~/.ssh/authorized keys

• touch ~/.ssh/authorized_keys && chmod og-r ~/.ssh/authorized_keys
• chmod 600 ~/.ssh/authorized_keys or chmod ogw-r ~/.ssh/authorized_keys

chown 

• Configure OpenSSH to allow Public-key authentication

sshd_config

#AuthorizedKeysFile	.ssh/authorized_keys .ssh/authorized_keys

https://linux.die.net/man/5/sshd_config sshd_config

AUTHORIZED_KEYS FILE FORMAT
    AuthorizedKeysFile specifies the files containing public keys for public key authentication; if this option is not specified, the default is ~/.ssh/authorized_keys and
    ~/.ssh/authorized_keys2.  Each line of the file contains one key (empty lines and lines starting with a ‘#’ are ignored as comments).  Public keys consist of the following
    space-separated fields: options, keytype, base64-encoded key, comment.  The options field is optional.  The supported key 
types are:

          [email protected]
          ecdsa-sha2-nistp256
          ecdsa-sha2-nistp384
          ecdsa-sha2-nistp521
          [email protected]
          ssh-ed25519
          ssh-dss
          ssh-rsa

    The comment field is not used for anything (but may be convenient for the user to identify the key).

Example files

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIEBiBqpWXhPTH9RIo9UR3ED9xUv6O/SqpWRn16UH/gHD TEXT@TEXT
ssh-rsa .../...

Additional information about format key:

https://serverfault.com/questions/526399/why-do-my-two-ssh-public-keys-have-the-same-beginning/526404

https://tools.ietf.org/html/rfc4253

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQ...
      |  "ssh-rsa"   |exponent|   modulus

ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFKy...
          |   "ssh-ed25519"   |   32 byte public key

Errors

sshd logs

Apr 26 11:45:37 ip-10-10-10-10.eu-west-1.compute.internal sshd[18174]: Authentication refused: bad ownership or modes for file /home/your_user/.ssh/authorized_keys

Related terms

• sftp configuration
• expiry-time in OpenSSH 7.7 (2018)
• ssh-import-id
• AuthenticationMethods
• visudo

See also

• OpenSSH (changelog): /etc/ssh/sshd_config | /etc/ssh/ssh_config | ~/.ssh/ | openSSL | sshd logs | sftp | scp | authorized_keys | ssh-keygen | ssh-keyscan | ssh-add | ssh-agent | ssh | Ssh -O stop | ssh-copy-id | CheckHostIP | UseKeychain, OpenSSF
• SSH: ssh, TLS, .ppk, .pem, .crt, .pub, ED25519, Key exchange method (KEX), public key, private key, ssh -Q kex, IAMUserSSHKeys, known_hosts, ssh tunnel, Dropbear