SSH File Transfer Protocol facts for kids
In computing, the SSH File Transfer Protocol (often called SFTP) is a special set of rules, or a network protocol, that helps you move, access, and manage files safely over the internet. It was created by a group called the Internet Engineering Task Force (IETF) to work with the Secure Shell (SSH) protocol. Think of SSH as a secure tunnel for your data. SFTP uses this tunnel to make sure your files are transferred securely.
Even though SFTP is often used with SSH, it can also work with other secure connections, like Transport Layer Security (TLS), which helps keep your online information private. This protocol expects that the connection is already secure and that the server knows who you are.
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What SFTP Can Do
SFTP is much more powerful than older ways of transferring files, like SCP. SCP mostly just lets you copy files. SFTP, however, acts more like a remote file system. This means you can do many things with files on another computer, just like they were on your own!
Here are some cool things SFTP clients can do:
- Restart Transfers: If your internet connection breaks, SFTP can often pick up where it left off.
- List Files: You can see what files and folders are on the remote computer.
- Delete Files: You can remove files from the other computer.
- Handle Different File Types: It works well with all kinds of files, including special ones like symbolic links (shortcuts) on Unix systems.
SFTP is also designed to work smoothly on many different types of computers, unlike SCP, which is mostly used on Unix systems. With SFTP, you can easily stop a file transfer without closing your entire connection.
It's important to remember that SFTP is not the same as FTP running over SSH. It's a completely new protocol built from scratch to be secure. It's also different from the Simple File Transfer Protocol.
SFTP itself doesn't handle security or user logins. It relies on the underlying connection, usually SSH, to keep everything safe and to know who is connecting. When you upload files using SFTP, it can also save important details like when the file was created or changed. This is a big improvement over the older FTP protocol.
How SFTP Was Developed
The Internet Engineering Task Force (IETF) is a group that creates internet standards. They worked on the Secure Shell version 2 protocol and also tried to create a secure way to transfer files using it.
They wrote several "Internet Drafts," which are like early versions of a standard. These drafts helped improve the SFTP protocol over time. Software companies even started using these early versions. As they worked on it, the idea of SFTP grew from just transferring files to also managing and accessing them.
Development paused for a while because some people thought SFTP was becoming too much like a full file system protocol, which was beyond what their group usually focused on. However, work started again later to continue improving it.
Early Versions
Before the IETF got involved, SFTP was a special protocol created by SSH Communications Security in 1997. The first versions (0 to 2) were a bit different from the later ones.
Later Versions
The IETF's goal for SFTP was to make it a standard, secure way to transfer files using SSH-2. They released several drafts, defining different versions of the protocol, like Version 3, Version 4, Version 5, and Version 6. Each new version added improvements and features. For example, Version 6 added ways to lock parts of files and improved how file permissions (called ACLs) were handled.
SFTP Software
You need special software to use SFTP. This software comes in two main types: clients and servers.
SFTP Client
An SFTP client is a computer program that you use to connect to another computer and transfer files. It's like the app on your phone that lets you browse photos on a cloud service. For example, the `sftp` program that comes with OpenSSH is a command-line client.
Some programs, like the `scp` (secure copy) program, can even use both SFTP and SCP protocols, depending on what the server supports. Newer versions of the `scp` program often prefer to use SFTP by default.
SFTP Server
An SFTP server is a program that runs on a computer and waits for SFTP clients to connect. It stores the files and handles the secure transfers. Many SSH servers already include SFTP server capabilities because they share the same default port (port 22). This means if you have an SSH server, you likely have an SFTP server too!
SFTP Proxy
Sometimes, it's hard to control SFTP transfers at the edge of a network, like in a school or company. This is because SFTP traffic is encrypted, making it difficult for regular security tools to see what's happening.
An SFTP proxy is a special tool that can help. Think of it as a security checkpoint for SFTP. It can help log (record) SFTP transfers and even see the actual data being sent, even though it's encrypted. This helps make sure that only allowed files are being moved and that everything is safe.
See also
In Spanish: SSH File Transfer Protocol para niños
