Draw Model For Network Security Computer Science Essay

Draw Model For Network Security Computer Science send awayvasSENDER Sender transfer message to other troupe through some sort of internet. RECEIVER Receiver receives message send by vector through some sort of internet. Trusted third party trusted third party is needed o secure the message transmits from one party to another. Third party distributes secret in material bodyation to both the parties. Third party actually provides authenticity of message transmission.Opponent An opponent can be a human or a virus that can harm the transmitted message going through some sort of internet.Secure message It is a message to which a secret place is applied which is not in readable by opponent.Secret information Secret information is a refer applied to message.Ques2Why is polyalphabetic substitution superior to monoalphatic substitution.Ans Polyalphabetic ciphers use multiple substitution alphabetic.A monoalphabetic substitution replaces each garner with another letter correspond to ci pher alphabet. Polyalphabetic substitution is superior than monoalphabetic because polyalphabetic substitutions are apparently more secure than monoalphabetic substitution, because frequency distribution reflects the distribution of the underlying alphabet .Ques3Why are formal write in codeion /decryption method not suitable for bank.Ans Conventional encryption/decryption method is not suitable for bank because it is less secure.If schematic encryption/decryption is exploitation, then the limitation is that the keys must be shared between participants before decryption can occur.If an asymmetric cipher is used instead, altogether in the public eye(predicate) keys need to be shared private keys do not need to be share.Symmetric encryption is the oldest and best-known technique. A secret key, which can be a number, a word, or just a string of random letters, is applied to the text of a message to change the content in a particular way. This capability be as simple as shifting each letter by a number of places in the alphabet. As long as both sender and recipient know the secret key, they can encrypt and decrypt all messages that use this key.Asymmetric Encryption The trouble with secret keys is exchanging them over the Internet or a large network while preventing them from falling into the wrong hands. Anyone who knows the secret key can decrypt the message. genius answer is asymmetric encryption, in which there are two related keysa key pair. A public key is made freely available to anyone who might want to send you a message. A second, private key is kept secret, so that provided you know it.Any message that are encrypted by using the public key can only be decrypted by applying the same algorithm, but by using the matching private key. Any message that is encrypted by using the private key can only be decrypted by using the matching public key.This means that you do not have to worry nearly passing public keys over the Internet . A problem with as ymmetric encryption, however, is that it is slower than symmetric encryption. It requires far more processing power to both encrypt and decrypt the content of the message.Ques4Define types of attack based on what is known to attacker.Ans The following are the cryptological attacks usually performed by an attacker cognize supernumerarytext attackIn a known plaintext attack, an attacker should have both the plaintext and ciphertext of one or more messages. These two items are used to extract the cryptological key and recover the encrypted text.Ciphertext only attackIn this attack, an attacker obtains encrypted messages that have been encrypted using the same encryption algorithm. For example, the original version of WEP used RC4, and if sniffed long enough, the repetitions would lead a hacker to extract the WEP key. Such types of attacks do not require the attacker to have the plaintext because the statistical analysis of the sniffed log is enough.Man-in-the-middle attackIn this f orm of attack, an attacker places himself in the middle of the communications flow between two parties. Once an attacker enters the communications flow, he is able to perform aciphertext only attack, exchange bogus keys, etc.Replay attackIn this type of attack, an attacker tries to repeat or delay a cryptographic transmission. A play back attack can be prevented using session tokens.Chosen plaintext attackIn a chosen plaintext attack, an attacker somehow picks up the information to be encrypted and takes a copy of it with the encrypted data. This is used to find patterns in the cryptographic output that might uncover a vulnerability or reveal a cryptographic key.Chosen ciphertext attackIn this type of attack, an attacker can choose the ciphertext to be decrypted and can then analyze the plaintext output of the event. The early versions of RSA used in SSL were actually vulnerable to this attack.1Cipher text only attackGiven cipher encrypted with same keyC1=Ek (p1) ,C2=Ek(p2)Attacker s find key.2Known plain text attackPlain text is corresponding to the cipher text.Eg P1,C1=Ek(P1) P2,C2=Ek(P2)3Chosen plain text attackPlain text can be chosen that gets encrypted.4Adaptive chosen plain text attackCan modify the plain text choice depending on results of previous encryption.5 Chosen cipher text attackCan choose different cipher texts to be decrypted.Ques6Encrypt the following plaintext by playfair substitution wearediscoveredsaveyourselfAnsPlayfair is a multi-letter encryption which treats diagrams in the plaintext as a single units and translates these units into ciphertext diagrams.The Playfair algo is based on use of 5*5 matrix of letters constructed using a key.Choosen key is WONDERSWONDERS.ABCFGHI/JKLMPQTUVXYZThe matrix is constructed by filling in the letters of the keyword WONDERS from leftfield to right and top to bottom and then filling in the remainder of the matrix with the remaining letters in alphabetic order. The letters I and J count as one letter.Rul es will be 1Repeating plaintext letters that are in same pair are separated with a filler letter .2 Two plaintext letters that fall in the same of matrix are each replaced by the letter to the right circularly .3Two plaintext letters that fall in the same column are each replaced by the letter beneath to it.4Otherwise ,each plaintext letter in a pair is replaced by the letter that lies in its own row and the column occupied by the plaintext letter.Given string is WEAREDISCOVEREDSAVE YOURSELFPlayfair substitution is OWBSWEHGABEBCGKNASXDZWFCOULgtttttttttfygjhvhghjqqQQCh