Linux または macOS のクライアント OS から Windows 11 へ公開鍵認証で接続するケースを想定.

Windows で管理者として PowerShell を実行し OpenSSH をインストール

# Install the OpenSSH Server
Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0

# Install the OpenSSH Client
Add-WindowsCapability -Online -Name OpenSSH.Client~~~~0.0.1.0

Windows で OpenSSH Server を起動

# Start the sshd service
Start-Service sshd

# OPTIONAL but recommended:
Set-Service -Name sshd -StartupType 'Automatic'

# Confirm the Firewall rule is configured. It should be created automatically by setup. Run the following to verify
if (!(Get-NetFirewallRule -Name "OpenSSH-Server-In-TCP" -ErrorAction SilentlyContinue | Select-Object Name, Enabled)) {
    Write-Output "Firewall Rule 'OpenSSH-Server-In-TCP' does not exist, creating it..."
    New-NetFirewallRule -Name 'OpenSSH-Server-In-TCP' -DisplayName 'OpenSSH Server (sshd)' -Enabled True -Direction Inbound -Protocol TCP -Action Allow -LocalPort 22
} else {
    Write-Output "Firewall rule 'OpenSSH-Server-In-TCP' has been created and exists."
}

Windows で OpenSSH デフォルトシェルを PowerShell に変更

New-ItemProperty -Path "HKLM:\SOFTWARE\OpenSSH" -Name DefaultShell -Value "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -PropertyType String -Force
Restart-Service sshd

クライアント OS で公開鍵と秘密鍵を作成
```
$ ssh-keygen -t rsa
```

クライアント OS から Windows へ公開鍵をコピー

# Use scp to copy the public key file generated previously on your client to the authorized_keys file on your server
$ scp ~/.ssh/id_rsa.pub username@servername:C:\\ProgramData\\ssh\\administrators_authorized_keys

# Appropriately ACL the authorized_keys file on your server
$ ssh username@servername icacls.exe C:\\ProgramData\\ssh\\administrators_authorized_keys /inheritance:r /grant Administrators:F /grant SYSTEM:F

クライアント OS から Windows へ秘密鍵を用いて接続テスト
```
$ ssh -i ~/.ssh/id_rsa username@servername
```

参考:

https://docs.microsoft.com/ja-jp/windows-server/administration/openssh/openssh_overview
https://docs.microsoft.com/ja-jp/windows-server/administration/openssh/openssh_server_configuration