When Alice wants to send confidential email to bob How do they share a symmetric private key?
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Symmetric key cryptography is an application of functions. An encryption function turns readable plain text into unreadable cipher text, and the corresponding decryption function turns the cipher text back into the original plain text. Descriptions of cryptographic protocols are commonly phrased as interactions between Alice, Bob, and Eve. Alice sends a message to Bob, and the eavesdropper Eve listens in on their conversion and tries to break their encryption (Figure 8.2.1). Figure8.2.2.In a symmetric key encryption scheme, Alice and Bob share a common secret, namely the key \(K\text{.}\)In a symmetric key encryption scheme, Alice and Bob first have to agree on a common shared key. Alice uses the key to encrypt a message and sends the encrypted message to Bob. Then, Bob uses the key to decrypt the encrypted message that was sent by Alice in order to obtain the message in its original form (Figure 8.2.2). We introduce Caesar ciphers and other substitution ciphers as examples for symmetric key encryption scheme in the following two sections. Checkpoint8.2.3.Symmetric key cryptography.Complete the following. In a
symmetric encryption protocol select Alice Bob Eve Oscar and select Alice Bob Eve Oscar agree on an encryption method, a decryption method, and a key that is used for encryption and decryption. select Alice Bob Eve Oscar encrypts a message using the encryption method and the key. She sends the encrypted message to
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receives the message from
and decrypts the message using the decryption method and the key. We summarize this introduction to symmetric key cryptography in the video in Figure 8.2.4. How can Alice ensure the confidentiality of a file sent to Bob?Bob can send Alice his public key openly, because he does not care if Eve intercepts it. When Alice wants to send Bob a confidential message, she uses an asymmetric encryption technique to encrypt the data.
How Alice will send an encrypted message to Bob using a common symmetric secret key?In a symmetric key encryption scheme, Alice and Bob first have to agree on a common shared key. Alice uses the key to encrypt a message and sends the encrypted message to Bob. Then, Bob uses the key to decrypt the encrypted message that was sent by Alice in order to obtain the message in its original form (Figure 8.2.
When Alice sends a message to Bob what key will she use to encrypt the message?If Alice sends Bob a message and that message is encrypted with two keys simultaneously: a symmetric key (Ks) and Bob's public key. The symmetric key (Ks) is also sent to Bob, encrypted with the private key of Alice.
How do you share a symmetric key securely?The most common method is to create a shared secret between the two parties by way of diffie hellman key exchange, which is then hashed to create the encryption key.
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