pem文件使用问题

The authenticity of host '35.237.201.179 (35.237.201.179)' can't be established.
ECDSA key fingerprint is SHA256:JJpyIA3d/HdrHAl/sI51oTYvanzxvH0JYNICthQS81Q.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '35.237.201.179' (ECDSA) to the list of known hosts.
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@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
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Permissions 0644 for '/Users/***/Downloads/wifidog-new.pem' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Load key "/Users/***/Downloads/wifidog-new.pem": bad permissions
ubuntu@35.237.201.179: Permission denied (publickey).

解决方法：

chmod 600 /Users/***/Downloads/wifidog-new.pem