Draw Model For Network Security Computer Science Essay

Draw Model For Nedeucerk Security Computer science EssaySENDER Sender transfer message to other troupe by some sort of internet. RECEIVER Receiver receives message enrapture by sender through some sort of internet. Trusted third gear party trusted third party is needed o vouch the message transmits from one party to another. Third party distributes secret data to twain the parties. Third party actually provides authenticity of message transmission. obstructor An opponent hindquarters be a human or a virus that fuel harm the transmitted message going through some sort of internet.Secure message It is a message to which a secret key is apply which is not in readable by opponent.Secret information Secret information is a key applied to message.Ques2Why is polyalphabetic heterotaxy superior to monoalphatic substitution.autonomic nervous system Polyalphabetic ciphers use multiple substitution alphabetic.A monoalphabetic substitution replaces severally letter with another lette r harmonize to cipher alphabet. Polyalphabetic substitution is superior than monoalphabetic because polyalphabetic substitutions ar app arntly more plug than monoalphabetic substitution, because frequency distribution reflects the distribution of the underlying alphabet .Ques3Why are conventional encoding / decipherion method not suitable for posit.autonomic nervous system Conventional encryption/decryption method is not suitable for bank because it is less secure.If conventional encryption/decryption is using, then the limitation is that the keys essential be divided up between participants before decryption stooge occur.If an noninterchangeable cipher is use instead, totally reality keys need to be shared insular 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 letter, is applied to the schoolbook of a message to change the content in a finical way. This ki ng be as simple as shifting distributively letter by a number of places in the alphabet. As coherent as both sender and recipient know the secret key, they can encrypt and decrypt all messages that use this key.A radiate work oution The line with secret keys is exchanging them over the Internet or a large vane while preventing them from falling into the wrong hands. Anyone who knows the secret key can decrypt the message. One answer is asymmetric encryption, in which there are two related keysa key dyad. A public key is made freely available to anyone who might want to send you a message. A second, clannish key is kept secret, so that only 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 factor that you do not have to worry about passing public keys over the Internet . A problem with asymmetric 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 assailant.Ans The following are the cryptanalytic attacks usually performed by an attackerknow plain school schoolbook attackIn a known plaintext attack, an attacker should have both the plaintext and ciphertext of one or more messages. These two items are apply to plagiarize the cryptographic 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 allow 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 lumbe r is enough.Man-in-the-middle attackIn this form 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, etceteraReplay attackIn this type of attack, an attacker tries to repeat or delay a cryptographic transmission. A replay 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 use up 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 encr ypted with same keyC1=Ek (p1) ,C2=Ek(p2)Attackers find key.2Known plain text attack translucent text is check 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 garner constructed using a key.Choosen key is WONDERSWONDERS.ABCFGHI/JKLMPQTUVXYZThe matrix is constructed by filling in the earn of the keyword WONDERS from left 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.Rules will be 1Repeating plaintext letters that are in same pair are separated with a filler letter .2 both 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 editorial 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