CIS 473 Final Question Set 2

Question 1

How does the one-way Hash Functions work ?

Answer 1

• Accepts a variable-size message M as input and produces a fixed-size message digest H(M) as output
• Does not take a secret key as input To authenticate a message, the message digest is sent with themessage in such a way that the message digest is authentic

Question 2

What is the Secure Hash Algorithm ?what and when oraganization develop it ?

Answer 2

SHA was developed by NIST and published as a federal information processing standard (FIPS 180) in 1993 Was revised in 1995 as SHA-1 and published as FIPS 180-1

• The actual standards document is entitled “Secure Hash Standard”
• Based on the hash function MD4 and its design closely models MD4
• Produces 160-bit hash values
• In 2005 NIST announced the intention to phase out approval of SHA-1 and move to a reliance on SHA-2 by 2010

Question 3

How does HMAC happen?

Answer 3

There has been an increased interest in developing a MAC derived from a cryptographic hash code, such as SHA1 Cryptographic hash functions generally execute faster in software than conventional encryption algorithms such as DES Library code for cryptographic hash functions is widely available A hash function such as SHA-1 was not designed for use as a MAC and cannot be used directly for that purpose because it does not rely on a secret key

Question 4

What is the Public Key and How does it get devloped?

Answer 4

is the first truly revolutionary advance in encryption in literally thousandsof years.
Based on mathematical functions rather than on simple operations on bit patterns .
Is asymmetric, involving the use of two separate key

Question 5

What are the misconceptions of Public-Key Encryption Structure ?

Answer 5

There is a feeling that key distribution is trivial when using public-key encryption, compared to the rather cumbersome handshaking involved with key distribution centers for conventional encryption
Public-key encryption is more secure from cryptanalysis than conventional encryption
•Public-key encryption is a general-purpose technique that has made conventional encryption obsolete

Question 6

How does Public and Private key related to each other ?

Answer 6

This is a pair of keys that have been selected so that ifone is used for encryption, the other is used for decryption. The exact transformationsperformed by the encryption algorithm depend on the public orprivate key that is provided as input.

Question 7

How does the symmetric encryption work ?

Answer 7

•For symmetric encryption to work, the two parties to an exchange must share the same key, and that key must be protected from access by others•Frequent key changes are usually desirable to limit the amount of data compromised if an attacker learns the key•Key distribution technique•The means of delivering a key to two parties that wish to exchange data, without allowing others to see the key

Question 8

What is the Kerberos ?

Answer 8

•Key distribution and user authentication service developed at MIT•Provides a centralized authentication server whose function is to authenticate users to servers and servers to users•Relies exclusively on symmetric encryption, making no use of public-key encryption

Question 9

What is Kerberos Version 4 ?

Answer 9

• A basic third-party authentication scheme Authentication Server (AS)
• Users initially negotiate with AS to identify self
• AS provides a non-corruptible authentication credential (ticket granting ticket TGT)•Ticket Granting Server (TGS)
• •Users subsequently request access to other services from TGS on basis of users TGT

Question 10

What is the Key Distribution Using Asymmetric Encryption ?

Answer 10

One of the major roles of public-key encryption is to address the problem of key distribution There are two distinct aspects to the use of public-key encryption in this regard: 1.The distribution of public keys
2. The use of public-key encryption to distribute secret keys
Public-key certificate Consists of a public key plus a user ID of the key owner, with the whole block signed by a trusted third party Typically, the third party is a certificate authority (CA) that is trusted by the user community, such as a government agency or a financial institution. A user can present his or her public key to the authority in a secure manner and obtain a certificate.The user can then publish the certificate Anyone needing this user’s public key can obtain the certificate and verify that it is valid by way of the attached trusted signature

Question 11

What is IEEE 802.1X ?

Answer 11

This is a link layer protocol that enforces authorization beforea port is assigned an IP address. IEEE 802.1X makes use of the ExtensibzleAuthentication Protocol for the authentication process

Question 12

What is Network Access Control (NAC) ? ( 3 answers)

Answer 12

•An umbrella term for managing access to a network
•Authenticates users logging into the network and determines what data they can access and actions they can perform
•Also examines the health of the user’s computer or mobile device

Question 13

What is The Extensible Authentication Protocol (EAP) ?

Answer 13

acts as aframework for network access and authentication protocols. EAP provides a setof protocol messages that can encapsulate various authentication methods to beused between a client and an authentication server.

Question 14

What are the two authentication methods that support EAP ?

Answer 14

• EAP Transport Layer Security

* EAP Tunneled TLS

Question 15

What is EPA Transport Layer Security (EPA TLS) ?

Answer 15

defineshow the TLS protocol can be encapsulated in EAPmessages.EAP-TLS uses the handshake protocol in TLS, not its encryptionmethod.Client and server authenticate each other using digital certificates.Client generates a pre-master secret key by encrypting a random number withthe server’s public key and sends it to the server. Both client and server usethe pre-master to generate the same secret key

Question 16

What is EAP Tunneled TLS ( EAP-TTLS) ?

Answer 16

EAP-TTLS is like EAP-TLS, except onlythe server has a certificate to authenticate itself to the client first. As in EAPTLS,a secure connection (the “tunnel”) is established with secret keys, butthat connection is used to continue the authentication process by authenticatingthe client and possibly the server again using any EAP method orlegacy method such as PAP (Password Authentication Protocol) and CHAP(Challenge-Handshake Authentication Protocol). EAP-TTLS is defined inRFC 5281.

Question 17

What is Secure Socket Layer (SSL) ?What are the example of make use of SSL ?

Answer 17

One of the most widely used security services is the Secure Sockets Layer (SSL) andthe follow-on Internet standard known as Transport Layer Security (TLS).At this level, there are two implementation choices. Forfull generality, SSL (or TLS) could be provided as part of the underlying protocolsuite and therefore be transparent to applications. Alternatively, SSL can be embeddedin specific packages. For example, most browsers come equipped with SSL,and most Web servers have implemented the protocol.

Question 18

what is the relationship between SSL and TCP ?

Answer 18

SSL is designed to make use of TCP to provide a reliable end-to-end secure service.SSL is not a single protocol but rather two layers of protocols

Question 19

In SSL Architecture, what are the two important SSL concepts?

Answer 19

SSL connection and SSL session

Question 20

What is SSL Connection ?

Answer 20

A connection is a transport (in the OSI layering model definition)that provides a suitable type of service. For SSL, such connections arepeer-to-peer relationships. The connections are transient. Every connection isassociated with one session.

Question 21

What is SSL Session ?

Answer 21

An SSL session is an association between a client and a server.Sessions are created by the Handshake Protocol. Sessions define a set of cryptographicsecurity parameters which can be shared among multiple connections.Sessions are used to avoid the expensive negotiation of new securityparameters for each connection.

Question 22

What is Trasport Layer Security (TLS)?

Answer 22

TLS is an IETF standardization initiative whose goal is to produce an Internet standardversion of SSL. TLS is defined as a Proposed Internet Standard in RFC 5246.RFC 5246 is very similar to SSLv3.

Question 23

What are the differences between TLS and RFC 5246 ?

Answer 23

Version number
Message Authentication Code Pseudorandom function
Alert keys
Cipher suites
Client certificate types •Certificate_verify and Finished Messages
• Cryptographic computations Padding

Question 24

What is HTTPS ?

Answer 24

HTTPS (HTTP over SSL) refers to the combination of HTTP and SSL to implementsecure communication between a Web browser and a Web server.The HTTPS capability is built into all modern Web browsers. Its use dependson the Web server supporting HTTPS communication. For example, somesearch engines do not support HTTPS. Google provides HTTPS as an option:https://google.com.

Question 25

What is Secure Shell (SSH) ?

Answer 25

Secure Shell (SSH) is a protocol for secure network communications designedto be relatively simple and inexpensive to implement.

Question 26

What are the characteristics of Transport Layer Protocol?

Answer 26

•Server authentication occurs at the transport layer, based on the server possessing a public/private key pair•A server may have multiple host keys using multiple different asymmetric encryption algorithms•Multiple hosts may share the same host key•The server host key is used during key exchange to authenticate the identity of the host•RFC 4251 dictates two alternative trust models:•The client has a local database that associates each host name with the corresponding public host key•The host name-to-key association is certified by a trusted certification authority (CA); the client only knows the CA root key and can verify the validity of all host keys certified by accepted CAs

Question 27

What methods do a server require for its authentication ?

Answer 27

Public Key, Password, and Hostbased

Question 28

In server authentication method, what is publickey ?

Answer 28

The details of this method depend on the public-key algorithmchosen. In essence, the client sends a message to the server that contains theclient’s public key, with the message signed by the client’s private key. Whenthe server receives this message, it checks whether the supplied key is acceptablefor authentication and, if so, it checks whether the signature is correct.

Question 29

In serverauthentication method, what is password ?

Answer 29

The client sends a message containing a plaintext password,which is protected by encryption by the Transport Layer Protocol.

Question 30

In serverauthentication method, what is hostbased ?

Answer 30

Authentication is performed on the client’s host rather than theclient itself. Thus, a host that supports multiple clients would provide authenticationfor all its clients. This method works by having the client send a signaturecreated with the private key of the client host. Thus, rather than directlyverifying the user’s identity, the SSH server verifies the identity of the clienthost—and then believes the host when it says the user has already authenticatedon the client side.