为了提高scp的传输速度指定了scp的加密算法为arcfour
$ scp -c arcfour localFile userName@remoteIP:remoteFile 得到报错unknown cipher type
$ ssh -c userName@remoteIP 得到报错no matching cipher found

解决办法：找到/etc/ssh/sshd_config，在文件最后加入一行
Ciphers 3des-cbc,blowfish-cbc,cast128-cbc,arcfour,arcfour128,arcfour256,aes128-cbc,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com