<s>
SPKAC	B-General_Concept
is	O
an	O
acronym	O
that	O
stands	O
for	O
Signed	O
Public	B-Application
Key	I-Application
and	O
Challenge	O
,	O
also	O
known	O
as	O
Netscape	B-Protocol
SPKI	O
.	O
</s>
<s>
It	O
is	O
a	O
format	O
for	O
sending	O
a	O
Certification	O
Signing	O
Request	O
:	O
it	O
encodes	O
a	O
public	B-Application
key	I-Application
,	O
that	O
can	O
be	O
manipulated	O
using	O
OpenSSL	B-Language
.	O
</s>
<s>
It	O
is	O
created	O
using	O
the	O
little	O
documented	O
HTML	O
keygen	O
element	O
inside	O
a	O
number	O
of	O
Netscape	B-Protocol
compatible	I-Protocol
browsers	I-Protocol
.	O
</s>
<s>
There	O
exists	O
an	O
ongoing	O
effort	O
to	O
standardise	O
SPKAC	B-General_Concept
through	O
an	O
Internet	O
Draft	O
in	O
the	O
Internet	O
Engineering	O
Task	O
Force	O
(	O
IETF	O
)	O
.	O
</s>
<s>
The	O
purpose	O
of	O
this	O
work	O
has	O
been	O
to	O
formally	O
define	O
what	O
has	O
existed	O
prior	O
as	O
a	O
de	O
facto	O
standard	O
,	O
and	O
to	O
address	O
security	O
deficiencies	O
,	O
particular	O
with	O
respect	O
to	O
historic	O
insecure	O
use	O
of	O
MD5	B-Algorithm
that	O
has	O
since	O
been	O
declared	O
unsafe	O
for	O
use	O
with	O
digital	O
signatures	O
as	O
per	O
RFC	O
6151	O
.	O
</s>
<s>
HTML5	O
originally	O
specified	O
the	O
<keygen>	O
element	O
to	O
support	O
SPKAC	B-General_Concept
in	O
the	O
browser	O
to	O
make	O
it	O
easier	O
to	O
create	O
client	B-Protocol
side	I-Protocol
certificates	O
through	O
a	O
web	O
service	O
for	O
protocols	O
such	O
as	O
WebID	O
;	O
however	O
,	O
subsequent	O
work	O
for	O
HTML	O
5.1	O
placed	O
the	O
keygen	O
element	O
"	O
at-risk	O
"	O
,	O
and	O
the	O
first	O
public	O
working	O
draft	O
of	O
HTML	O
5.2	O
removes	O
the	O
keygen	O
element	O
entirely	O
.	O
</s>
<s>
An	O
implementation	O
for	O
Erlang/OTP	B-Operating_System
exists	O
too	O
.	O
</s>
<s>
An	O
implementation	O
for	O
Python	B-Language
is	O
named	O
pyspkac	O
.	O
</s>
<s>
PHP	O
OpenSSL	B-Language
extension	O
as	O
of	O
version	O
5.6.0	O
.	O
</s>
