Computer Security is an information security as applied to computers and networks.Computer Security :

The fields covers all the process and mechanisms by which computers based equipment information and services are protected from unintended or unauthorized access, change or destruction.

Computer security also includes protection from unplanned events and natural disasters.

Network Security comprises the measures a company takes to protect its system and it is a prime concern for every company that uses computers comprised network security means a hacker or competitor may gain access to critical or sensitive data, possibly resulting in data loss, or even complete destruction of the system.Network Security :

On the Other hand, Network Security is typically handled by a network administrator or system administrator who implements the security policy network software and hardware needed to protect a network and resource accessed through the a network from unauthorized access and also ensure that employees have adequate access to the network and resources to work.

Internet Security refers to branch of computer security explicitly related to the internet.Internet Security :

It uses contain software so as to secure computer from the various threats and attacks that originate or come from the internet.

In AES decryption, we use inverse shift rows inverse sub bytes, add round key, inverse mix columns.The difference between the AEC decryption algorithm and the equivalent inverse cipher :

But in equivalent inverse cipher, we interchange inverse shift rows and inverse sub bytes.

Make a comparison between MD5 and SHA :

MD5 SHA 1.MD-5 stands for Message Digest-5. 1.SHA stands for Secure Hash algorithm 2.It uses hash length of 16 bytes. 2.20 bytes 3.Faster procedure 3.Slower 4.Less Secure 4.More secure 5.It returns the 32-bit hexadecimal character 5.40-bit 6.128-bit fingerpint 6.It takes as input the arbitary message size and converts to 160bit fingerprint. 7.MD-5 is one way algorithm 7.SHA is two way algorithm 8.The MD-5 algorithm is slightly cheaper than SHA 8.The SHA algorithm is not cheaper than MD-5 9.SHA-1 take the encrypted value and decrypt the value to get in the original plain text value back. 9.MD-5 cannot take the hashed (or encypted value) and decypt it to get the original plain text value back. 10.This is a standard algorithm which is used to protect credit card data when it is stored within a database 10.To use an MD-5 value you hash the value you want to check to see is encrypted and compare it to the stored hashed values for a match.

The difference Differential Cryptanalysis and cipher Cryptanalysis :

Differential Cryptanalysis Cipher Cryptanalysis 1.Differential Cryptanalysis requires chosen plaintext. 1.known random plaintexts are sufficient. 2.Differential Cryptanalysis is hardder to grasp. 2.easier 3.Differential Cryptanalysis works on differences 3.on linearity 4.Complex procedure 4.Easier procedure 5.Complex attack 5.Infeasible as an attack on DES.

Difference between Conventional and Public :

Conventional Public 1.Private key cryptography(Symmetric). 1.ASymmetric 2.Uses the same cipher and key to encrypt and decrypt. 2.different key 3.stream, block algon 3.single type of algon 4.private key encryption is a comparatively older development 4.recent 5.faster encryption 5.slower 6.secret but distributed 6.private key kept secret but never distributed. 7.eaiser to break 7.hard

Difference between Session key and Master key :

Session key Master key 1.A session key is a temporary encryption key used between two principles. 1.Long -lasting encryption key used between a key distributed center and principal for the purpose of encoding 2.It is used for the duration of a logical connection. 2.Each end system or user there is a unique master key. 3.Example : Frame relay 3.Must be distributed in same fashion.

Difference between private and public key cryptography :

public key cryptography private key cryptography 1.public key cryptography(Asymmetric cryptography) uses two keys- one is called the public key and the other the private key. 1.private key cryptography(symmetric cryptography) uses a single key 2.The public key can be used to decrypt data encrypted by the matching private. 2.Data encrypted using private key can only be decrypted using the matching public key 3.public key cannot be used in the place of the private key 3.private key cannot be used in the place of the public key 4.Less Secure 4.More secure 5.Mix protocol 5.match protocol 6.uses single type of also asymmetric 6.uses stream also or block algo. 7.recent development 7.traditional development 8.public key cannot be used to derive the private key.It's used to communication between two parties 8.This is used for digital signature 9.If the public key is the locking key, then communication. 9.If the public key is the locking key, then the system can be used to verify documents sent by the holder of the private key. 10.If the locking key is made public, this system can be used by anybody to send private communication to the holder of the unlocking key. 10.If the locking key is made public, this system makes it possible to verify that the documents were locked by the owner.

Difference between DES and AES :

DES AES 1.DES stands for Data Encryption Standard. 1.AES stands for Advanced Encryption Standard 2.DES is not secure. 2.AES is secure 3.DES is symmetric encryption algorithm 3.AES is asymmetric encryption algorithm 4.DES use the same key to encrypt and decrypt the message 4.AES use the public key of the receiver to encrypt the message & receiver use its private key to decrypt the message 5.DES is easier to break than AES 5.AES is much harder to break then DES 6.DES need less processing both needs scheme to distribute keys between sender and receiver 6.AES need more processing both needs scheme to distribute keys between sender and receiver.

Difference between Symmetric key and Asymmetric key :

Symmetric key Asymmetric key 1.Symmetric cryptography uses the same secret to encrypt and decrypt data its data. 1.Asymmetric uses both a public and private 2.Symmetric requires that the secret key be known by the party encrypting the data and the party decrypting the data. 2.Asymmetric allows for distributed of your public key to anyone with which they encypt the data they want to send securely and then it can only be decoded by the person having the private key 3.Symmetric ciphers faster then asymmetric 3.Asymmetric ciphers slower then symmetric 4.Symmetric ciphers requires a single key that must be shared by the sender and receiver 4.Asymmetric ciphers solves the key distribution problem by using two keys, one of the which is perfectly fine to share 5.Encryption process is less complicated 5.Encryption process is more complicated 6.Symmetric encryption shemes are less secure then the asymmetric encryption 6.Asymmetric encryption shemes are more secure then the asymmetric encryption.

Difference between Secret Key cryptography and Public key cryptography :

Secret Key cryptography Public key cryptography 1.Symmetric key. 1.Asymmetric key 2.Uses single key. 2.Uses two key 3.Faster 3.public key cryptography is slower than secret key cryptography 4.Secret key must be transmitted either manually or through a communication channel 4.No need to transmit 5.It is simpler then public key cryptography 5.Not simpler

Difference between Block cipher and stream cipher :

Block cipher Stream cipher 1.It proces the input one block of element at a time, producing on output block. 1.Stream cipher in one that a digital data stream one but byte at a time 2.It is used vastly/mostly. 2.It is used less than block cipher 3.Encrypted fixed length blocks of bits 3.It combines plaintext bits with a psedurandom cipher 4.More complex 4.Less complex 5.It cannot operate directly 5.It can operate directly 6.Every block cipher use the same transformation 6.Every block cipher cannot use the same transformation

The essential integriy of a public keys directory :

1. The authority maintains a directory with a entry for each participant.

2. Each participant registers a public key with the directory authority.

3. A participant may people.The existing key with the new one at any time.

4.Periodically, the authority publishers the entire directory on updates to the directory.

5. Participants could also access the directory electronically.

The MAC function is a majority-to-one function, due to the may-t-one nature of the function.MAC.Specify the requirements for message authentication :

using brute force method, how would an opponent attempt to discever a key?.If confidentiality i not employed, the opponent has access to plaintext messages and thir associated MACs.

Suppose k>n; that is suppose that the key size is greater than the MAC size.Then given a known M_{1}and MAC_{1}with

MAC_{1}= c(K,M_{1}), the cryptanalyst can perform.

MAC_{i}= c(k,M;) for all possible key rules k;

A least one key is guaranted to produce a match of MAC_{i}= MAC_{1}.