I don't have the details, but a modified SSH client could be modified to leak the private key. A modified ssh server can't, since the server never gets the key.

I don't have the details, but a modified SSH client could be modified to leak the private key. A modified ssh server can't, since the server never gets the key. Additionally, from this article: http://www.linuxfordevices.com/c/a/News/Kernelorg-hacked/ http://www.linuxfordevices.com/c/a/News/Kernelorg-hacked/ "Phalanx variants have attacked sensitive Linux systems before by stealing SSH keys to access servers and exploiting kernel vulnerabilities."