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ccna bangla book pdf free download.The authentication goal of the asymmetric algorithm is reached by starting the encryption process using the private key. This process can be summarized using the following equation: private key (encryption) + public key (decryption) = authenticationWhen the private key is used to encrypt the data, the corresponding public key must be used to decrypt the data. Since only one host has the private key, only that host may encrypt the message, thus providing authentication of the sender. Typically, the secrecy of the public key is not protected, so that any number of hosts can decrypt the message. When a host successfully decrypts a message using the public key, it is assumed that the message was encrypted with the private key, which verifies who the sender is. This is a form of authentication.7.4.1.4 Asymmetric AlgorithmsWhen sending a message, a combination of two encryption phases is required when ensuring the confidentiality, authentication and integrity of the message. Phase 1 - Confidentiality Alice wants to send a message to Bob and make sure that only Bob can read it. In other words, Alice wants to ensure that the messages confidentiality. Alice uses Bob's public key to encrypt the message. Only Bob can decrypt the message using his private key. Phase 2 - Authentication and Integrity Alice also wants to ensure the authentication and integrity of the message. Authentication allows Bob to be sure that the message was sent by Alice, and integrityensures that the message has not been modified. Alice uses her private key to encrypt a hash of the message. Alice sends the encrypted message and the encrypted hash to BoboBob uses Alice's public key to verify that the message has not been modified. The received hash is equal to the hash based on Alice's public key and determined locally. In addition, this verifies that Alice is indeed the sender of the message, since no one else has Alice's private key. Finally, Bob uses his private key to decrypt the message.By sending a message encrypted with Bob's public key and a cryptographic hash encrypted with Alice's private key, confidentiality, authenticity, and integrity are all guaranteed. The following are some of the well-known asymmetric key algorithms available.Diffie-Hellman.Digital Signature Standard (DSS), which contains the Digital Signature Algorithm (DSA).