Panasonic DP-8020E Service Manual page 461

Challenge Response
<1896.697170952@svr.pcc.co.jp>
Digest parameter, Challenge + PASSWD
<1896.697170952@svr.pcc.co.jp>PASSWD
Produces a 16 octet digest value of
c4c9334bac560ecc979e58001b3e22fb
The POP3 client makes note of this timestamp, and then issues the APOP command. The "name''
parameter has identical semantics to the "name" parameter of the USER command. The "digest" parameter
is calculated by applying the MD5 algorithm to a string consisting of the timestamp (including angle-
brackets) followed by a shared secret. This shared secret is a string known only to the POP3 client and
server. Great care should be taken to prevent unauthorized disclosure of the secret, as knowledge of the
secret will allow any entity to successfully masquerade as the named user. The "digest" parameter
itself is a 16-octet value which is sent in hexadecimal format, using lower-case ASCII characters.
When the POP3 server receives the APOP command, it verifies the digest provided. If the digest is correct,
the POP3 server issues a positive response, and the POP3 session enters the TRANSACTION state.
Otherwise, a negative response is issued and the POP3 session remains in the AUTHORIZATION state.
Note that as the length of the shared secret increases, so does the difficulty of deriving it.
Ver. 1.0
Client
Establish TCP connection (TCP port No. 110)
+OK POP3 server ready <1896.697170952@svr.pcc.co.jp>
APOP USER c4c9334bac560ecc979e58001b3e22fb
+OK maildrop has 1 message (369 octets)
Continue to follow the POP3 procedure
APOP overview
461
STAT
+OK 1
DP-8020E/8020P/8016P
Server
Possible Responses:
+OK
-ERR permission denied
SEP 2006