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linscpSecure file transfer for Linux and Windows
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SSH keys

Create a key pair, convert it to the format linscp reads, and put the public key on the server.

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A key pair replaces your password with something much harder to guess. The private key stays on your computer; the public key goes on the server. When you log in, linscp proves it holds the private key without sending it.

This page uses OpenSSH’s tools for creating keys, because every Linux distribution ships them, and linscp’s own tools for converting and installing.

Create a key pair

Section titled “Create a key pair”
Terminal window
ssh-keygen -t ed25519 -C "alice@laptop"

Accept the default location (~/.ssh/id_ed25519) or give another, and set a passphrase. This creates the private key id_ed25519 and the public key id_ed25519.pub. Ed25519 keys are short, fast and accepted by any current OpenSSH server. Use -t rsa -b 4096 only for servers too old to know Ed25519.

Use the key in linscp

Section titled “Use the key in linscp”

linscp reads private keys in PuTTY’s .ppk format. You can still pick an OpenSSH key:

  1. Open the site’s Advanced Site Settings, page SSH › Authentication.
  2. In Private key file, browse to ~/.ssh/id_ed25519.
  3. linscp sees an OpenSSH key and offers to convert it. Confirm, and choose where to save the .ppk file. The original key is left as it is.

You can also convert on the command line with linscp-cli /keygen:

Terminal window
linscp-cli /keygen ~/.ssh/id_ed25519 /output=$HOME/.ssh/id_ed25519.ppk

The same command changes an existing .ppk key in place: /comment= sets a new comment, /changepassphrase asks for a new passphrase, and /certificate= attaches an OpenSSH certificate. If PuTTY’s puttygen is installed, puttygen ~/.ssh/id_ed25519 -o id_ed25519.ppk does the same conversion.

If the key is loaded into your SSH agent, you do not need a key file at all. See Authentication.

Put the public key on the server

Section titled “Put the public key on the server”

The server must list your public key in ~/.ssh/authorized_keys. Choose one of these ways.

From linscp. On the Authentication page, open Tools and choose Install Public Key into Server…. In a connected session, use Tabs › Install Public Key into Server… instead. Both need SFTP. linscp adds the key to ~/.ssh/authorized_keys and creates ~/.ssh with permissions 700 if it is missing.

From linscp-cli. Pass the key with /copyid, and the site or URL to connect to:

Terminal window
linscp-cli /copyid /identity=$HOME/.ssh/id_ed25519.pub sftp://alice@files.example.org/

With OpenSSH. ssh-copy-id -i ~/.ssh/id_ed25519.pub alice@files.example.org.

By hand. Display Public Key on the Authentication page shows the line to paste into authorized_keys, with a button to copy it.

For the first install you still log in with your password. Afterwards, test a login with the key, then consider turning password logins off on the server.

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