User a is writing a sensitive email message to user b outside the local network. user a has chosen to use pki to secure his message and ensure only user b can read the sensitive email. at what layer of the osi layer does the encryption and decryption of the message take place?

Encryption and decryption takes place at Presentation layer of OSI model.

Explanation:

For a secure means of communication the term used widely is PKIPKI stands for "public key infrastructure".PKI is the framework of encryption for security of communication between the server(A) and client(B).It consists two keys: Public key and Private key.Encryption is a process in which plain text is encoded into cipher text using algorithms and ciphers. This is done so that the message may be read only by the intended reader and it may remain secure.Decryption on the other hand is the reverse process of encryption. In decryption, a cipher text is translated back into plain text using keys or ciphers provided by the sender.Presentation layer also called syntax layer is the 6th layer of OSI model. It presents the data to application layer in a standardized and well defined form. All the encryption/decryption of data is done in this layer.

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