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What role does the user@host that often appears at the end of a public ssh-rsa key play? Is it necessary? Does if serve any purpose in the authentication, or is it simply a record of who and where the key was created by for the information purposes (for a human reader)?

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up vote 6 down vote accepted

It's merely a comment. You can put anything you'd like there. Or nothing at all.

Most key generators put user@host there to help identify on what host the key was generated, and for which user.

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Thanks, that is exactly what I wanted to know. I assume the key is delimited from the comment with white space, and the keys are separated from each other with new lines? – usedTobeaMember Mar 18 '14 at 13:35
Yes, correct on both counts. – EEAA Mar 18 '14 at 13:35
man authorized_keys will explain you the fieldss yo'ure allowed to use : extra-parameters(command, from, etc) whitespace type-of-key(ssh-rsa,ssh-dsa) whitespace key whitespace comments. – mveroone Mar 18 '14 at 13:39
@Kwaio I don't have that ManPage. – usedTobeaMember Mar 18 '14 at 18:51
sorry, mine redirects to man sshd, then look for "AUTHORIZED_KEYS FILE FORMAT" chapter – mveroone Mar 20 '14 at 15:23

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