What specific application layer protocol is primarily used for securely transferring files between a client and a server?

The specific application layer protocol primarily used for securely transferring files between a client and a server is SFTP, which stands for SSH File Transfer Protocol. SFTP is an application layer protocol, meaning it operates at the highest level of the TCP/IP model, directly interacting with end-user applications to provide network services. Its primary function is to enable secure file access, file transfer, and file management capabilities over any reliable data stream. The crucial aspect of SFTP's security comes from its reliance on SSH, or Secure Shell, as its underlying protocol. SSH establishes an encrypted and authenticated connection between the client and the server. Encryption is the process of scrambling data so that only authorized parties can read it, ensuring data confidentiality during transfer. Authentication verifies the identity of both the client and the server, confirming they are who they claim to be, which prevents unauthorized access and "man-in-the-middle" attacks where an attacker intercepts communication. The encrypted tunnel provided by SSH ensures that files, along with commands and all related information like usernames and passwords, are protected from eavesdropping and tampering as they travel across the network. A client, such as an SFTP client application, initiates a connection to an SFTP server. Once the secure SSH session is established and authenticated, the client can then perform various file operations like uploading files from the client to the server, downloading files from the server to the client, deleting files, renaming files, and creating or managing directories on the server. This secure communication channel makes SFTP a robust choice for transferring sensitive data.