blacklisting the bad ssh keys?

michael taylor mctylr at
Thu May 22 13:19:43 EDT 2008

On Wed, May 14, 2008 at 7:52 PM, Steven M. Bellovin <smb at> wrote:
> Given the published list of bad ssh keys due to the Debian mistake (see
>, should sshd be
> updated to contain a blacklist of those keys?  I suspect that a Bloom
> filter would be quite compact and efficient.

Debian has two packages, one call openssh-blacklist (1024 DSA and 2048
bit keys RSA keys) ~4MB, and an "unstable" package
openssh-blacklist-extra for non-default key sizes sizes that are
simple lists of blacklisted keys.

current source:

from the README:
The blacklists are separate by architecture, type, and bit size.  The
contents are ordered by process pid, starting at PID 1 and ending at PID

While generating entries, each possible process ID must be used.  To
help automate this, LD_PRELOAD is used to override the getpid() libc
function.  See "" for details.  Note that the list
is architecture-specific.


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