The Handshake Protocol is used to convey SSL-related alerts to the peer entity.

SSL is designed to make use of TCP to provide a reliable end-to-end secure service.

SSL is a single protocol, it consists of one layer of protocols

Secure socket layer (SSL) provides security services between TCP and applications that use TCP.

SSL/TLS provides integrity using symmetric encryption and message confidentiality using a message authentication code.

Secure electronic transaction (SET) is an open encryption and security specification designed to protect credit card transactions on the Internet.

The Authentication Header provides support for data integrity and authentication of IP packets.

cryprosystem consists of, firstly generation of key pair and secondly encryption-decryption algorithms.