<s>
A	O
pseudonymous	B-Protocol
remailer	I-Protocol
or	O
nym	B-Protocol
server	I-Protocol
,	O
as	O
opposed	O
to	O
an	O
anonymous	B-Application
remailer	I-Application
,	O
is	O
an	O
Internet	O
software	O
program	O
designed	O
to	O
allow	O
people	O
to	O
write	O
pseudonymous	O
messages	O
on	O
Usenet	B-Application
newsgroups	O
and	O
send	O
pseudonymous	O
email	O
.	O
</s>
<s>
Unlike	O
purely	O
anonymous	B-Application
remailers	I-Application
,	O
it	O
assigns	O
its	O
users	O
a	O
user	O
name	O
,	O
and	O
it	O
keeps	O
a	O
database	O
of	O
instructions	O
on	O
how	O
to	O
return	O
messages	O
to	O
the	O
real	O
user	O
.	O
</s>
<s>
These	O
instructions	O
usually	O
involve	O
the	O
anonymous	B-Application
remailer	I-Application
network	O
itself	O
,	O
thus	O
protecting	O
the	O
true	O
identity	O
of	O
the	O
user	O
.	O
</s>
<s>
Primordial	O
pseudonymous	B-Protocol
remailers	I-Protocol
once	O
recorded	O
enough	O
information	O
to	O
trace	O
the	O
identity	O
of	O
the	O
real	O
user	O
,	O
making	O
it	O
possible	O
for	O
someone	O
to	O
obtain	O
the	O
identity	O
of	O
the	O
real	O
user	O
through	O
legal	O
or	O
illegal	O
means	O
.	O
</s>
<s>
This	O
form	O
of	O
pseudonymous	B-Protocol
remailer	I-Protocol
is	O
no	O
longer	O
common	O
.	O
</s>
<s>
David	O
Chaum	O
wrote	O
an	O
article	O
in	O
1981	O
that	O
described	O
many	O
of	O
the	O
features	O
present	O
in	O
modern	O
pseudonymous	B-Protocol
remailers	I-Protocol
.	O
</s>
<s>
The	O
Penet	B-Application
remailer	I-Application
,	O
which	O
lasted	O
from	O
1993	O
to	O
1996	O
,	O
was	O
a	O
popular	O
pseudonymous	B-Protocol
remailer	I-Protocol
.	O
</s>
<s>
A	O
nym	B-Protocol
server	I-Protocol
(	O
short	O
for	O
"	O
pseudonym	B-Protocol
server	I-Protocol
"	O
)	O
is	O
a	O
server	B-Application
that	O
provides	O
an	O
untraceable	O
e-mail	O
address	O
,	O
such	O
that	O
neither	O
the	O
nym	B-Protocol
server	I-Protocol
operator	O
nor	O
the	O
operators	O
of	O
the	O
remailers	B-Application
involved	O
can	O
discover	O
which	O
nym	O
corresponds	O
to	O
which	O
real	O
identity	O
.	O
</s>
<s>
To	O
set	O
up	O
a	O
nym	O
,	O
you	O
create	O
a	O
PGP	B-Application
keypair	O
and	O
submit	O
it	O
to	O
the	O
nym	B-Protocol
server	I-Protocol
,	O
along	O
with	O
instructions	O
(	O
called	O
a	O
reply	O
block	O
)	O
to	O
anonymous	B-Application
remailers	I-Application
(	O
such	O
as	O
Cypherpunk	B-Protocol
or	O
Mixmaster	B-Protocol
)	O
on	O
how	O
to	O
send	O
a	O
message	O
to	O
your	O
real	O
address	O
.	O
</s>
<s>
The	O
nym	B-Protocol
server	I-Protocol
returns	O
a	O
confirmation	O
through	O
this	O
reply	O
block	O
.	O
</s>
<s>
To	O
send	O
a	O
message	O
through	O
the	O
nym	B-Protocol
server	I-Protocol
so	O
that	O
the	O
From	O
address	O
is	O
the	O
nym	O
,	O
you	O
add	O
a	O
few	O
headers	O
,	O
sign	O
the	O
message	O
with	O
your	O
nym	O
key	O
,	O
encrypt	O
it	O
with	O
the	O
nym	B-Protocol
server	I-Protocol
key	O
,	O
and	O
send	O
the	O
message	O
to	O
the	O
nym	B-Protocol
server	I-Protocol
,	O
probably	O
routed	O
through	O
some	O
anonymous	B-Application
remailers	I-Application
.	O
</s>
<s>
When	O
the	O
nym	B-Protocol
server	I-Protocol
gets	O
the	O
message	O
,	O
it	O
decrypts	O
the	O
message	O
and	O
sends	O
it	O
on	O
to	O
the	O
intended	O
recipient	O
,	O
with	O
the	O
From	O
:	O
address	O
being	O
your	O
nym	O
.	O
</s>
<s>
When	O
the	O
nym	B-Protocol
server	I-Protocol
gets	O
a	O
message	O
addressed	O
to	O
the	O
nym	O
,	O
it	O
appends	O
it	O
to	O
the	O
nym	O
's	O
reply	O
block	O
and	O
sends	O
it	O
to	O
the	O
first	O
remailer	B-Application
in	O
the	O
chain	O
,	O
which	O
sends	O
it	O
to	O
the	O
next	O
and	O
so	O
on	O
until	O
it	O
reaches	O
your	O
real	O
address	O
.	O
</s>
<s>
It	O
is	O
considered	O
good	O
practice	O
to	O
include	O
instructions	O
to	O
encrypt	O
it	O
on	O
the	O
way	O
,	O
so	O
that	O
someone	O
(	O
or	O
some	O
organization	O
)	O
doing	O
in/out	O
traffic	O
analysis	O
on	O
the	O
nym	B-Protocol
server	I-Protocol
cannot	O
easily	O
match	O
the	O
message	O
received	O
by	O
you	O
to	O
the	O
one	O
sent	O
by	O
the	O
nym	B-Protocol
server	I-Protocol
.	O
</s>
<s>
Existing	O
"	O
multi-use	O
reply	O
block	O
"	O
nym	B-Protocol
servers	I-Protocol
were	O
shown	O
to	O
be	O
susceptible	O
to	O
passive	O
traffic	O
analysis	O
with	O
one	O
month	O
's	O
worth	O
of	O
incoming	O
spam	O
(	O
based	O
on	O
2005	O
figures	O
)	O
in	O
a	O
paper	O
by	O
Bram	O
Cohen	O
,	O
Len	O
Sassaman	O
,	O
and	O
Nick	O
Mathewson	O
.	O
</s>
