...
Handling
...
the
...
IdP
...
Private
...
Key
...
This
...
topic
...
discusses
...
the
...
proper
...
handling
...
of
...
the
...
IdP's
...
private
...
signing
...
key.
...
The
...
corresponding
...
public
...
key
...
is
...
bound
...
to
...
an
...
...
...
...
...
...
.
...
Note
...
that
...
a
...
signing
...
key
...
may
...
be
...
used
...
for
...
more
...
than
...
just
...
signing,
...
as
...
discussed
...
in
...
the
...
...
...
topic.
...
See
...
the
...
...
...
...
topic
...
regarding
...
keys
...
and
...
certificates
...
used
...
for
...
browser-facing
...
TLS.
...
The
...
IdP's
...
private
...
signing
...
key
...
is
...
used
...
to
...
sign
...
SAML
...
assertions
...
transmitted
...
to
...
the
...
SP.
...
(The
...
corresponding
...
certificate
...
in
...
metadata
...
contains
...
the
...
public
...
key
...
that
...
is
...
used
...
by
...
the
...
SP
...
to
...
verify
...
the
...
signature
...
on
...
the
...
assertion.)
...
If
...
the
...
private
...
key
...
is
...
lost
...
or
...
stolen,
...
the
...
holder
...
has
...
the
...
power
...
to
...
issue
...
arbitrary
...
assertions
...
to
...
any
...
SP.
...
This
...
is
...
the
...
absolute
...
worst
...
thing
...
that
...
can
...
happen
...
in
...
a
...
federated
...
context.
| Warning | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| =
|
|
|
| ||||||
| } Positive control of your private keys must be maintained at all times. This includes the private keys used for browser-facing TLS as well as your private signing key. {warning} |
The
...
IdP's
...
private
...
signing
...
key
...
is
...
necessarily
...
an
...
online
...
key,
...
that
...
is,
...
it
...
must
...
be
...
available
...
to
...
the
...
IdP
...
software
...
at
...
runtime.
...
An
...
online
...
key
...
may
...
be
...
encrypted,
...
but
...
the
...
password
...
or
...
passphrase
...
used
...
to
...
decrypt
...
the
...
key
...
generally
...
has
...
to
...
be
...
available
...
in
...
an
...
unencrypted
...
file
...
so
...
that
...
the
...
IdP
...
service
...
can
...
be
...
restarted
...
in
...
unattended
...
fashion.
...
Therefore
...
an
...
online
...
key
...
is
...
considerably
...
more
...
vulnerable
...
than
...
an
...
offline
...
key,
...
and
...
must
...
be
...
protected
...
accordingly.
...
If
...
the
...
signing
...
key
...
is
...
stored
...
in
...
the
...
file
...
system
...
as
...
an
...
ordinary
...
file,
...
it
...
should
...
have
...
strict
...
permissions
...
to
...
prevent
...
unauthorized
...
copying
...
of
...
the
...
private
...
key.
...
For
...
stronger
...
protection,
...
the
...
signing
...
key
...
may
...
be
...
stored
...
in
...
a
...
hardware
...
security
...
module
...
(HSM)
...
that
...
prevents
...
export
...
of
...
the
...
private
...
key.
...
Key
...
Audit
...
You
...
need
...
to
...
go
...
back
...
to
...
day
...
one
...
of
...
the
...
total
...
lifetime
...
of
...
each
...
of
...
your
...
private
...
keys
...
and
...
ask
...
the
...
following
...
question:
...
Has
...
this
...
key
...
been
...
under
...
my
...
positive
...
control
...
at
...
all
...
times?
...
If
...
the
...
answer
...
to
...
that
...
question
...
is
...
anything
...
other
...
than
...
yes,
...
the
...
key
...
should
...
be
...
considered
...
compromised.
...
This
...
requires
...
you
...
to
...
securely
...
generate
...
a
...
new
...
private
...
key
...
and
...
to
...
systematically
...
migrate
...
the
...
corresponding
...
public
...
key
...
certificate
...
out
...
of
...
metadata.
...
See
...
the
...
...
...
topic
...
for
...
safe
...
instructions
...
how
...
to
...
do
...
this.
...
If
...
there
...
is
...
reason
...
to
...
believe
...
that
...
the
...
IdP's
...
signing
...
key
...
has
...
fallen
...
into
...
the
...
wrong
...
hands,
...
it
...
should
...
be
...
replaced
...
immediately.
...
In
...
this
...
case,
...
there
...
can
...
be
...
no
...
orderly
...
migration
...
of
...
the
...
corresponding
...
public
...
key
...
certificate
...
in
...
metadata,
...
which
...
should
...
also
...
be
...
replaced
...
immediately.
...
This
...
will
...
break
...
interoperability
...
with
...
SPs
...
until
...
such
...
time
...
as
...
they
...
have
...
refreshed
...
metadata
...
(which
...
is
...
why
...
regular,
...
automated
...
metadata
...
refresh
...
is
...
important),
...
so
...
replace
...
the
...
IdP's
...
signing
...
key
...
only
...
under
...
the
...
most
...
serious
...
circumstances.
...
Key
...
Generation
...
See
...
the
...
...
...
topic
...
for
...
instructions
...
how
...
to
...
generate
...
a
...
secure
...
private
...
signing
...
key
...
for
...
your
...
IdP.
...