<s>
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
pre-shared	O
key	O
ciphersuites	O
(	O
TLS-PSK	B-Protocol
)	O
is	O
a	O
set	O
of	O
cryptographic	B-Protocol
protocols	I-Protocol
that	O
provide	O
secure	O
communication	O
based	O
on	O
pre-shared	O
keys	O
(	O
PSKs	O
)	O
.	O
</s>
<s>
These	O
pre-shared	O
keys	O
are	O
symmetric	B-Algorithm
keys	I-Algorithm
shared	O
in	O
advance	O
among	O
the	O
communicating	O
parties	O
.	O
</s>
<s>
There	O
are	O
several	O
cipher	O
suites	O
:	O
The	O
first	O
set	O
of	O
ciphersuites	O
use	O
only	O
symmetric	B-Algorithm
key	I-Algorithm
operations	O
for	O
authentication	O
.	O
</s>
<s>
The	O
second	O
set	O
use	O
a	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
authenticated	O
with	O
a	O
pre-shared	O
key	O
.	O
</s>
<s>
The	O
third	O
set	O
combine	O
public	B-Application
key	I-Application
authentication	O
of	O
the	O
server	O
with	O
pre-shared	O
key	O
authentication	O
of	O
the	O
client	O
.	O
</s>
<s>
Usually	O
,	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
uses	O
public	B-Application
key	I-Application
certificates	O
or	O
Kerberos	B-Protocol
for	O
authentication	O
.	O
</s>
<s>
TLS-PSK	B-Protocol
uses	O
symmetric	B-Algorithm
keys	I-Algorithm
,	O
shared	O
in	O
advance	O
among	O
the	O
communicating	O
parties	O
,	O
to	O
establish	O
a	O
TLS	O
connection	O
.	O
</s>
<s>
Using	O
pre-shared	O
keys	O
can	O
,	O
depending	O
on	O
the	O
ciphersuite	O
,	O
avoid	O
the	O
need	O
for	O
public	B-Application
key	I-Application
operations	O
.	O
</s>
<s>
:	O
"	O
Pre-Shared	O
Key	O
Ciphersuites	O
for	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
"	O
.	O
</s>
<s>
:	O
"	O
Pre-Shared	O
Key	O
(	O
PSK	O
)	O
Ciphersuites	O
with	O
NULL	B-Algorithm
Encryption	I-Algorithm
for	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
"	O
.	O
</s>
<s>
:	O
"	O
Pre-Shared	O
Key	O
Cipher	O
Suites	O
for	O
TLS	O
with	O
SHA-256/384	O
and	O
AES	B-Algorithm
Galois	I-Algorithm
Counter	I-Algorithm
Mode	I-Algorithm
"	O
.	O
</s>
<s>
:	O
"	O
ECDHE_PSK	O
Cipher	O
Suites	O
for	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
"	O
.	O
</s>
