What can I do if someone tampers with my SSH public key?












3















I understand private keys being compromised is a huge risk; however, what about public keys. If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?






linux encryption







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  • Your public key is supposed to be shared. It is the key that encrypts the data, your private key, decrypts the data.

    – Ramhound
    3 hours ago
















3















I understand private keys being compromised is a huge risk; however, what about public keys. If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?






linux encryption







share|improve this question

























  • Your public key is supposed to be shared. It is the key that encrypts the data, your private key, decrypts the data.

    – Ramhound
    3 hours ago














3












3








3








I understand private keys being compromised is a huge risk; however, what about public keys. If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?






linux encryption







share|improve this question
















I understand private keys being compromised is a huge risk; however, what about public keys. If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?






linux encryption




linux encryption






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 4 hours ago









JakeGould

31.6k1097139




31.6k1097139










asked 4 hours ago









KevKev

162




162













  • Your public key is supposed to be shared. It is the key that encrypts the data, your private key, decrypts the data.

    – Ramhound
    3 hours ago



















  • Your public key is supposed to be shared. It is the key that encrypts the data, your private key, decrypts the data.

    – Ramhound
    3 hours ago

















Your public key is supposed to be shared. It is the key that encrypts the data, your private key, decrypts the data.

– Ramhound
3 hours ago





Your public key is supposed to be shared. It is the key that encrypts the data, your private key, decrypts the data.

– Ramhound
3 hours ago










2 Answers
2






active

oldest

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5














You can always regenerate a public key as long as you have the private key.



You ask:




If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?




So is the situation you are concerned about something like you leave your computer on, don’t put it to sleep, run away to do something, then someone goes to your computer and just adds a few characters to your public key so it is effectively damaged? Or even deletes it?



No worries as long as you have your private key. Just run this command:



ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub


And your public key will be regenerated. Just note that the comment at the end of the public key line that allows you to more easily identify which key is what—via what is typically an email address—won’t be added to this id_rsa.pub via this method. So you might want to open it up in a text editor and manually add that.



About your other concerns.



Now if you are concerned about someone hacking the public key on a remote machine in a way that denies you access? Honestly, you would have a fairly larger issue to deal with in a case like that.



Typically, someone would need to be able to gain root access on a machine to do that. And that is not unheard of but a rare occurrence at best.






share|improve this answer

































    4














    The whole point of a public key is to be widely known. It can be vetted by the PKI (public key infrastructure). You can sign messages (and other things) with your private key locally on your PC, and others can confirm that the message came from you.



    Similarly, the public key can be put into the SSH config files on remote servers. When you SSH into those servers, they present a challenge that can only be correctly answered by someone with the proper private key.



    Your original question asked:




    "If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it"...




    then it would no longer be the same public key. You can regenerate the public key immediately for another admin to set the proper public key.



    You have secondary worries: Who else can get access to my machine, what can they do, and how do I recover? hose answers are complicated and situational.



    There are many good resources on SSH and PKI on the web... here's a good start: SSH Essentials: Working with SSH Servers, Clients, and Keys






    share|improve this answer

























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      2 Answers
      2






      active

      oldest

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      2 Answers
      2






      active

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      active

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      active

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      5














      You can always regenerate a public key as long as you have the private key.



      You ask:




      If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?




      So is the situation you are concerned about something like you leave your computer on, don’t put it to sleep, run away to do something, then someone goes to your computer and just adds a few characters to your public key so it is effectively damaged? Or even deletes it?



      No worries as long as you have your private key. Just run this command:



      ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub


      And your public key will be regenerated. Just note that the comment at the end of the public key line that allows you to more easily identify which key is what—via what is typically an email address—won’t be added to this id_rsa.pub via this method. So you might want to open it up in a text editor and manually add that.



      About your other concerns.



      Now if you are concerned about someone hacking the public key on a remote machine in a way that denies you access? Honestly, you would have a fairly larger issue to deal with in a case like that.



      Typically, someone would need to be able to gain root access on a machine to do that. And that is not unheard of but a rare occurrence at best.






      share|improve this answer






























        5














        You can always regenerate a public key as long as you have the private key.



        You ask:




        If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?




        So is the situation you are concerned about something like you leave your computer on, don’t put it to sleep, run away to do something, then someone goes to your computer and just adds a few characters to your public key so it is effectively damaged? Or even deletes it?



        No worries as long as you have your private key. Just run this command:



        ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub


        And your public key will be regenerated. Just note that the comment at the end of the public key line that allows you to more easily identify which key is what—via what is typically an email address—won’t be added to this id_rsa.pub via this method. So you might want to open it up in a text editor and manually add that.



        About your other concerns.



        Now if you are concerned about someone hacking the public key on a remote machine in a way that denies you access? Honestly, you would have a fairly larger issue to deal with in a case like that.



        Typically, someone would need to be able to gain root access on a machine to do that. And that is not unheard of but a rare occurrence at best.






        share|improve this answer




























          5












          5








          5







          You can always regenerate a public key as long as you have the private key.



          You ask:




          If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?




          So is the situation you are concerned about something like you leave your computer on, don’t put it to sleep, run away to do something, then someone goes to your computer and just adds a few characters to your public key so it is effectively damaged? Or even deletes it?



          No worries as long as you have your private key. Just run this command:



          ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub


          And your public key will be regenerated. Just note that the comment at the end of the public key line that allows you to more easily identify which key is what—via what is typically an email address—won’t be added to this id_rsa.pub via this method. So you might want to open it up in a text editor and manually add that.



          About your other concerns.



          Now if you are concerned about someone hacking the public key on a remote machine in a way that denies you access? Honestly, you would have a fairly larger issue to deal with in a case like that.



          Typically, someone would need to be able to gain root access on a machine to do that. And that is not unheard of but a rare occurrence at best.






          share|improve this answer















          You can always regenerate a public key as long as you have the private key.



          You ask:




          If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it, wouldn’t that prevent me access to the server; therefor, affecting availability on my end?




          So is the situation you are concerned about something like you leave your computer on, don’t put it to sleep, run away to do something, then someone goes to your computer and just adds a few characters to your public key so it is effectively damaged? Or even deletes it?



          No worries as long as you have your private key. Just run this command:



          ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub


          And your public key will be regenerated. Just note that the comment at the end of the public key line that allows you to more easily identify which key is what—via what is typically an email address—won’t be added to this id_rsa.pub via this method. So you might want to open it up in a text editor and manually add that.



          About your other concerns.



          Now if you are concerned about someone hacking the public key on a remote machine in a way that denies you access? Honestly, you would have a fairly larger issue to deal with in a case like that.



          Typically, someone would need to be able to gain root access on a machine to do that. And that is not unheard of but a rare occurrence at best.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited 4 hours ago

























          answered 4 hours ago









          JakeGouldJakeGould

          31.6k1097139




          31.6k1097139

























              4














              The whole point of a public key is to be widely known. It can be vetted by the PKI (public key infrastructure). You can sign messages (and other things) with your private key locally on your PC, and others can confirm that the message came from you.



              Similarly, the public key can be put into the SSH config files on remote servers. When you SSH into those servers, they present a challenge that can only be correctly answered by someone with the proper private key.



              Your original question asked:




              "If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it"...




              then it would no longer be the same public key. You can regenerate the public key immediately for another admin to set the proper public key.



              You have secondary worries: Who else can get access to my machine, what can they do, and how do I recover? hose answers are complicated and situational.



              There are many good resources on SSH and PKI on the web... here's a good start: SSH Essentials: Working with SSH Servers, Clients, and Keys






              share|improve this answer






























                4














                The whole point of a public key is to be widely known. It can be vetted by the PKI (public key infrastructure). You can sign messages (and other things) with your private key locally on your PC, and others can confirm that the message came from you.



                Similarly, the public key can be put into the SSH config files on remote servers. When you SSH into those servers, they present a challenge that can only be correctly answered by someone with the proper private key.



                Your original question asked:




                "If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it"...




                then it would no longer be the same public key. You can regenerate the public key immediately for another admin to set the proper public key.



                You have secondary worries: Who else can get access to my machine, what can they do, and how do I recover? hose answers are complicated and situational.



                There are many good resources on SSH and PKI on the web... here's a good start: SSH Essentials: Working with SSH Servers, Clients, and Keys






                share|improve this answer




























                  4












                  4








                  4







                  The whole point of a public key is to be widely known. It can be vetted by the PKI (public key infrastructure). You can sign messages (and other things) with your private key locally on your PC, and others can confirm that the message came from you.



                  Similarly, the public key can be put into the SSH config files on remote servers. When you SSH into those servers, they present a challenge that can only be correctly answered by someone with the proper private key.



                  Your original question asked:




                  "If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it"...




                  then it would no longer be the same public key. You can regenerate the public key immediately for another admin to set the proper public key.



                  You have secondary worries: Who else can get access to my machine, what can they do, and how do I recover? hose answers are complicated and situational.



                  There are many good resources on SSH and PKI on the web... here's a good start: SSH Essentials: Working with SSH Servers, Clients, and Keys






                  share|improve this answer















                  The whole point of a public key is to be widely known. It can be vetted by the PKI (public key infrastructure). You can sign messages (and other things) with your private key locally on your PC, and others can confirm that the message came from you.



                  Similarly, the public key can be put into the SSH config files on remote servers. When you SSH into those servers, they present a challenge that can only be correctly answered by someone with the proper private key.



                  Your original question asked:




                  "If someone were to access my public key associated with the private key I use to SSH in the Linux server, and modify it"...




                  then it would no longer be the same public key. You can regenerate the public key immediately for another admin to set the proper public key.



                  You have secondary worries: Who else can get access to my machine, what can they do, and how do I recover? hose answers are complicated and situational.



                  There are many good resources on SSH and PKI on the web... here's a good start: SSH Essentials: Working with SSH Servers, Clients, and Keys







                  share|improve this answer














                  share|improve this answer



                  share|improve this answer








                  edited 4 hours ago









                  JakeGould

                  31.6k1097139




                  31.6k1097139










                  answered 4 hours ago









                  Christopher HostageChristopher Hostage

                  3,5501028




                  3,5501028






























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