Encrypted Passwords

[Emmanouil Magos <athena . compulink . gr @ compulink . gr>]

..."Even with encryption, a sniffer can still record the encrypted password
and decipher the encrypted password at his leisure. One way around this is
to use an encryption key that involves the current time. If the sender and
receiver are closely synchronized, ths sniffer must replay the encrypted
password within one tick of the two machines' shared clock." ....

Can someone explain this technique to me please?

Thank You
macman @
 compulink .
 gr