SSH with authentication and no privacy

[coderman]

Previous threads have discussed the now deprecated NONE cipher and the
rationale for its removal.  Recent posts on FCC compliance indicate
the usefulness of authentication without privacy for packet radio.

I also find this useful for transfers between IPsec protected
endpoints.  Authentication is then useful for user
administration/privileges but encryption is not necessary given the
IPsec transport.

Is there a compromise that would be acceptable to the ssh maintainers
which provides an authenticated ssh mode without privacy?  IPsec has
long been able to support such a mode (AH without ESP) and there is a
legitimate need as mentioned before.

Concern for accidental disclosure due to user error or
misconfiguration is legitimate.  Would the following changes be
acceptable?

- Require an ssh[d]_config option which explicitly allows
authentication without privacy.  This would be defaulted to off /
commented in the example config files.

- Require an ssh/scp/* flag on command line to enable authentication
without privacy (in addition to config file approval).  HPN uses the
'-z' option.

- When used in this mode a message would be printed to stderr
indicating the lack of privacy.  HPN prints a 'WARNING: ENABLED NULL
CIPHER' for scp but not ssh.  Perhaps 'WARNING: privacy is disabled,
plaintext mode selected' would be more explanatory.

I would be willing to work on such a patch if this would address
maintainer concerns about unintended disclosure while providing the
useful feature of authentication without privacy.

Best regards,