question regarding portsnap

Wed Nov 26 00:08:19 PST 2008

Im running FreeBSD 7.0-RELEASE #0
The OS was downloaded from freebsd.org two months ago.

When I am trying to upgrade ports by using portsnap, portsnap doesn't work.

# portsnap fetch
Looking up portsnap.FreeBSD.org mirrors... 3 mirrors found.
Fetching public key from portsnap1.freebsd.org... key has incorrect hash.
Fetching public key from portsnap2.freebsd.org... key has incorrect hash.
Fetching public key from portsnap4.freebsd.org... key has incorrect hash.
No mirrors remaining, giving up.

Why the key is incorrect and what can be done to resolve this issue?  Please answer ASAP.