一般ssh都必須要輸入密碼才可以登入遠端系統主機，如果因為某些理由不想輸入密碼的話，可以利用交換密鑰來達到認證的方式：
假設現在有
假設現在有
- 遠端伺服器
- 近端伺服器Server B
使用者想從ServerB連線到ServerA伺服器而不使用密碼，則可以在ServerB執行以下指令：
ssh-keygen -t rsa (指定產生的密鑰類型)
Generating public/private rsa key pair.
Enter file in which to save the key (/home/wales/.ssh/id_rsa): <<金鑰放置的地點>>
Created directory '/home/wales/.ssh'.
Enter passphrase (empty for no passphrase): <<輸入金鑰密碼，請留空白>>
Enter same passphrase again: <<再輸入一次密碼>>
Your identification has been saved in /home/wales/.ssh/id_rsa.
Your public key has been saved in /home/wales/.ssh/id_rsa.pub.
The key fingerprint is:xx:xx:xx:xx:xx:xx
之後在/home/wales/.ssh/會產生兩個檔案id_rsa及id_rsa.pub：
id_rsa.pub記載著公鑰的資訊，請將此公鑰發佈到ServerA，並儲存到/home/wales/.ssh/authorized_keys
完成設定之後，回到ServerB並執行ssh wales@serverA
The authenticity of host 'serverA' can't be established.
RSA key fingerprint is
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'serverA' (RSA) to the list of known hosts.
wales@serverA's password:
輸入這次密碼後 下次就不會再詢問了。
附註：在/etc/ssh/sshd_conf 底下的StrictModes要改為no，並重開sshd服務
