<s>
OMEMO	B-Application
is	O
an	O
extension	O
to	O
the	O
Extensible	B-Protocol
Messaging	I-Protocol
and	I-Protocol
Presence	I-Protocol
Protocol	I-Protocol
(	O
XMPP	B-Protocol
)	O
for	O
multi-client	O
end-to-end	O
encryption	O
developed	O
by	O
Andreas	O
Straub	O
.	O
</s>
<s>
According	O
to	O
Straub	O
,	O
OMEMO	B-Application
uses	O
the	O
Double	B-Algorithm
Ratchet	I-Algorithm
Algorithm	I-Algorithm
"	O
to	O
provide	O
multi-end	O
to	O
multi-end	O
encryption	O
,	O
allowing	O
messages	O
to	O
be	O
synchronized	O
securely	O
across	O
multiple	O
clients	O
,	O
even	O
if	O
some	O
of	O
them	O
are	O
offline	O
"	O
.	O
</s>
<s>
The	O
name	O
"	O
OMEMO	B-Application
"	O
is	O
a	O
recursive	O
acronym	O
for	O
"	O
OMEMO	B-Application
Multi-End	O
Message	O
and	O
Object	O
Encryption	O
"	O
.	O
</s>
<s>
It	O
is	O
an	O
open	O
standard	O
based	O
on	O
the	O
Double	B-Algorithm
Ratchet	I-Algorithm
Algorithm	I-Algorithm
and	O
the	O
Personal	O
Eventing	O
Protocol	O
(	O
PEP	O
,	O
XEP-0163	O
)	O
.	O
</s>
<s>
OMEMO	B-Application
offers	O
future	O
and	O
forward	O
secrecy	O
and	O
deniability	O
with	O
message	O
synchronization	O
and	O
offline	O
delivery	O
.	O
</s>
<s>
In	O
comparison	O
with	O
OTR	B-Protocol
,	O
the	O
OMEMO	B-Application
protocol	O
offers	O
many-to-many	O
encrypted	O
chat	O
,	O
offline	O
messages	O
queuing	O
,	O
forward	O
secrecy	O
,	O
file	O
transfer	O
,	O
verifiability	O
and	O
deniability	O
at	O
the	O
cost	O
of	O
slightly	O
larger	O
message	O
size	O
overhead	O
.	O
</s>
<s>
The	O
protocol	O
was	O
developed	O
and	O
first	O
implemented	O
by	O
Andreas	O
Straub	O
as	O
a	O
Google	B-Application
Summer	I-Application
of	I-Application
Code	I-Application
project	O
in	O
2015	O
.	O
</s>
<s>
The	O
project	O
's	O
goal	O
was	O
to	O
implement	O
a	O
double-ratchet-based	O
multi-end	O
to	O
multi-end	O
encryption	O
scheme	O
into	O
an	O
Android	B-Application
XMPP-based	O
instant	O
messaging	O
client	O
called	O
Conversations	B-Protocol
.	O
</s>
<s>
It	O
was	O
introduced	O
in	O
Conversations	B-Protocol
and	O
submitted	O
to	O
the	O
XMPP	B-Protocol
Standards	I-Protocol
Foundation	I-Protocol
(	O
XSF	O
)	O
as	O
a	O
proposed	O
XMPP	B-Protocol
Extension	O
Protocol	O
(	O
XEP	O
)	O
in	O
the	O
autumn	O
of	O
2015	O
and	O
got	O
accepted	O
as	O
in	O
December	O
2016	O
.	O
</s>
<s>
In	O
July	O
2016	O
,	O
the	O
ChatSecure	B-Protocol
project	O
announced	O
that	O
they	O
would	O
implement	O
OMEMO	B-Application
in	O
the	O
next	O
releases	O
.	O
</s>
<s>
ChatSecure	B-Protocol
v4.0	O
supports	O
OMEMO	B-Application
and	O
was	O
released	O
on	O
January	O
17	O
,	O
2017	O
.	O
</s>
<s>
A	O
first	O
experimental	O
release	O
of	O
an	O
OMEMO	B-Application
plugin	O
for	O
the	O
cross-platform	O
XMPP	B-Protocol
client	O
Gajim	B-Language
was	O
made	O
available	O
on	O
December	O
26	O
,	O
2015	O
.	O
</s>
<s>
In	O
June	O
2016	O
,	O
the	O
non-profit	O
computer	O
security	O
consultancy	O
firm	O
Radically	O
Open	O
Security	O
published	O
an	O
analysis	O
of	O
the	O
OMEMO	B-Application
protocol	O
.	O
</s>
<s>
Selected	O
clients	O
supporting	O
OMEMO	B-Application
(	O
full	O
list	O
of	O
clients	O
also	O
exists	O
)	O
:	O
</s>
<s>
XMPPFramework	O
(	O
macOS	B-Application
,	O
iOS	B-Application
,	O
tvOS	B-Operating_System
)	O
supports	O
OMEMO	B-Application
via	O
the	O
OMEMOModule	O
extension	O
when	O
used	O
in	O
conjunction	O
with	O
the	O
SignalProtocol-ObjC	O
library	O
.	O
</s>
