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.The string of numbers generated by anetwork information in a raw state by dumping thePRNG is not actually random, however, since PRNGshexadecimal representation of each byte in a packet.operate using deterministic mathematical formulas.Some analyzers translate such information into Ameri��Based on some initial seed, a complicated mathematicalcan Standard Code for Information Interchangeprocess is typically used to generate a string of numbers(ASCII) for easier reading of data payloads and identifythat has the same statistical distribution as perfectly ran��different fields in header bytes using labels for eachdom numbers generated from a natural process such asfield.Many analyzers support various query options forradioactive decay.The hitch is that if the same seed isfiltering different types of traffic to find the type ofreused sometime later, the identical string of  randominformation the user is looking for more easily.digits is produced by the PRNG, which is why the wordpseudo (meaning  false in appearance ) is used toMarketplacedescribe the process.There are protocol analyzers available on the market forevery kind of networking technology around, includingIn order for pseudorandom numbers to be truly random,Ethernet, wireless, Asynchronous Transfer Modea different random seed must be specified each time the(ATM), Fiber Channel, Small Computer System Inter-PRNG is used.A typical way to generate such a seed onPface (SCSI), and serial connections.A market leader ina computer system is to combine together informationcommercial products is Network Associates with itsfrom several real-time sources including the internalSniffer line of analyzer tools.Other vendors of protocolclock, the location of the mouse pointer, the size of aanalyzers include Frontline Test Equipment,currently open file on the hard drive, and so on.ThisLANSleuth, and Logix Communications.Some popu��information is then hashed using a one-way function tolar free protocol analyzers include Ethereal, EtherPeek,create a fixed-length seed that is entered into the PRNGSnort, Tcpdump, and Windump.Microsoft Windowsand used to generate a unique and unpredictable string2000 includes a limited-feature version of Networkof (essentially) random numbers.Monitor, a protocol analyzer whose full version is partSee Also: cryptography, encryption algorithmof System Management Server (SMS), a distributedsystems management platform from Microsoft.public keyNotesA key known to everyone in a public key cryptographyOther names commonly used for protocol analyzers aresystem.network analyzer, monitor, and packet sniffer.Theterm Sniffer is actually a trademark of Network Asso��ciates, but sniffer and sniffing are as widely used257public key cryptography public key cryptographyOverview �% Shamir Three PassEach user in a public key cryptography system has two�% Massey-Omurakeys: a private key known only to the user and a publickey available for anyone who wants to obtain it.Typi�� �% Efficient Probabilistic Public Key Encryptioncally, public keys are used for the following purposes: (EPOK)�% Encrypting messages sent to other users who then Implementationdecrypt them using their own private key In public key cryptography, each user is issued a pair ofkeys: a public key available to anyone who requests it,�% Verifying digital signatures attached to messages toand a private key known only to the user who owns it.Ifprove that the messages integrity is intactone of these two keys is used to encrypt a message, theSee Also: key, public key, public key cryptography other can be used to decrypt it.In order for user A toencrypt a message and send it to user B, user A couldfirst obtain user B s public key (which is readily availablepublic key cryptographysomewhere) and encrypts the message using this key.An encryption scheme that allows private communica��User A then sends the encrypted message to user B, whotions to take place without prior existence of a shareddecrypts it using its own private key (since user B s pri��secret.vate key can undo whatever user B s public key has done).OverviewAlthough public key systems could be used that way forTraditional or secret key cryptography relies on theencrypting communication between users, in practiceexistence of a shared secret known by the partiesthey are not used this way.Instead, public key cryptog��involved.Secret key cryptography is highly private, butraphy is generally used to securely exchange a sessionthe weakness in this system is securely exchanging thiskey (a secret key used only for a single communicationsecret between the two parties, a necessary step beforesession and then discarded) between the two users, andencrypted communications can be performed betweenonce both parties have this session key they can use it toparties and a difficult task to complete.Public key cryp��encrypt and decrypt messages sent between them.Thistography solves this problem by providing a way tois done because public keys are much longer (1024 bitsshare a secret between two parties over an insecure pub��or more) than secret keys (56 to 256 bits, typically), andlic connection such as the Internet [ Pobierz całość w formacie PDF ]