cisco 802.1x client

I use the windowsxp client,select the md5-challenge.I get the network
packet. The random sting is "ca 21 f4 62 12 c1 67 c3 5a 09 60 e5 19 13
c9 01" for the RAIDIUS. The password is "123". And the response value
is "a5 56 ba 5e 1c cf ae d3 fc 7e 6e 92 57 d6 38 d8". I use the MD5 to
encrypt the password and I can't get the same result. I am confused
what happend. And what happend about the randow string.
Many thanks