“known_hosts”條目的不同部分是什麼意思？

下面是一個known_hosts條目。開頭ssh-rsa和結尾的部分是公鑰。其他部分（前面的字元ssh-rsa）是什麼？

| 1 | KnbIIJIPrL / 1p7ofUV74sK + J /立方厘米= | wrjOFnPgoF0afgH0PeRtRqSdgvc = SSH-RSA AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdnm9tUDbO9IDSwBK6TbQa + PXYPCPy6rbTrTtw7PHkccKrpp0yVhp5HdEIcKr6pLlVDBfOLX9QUsyCOV0wzfjIJNlGEYsdlLJizHhbn2mUjvSAHQqZETYP81eFzLQNnPHt4EVVUh7VfDESU84KezmD5QlWpXLmvU31 / YMF + Se8xhHTvKSCZIFImWwoG6mbUoWf9nzpIoaSjB + weqqUUmpaaasXVal72J + UX2B + 2RPW3RcT0eOzQgqlJL3RKrTJvdsjE3JEAvGq3lGHSZXy28G3skua2SmVi / w4yCE6gbODqnTWlg7 + wC604ydGXA8VJiS5ap43JXiUFFAaQ ==

是|1|HASH_MAGIC，表明它是一個散列的 known_hosts 條目。

接下來的兩個 base-64 編碼欄位（由 分隔|）是隨機生成的鹽和主機的 SHA-1 雜湊。

如果您使用的是舊版本的 OpenSSH，或者您已HashKnownHosts No在/etc/ssh/ssh_config或 ~/.ssh/config 中設置，則條目不會經過雜湊處理，看起來更像這樣：

remotehostname,192.168.1.100 ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAq2A7hRGmdn...etc...

從sshd(8)手冊頁的SSH_KNOWN_HOSTS FILE FORMAT部分：

 Each line in these files contains the following fields: markers
 (optional), hostnames, bits, exponent, modulus, comment.  The fields are
 separated by spaces.

…

 Alternately, hostnames may be stored in a hashed form which hides host
 names and addresses should the file’s contents be disclosed.  Hashed
 hostnames start with a ‘|’ character.  Only one hashed hostname may
 appear on a single line and none of the above negation or wildcard opera-
 tors may be applied.

引用自：https://serverfault.com/questions/331080