<s>
A	O
blockchain	B-Application
is	O
a	O
distributed	B-Architecture
ledger	B-Language
with	O
growing	O
lists	O
of	O
records	O
(	O
blocks	O
)	O
that	O
are	O
securely	O
linked	O
together	O
via	O
cryptographic	B-Algorithm
hashes	I-Algorithm
.	O
</s>
<s>
Each	O
block	O
contains	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
of	O
the	O
previous	O
block	O
,	O
a	O
timestamp	B-Operating_System
,	O
and	O
transaction	O
data	O
(	O
generally	O
represented	O
as	O
a	O
Merkle	B-Algorithm
tree	I-Algorithm
,	O
where	O
data	B-Data_Structure
nodes	I-Data_Structure
are	O
represented	O
by	O
leaves	O
)	O
.	O
</s>
<s>
The	O
timestamp	B-Operating_System
proves	O
that	O
the	O
transaction	O
data	O
existed	O
when	O
the	O
block	O
was	O
created	O
.	O
</s>
<s>
Since	O
each	O
block	O
contains	O
information	O
about	O
the	O
previous	O
block	O
,	O
they	O
effectively	O
form	O
a	O
chain	O
(	O
compare	O
linked	B-Data_Structure
list	I-Data_Structure
data	O
structure	O
)	O
,	O
with	O
each	O
additional	O
block	O
linking	O
to	O
the	O
ones	O
before	O
it	O
.	O
</s>
<s>
Consequently	O
,	O
blockchain	B-Application
transactions	B-General_Concept
are	O
irreversible	O
in	O
that	O
,	O
once	O
they	O
are	O
recorded	O
,	O
the	O
data	O
in	O
any	O
given	O
block	O
cannot	O
be	O
altered	O
retroactively	O
without	O
altering	O
all	O
subsequent	O
blocks	O
.	O
</s>
<s>
Blockchains	B-Application
are	O
typically	O
managed	O
by	O
a	O
peer-to-peer	O
(	O
P2P	O
)	O
computer	O
network	O
for	O
use	O
as	O
a	O
public	O
distributed	B-Architecture
ledger	B-Language
,	O
where	O
nodes	O
collectively	O
adhere	O
to	O
a	O
consensus	B-Operating_System
algorithm	I-Operating_System
protocol	O
to	O
add	O
and	O
validate	O
new	O
transaction	O
blocks	O
.	O
</s>
<s>
Although	O
blockchain	B-Application
records	O
are	O
not	O
unalterable	O
,	O
since	O
blockchain	B-Application
forks	O
are	O
possible	O
,	O
blockchains	B-Application
may	O
be	O
considered	O
secure	O
by	O
design	O
and	O
exemplify	O
a	O
distributed	B-Architecture
computing	I-Architecture
system	O
with	O
high	O
Byzantine	B-Operating_System
fault	I-Operating_System
tolerance	I-Operating_System
.	O
</s>
<s>
A	O
blockchain	B-Application
was	O
created	O
by	O
a	O
person	O
(	O
or	O
group	O
of	O
people	O
)	O
using	O
the	O
name	O
(	O
or	O
pseudonym	O
)	O
Satoshi	O
Nakamoto	O
in	O
2008	O
to	O
serve	O
as	O
the	O
public	O
distributed	B-Architecture
ledger	B-Language
for	O
bitcoin	B-General_Concept
cryptocurrency	O
transactions	B-General_Concept
,	O
based	O
on	O
previous	O
work	O
by	O
Stuart	O
Haber	O
,	O
W	O
.	O
Scott	O
Stornetta	O
,	O
and	O
Dave	O
Bayer	O
.	O
</s>
<s>
The	O
implementation	O
of	O
the	O
blockchain	B-Application
within	O
bitcoin	B-General_Concept
made	O
it	O
the	O
first	O
digital	O
currency	O
to	O
solve	O
the	O
double-spending	B-Operating_System
problem	O
without	O
the	O
need	O
of	O
a	O
trusted	O
authority	O
or	O
central	O
server	B-Application
.	O
</s>
<s>
The	O
bitcoin	B-General_Concept
design	O
has	O
inspired	O
other	O
applications	O
and	O
blockchains	B-Application
that	O
are	O
readable	O
by	O
the	O
public	O
and	O
are	O
widely	O
used	O
by	O
cryptocurrencies	O
.	O
</s>
<s>
The	O
blockchain	B-Application
may	O
be	O
considered	O
a	O
type	O
of	O
payment	O
rail	O
.	O
</s>
<s>
Private	O
blockchains	B-Application
have	O
been	O
proposed	O
for	O
business	O
use	O
.	O
</s>
<s>
Computerworld	O
called	O
the	O
marketing	O
of	O
such	O
privatized	O
blockchains	B-Application
without	O
a	O
proper	O
security	O
model	O
"	O
snake	O
oil	O
"	O
;	O
however	O
,	O
others	O
have	O
argued	O
that	O
permissioned	O
blockchains	B-Application
,	O
if	O
carefully	O
designed	O
,	O
may	O
be	O
more	O
decentralized	B-Operating_System
and	O
therefore	O
more	O
secure	O
in	O
practice	O
than	O
permissionless	O
ones	O
.	O
</s>
<s>
Cryptographer	O
David	O
Chaum	O
first	O
proposed	O
a	O
blockchain-like	O
protocol	O
in	O
his	O
1982	O
dissertation	O
"	O
Computer	O
Systems	O
Established	O
,	O
Maintained	O
,	O
and	O
Trusted	O
by	O
Mutually	O
Suspicious	O
Groups.	O
"	O
</s>
<s>
In	O
1992	O
,	O
Haber	O
,	O
Stornetta	O
,	O
and	O
Dave	O
Bayer	O
incorporated	O
Merkle	B-Algorithm
trees	I-Algorithm
into	O
the	O
design	O
,	O
which	O
improved	O
its	O
efficiency	O
by	O
allowing	O
several	O
document	O
certificates	O
to	O
be	O
collected	O
into	O
one	O
block	O
.	O
</s>
<s>
Under	O
their	O
company	O
Surety	O
,	O
their	O
document	O
certificate	O
hashes	B-Error_Name
have	O
been	O
published	O
in	O
The	O
New	O
York	O
Times	O
every	O
week	O
since	O
1995	O
.	O
</s>
<s>
The	O
first	O
decentralized	B-Operating_System
blockchain	B-Application
was	O
conceptualized	O
by	O
a	O
person	O
(	O
or	O
group	O
of	O
people	O
)	O
known	O
as	O
Satoshi	O
Nakamoto	O
in	O
2008	O
.	O
</s>
<s>
Nakamoto	O
improved	O
the	O
design	O
in	O
an	O
important	O
way	O
using	O
a	O
Hashcash-like	O
method	O
to	O
timestamp	B-Operating_System
blocks	O
without	O
requiring	O
them	O
to	O
be	O
signed	O
by	O
a	O
trusted	O
party	O
and	O
introducing	O
a	O
difficulty	O
parameter	O
to	O
stabilize	O
the	O
rate	O
at	O
which	O
blocks	O
are	O
added	O
to	O
the	O
chain	O
.	O
</s>
<s>
The	O
design	O
was	O
implemented	O
the	O
following	O
year	O
by	O
Nakamoto	O
as	O
a	O
core	O
component	O
of	O
the	O
cryptocurrency	O
bitcoin	B-General_Concept
,	O
where	O
it	O
serves	O
as	O
the	O
public	O
ledger	B-Language
for	O
all	O
transactions	B-General_Concept
on	O
the	O
network	O
.	O
</s>
<s>
In	O
August	O
2014	O
,	O
the	O
bitcoin	B-General_Concept
blockchain	B-Application
file	O
size	O
,	O
containing	O
records	O
of	O
all	O
transactions	B-General_Concept
that	O
have	O
occurred	O
on	O
the	O
network	O
,	O
reached	O
20GB	O
(	O
gigabytes	O
)	O
.	O
</s>
<s>
In	O
January	O
2015	O
,	O
the	O
size	O
had	O
grown	O
to	O
almost	O
30GB	O
,	O
and	O
from	O
January	O
2016	O
to	O
January	O
2017	O
,	O
the	O
bitcoin	B-General_Concept
blockchain	B-Application
grew	O
from	O
50GB	O
to	O
100GB	O
in	O
size	O
.	O
</s>
<s>
The	O
ledger	B-Language
size	O
had	O
exceeded	O
200	O
GB	O
by	O
early	O
2020	O
.	O
</s>
<s>
The	O
words	O
block	O
and	O
chain	O
were	O
used	O
separately	O
in	O
Satoshi	O
Nakamoto	O
's	O
original	O
paper	O
,	O
but	O
were	O
eventually	O
popularized	O
as	O
a	O
single	O
word	O
,	O
blockchain	B-Application
,	O
by	O
2016	O
.	O
</s>
<s>
According	O
to	O
Accenture	O
,	O
an	O
application	B-Application
of	O
the	O
diffusion	O
of	O
innovations	O
theory	O
suggests	O
that	O
blockchains	B-Application
attained	O
a	O
13.5	O
%	O
adoption	O
rate	O
within	O
financial	O
services	O
in	O
2016	O
,	O
therefore	O
reaching	O
the	O
early	O
adopters	O
 '	O
phase	O
.	O
</s>
<s>
Industry	O
trade	O
groups	O
joined	O
to	O
create	O
the	O
Global	O
Blockchain	B-Application
Forum	O
in	O
2016	O
,	O
an	O
initiative	O
of	O
the	O
Chamber	O
of	O
Digital	O
Commerce	O
.	O
</s>
<s>
In	O
May	O
2018	O
,	O
Gartner	O
found	O
that	O
only	O
1%	O
of	O
CIOs	O
indicated	O
any	O
kind	O
of	O
blockchain	B-Application
adoption	O
within	O
their	O
organisations	O
,	O
and	O
only	O
8%	O
of	O
CIOs	O
were	O
in	O
the	O
short-term	O
"	O
planning	O
or	O
[	O
looking	O
at ]	O
active	O
experimentation	O
with	O
blockchain	B-Application
"	O
.	O
</s>
<s>
For	O
the	O
year	O
2019	O
Gartner	O
reported	O
5%	O
of	O
CIOs	O
believed	O
blockchain	B-Application
technology	I-Application
was	O
a	O
'	O
game-changer	O
'	O
for	O
their	O
business	O
.	O
</s>
<s>
A	O
blockchain	B-Application
is	O
a	O
decentralized	B-Operating_System
,	O
distributed	B-Architecture
,	O
and	O
often	O
public	O
,	O
digital	O
ledger	B-Language
consisting	O
of	O
records	O
called	O
blocks	O
that	O
are	O
used	O
to	O
record	O
transactions	B-General_Concept
across	O
many	O
computers	O
so	O
that	O
any	O
involved	O
block	O
cannot	O
be	O
altered	O
retroactively	O
,	O
without	O
the	O
alteration	O
of	O
all	O
subsequent	O
blocks	O
.	O
</s>
<s>
This	O
allows	O
the	O
participants	O
to	O
verify	O
and	O
audit	O
transactions	B-General_Concept
independently	O
and	O
relatively	O
inexpensively	O
.	O
</s>
<s>
A	O
blockchain	B-Application
database	O
is	O
managed	O
autonomously	O
using	O
a	O
peer-to-peer	O
network	O
and	O
a	O
distributed	B-Architecture
timestamping	O
server	B-Application
.	O
</s>
<s>
Such	O
a	O
design	O
facilitates	O
robust	B-Application
workflow	B-Operating_System
where	O
participants	O
 '	O
uncertainty	O
regarding	O
data	O
security	O
is	O
marginal	O
.	O
</s>
<s>
The	O
use	O
of	O
a	O
blockchain	B-Application
removes	O
the	O
characteristic	O
of	O
infinite	O
reproducibility	O
from	O
a	O
digital	O
asset	O
.	O
</s>
<s>
It	O
confirms	O
that	O
each	O
unit	O
of	O
value	O
was	O
transferred	O
only	O
once	O
,	O
solving	O
the	O
long-standing	O
problem	O
of	O
double-spending	B-Operating_System
.	O
</s>
<s>
A	O
blockchain	B-Application
has	O
been	O
described	O
as	O
a	O
value-exchange	O
protocol	O
.	O
</s>
<s>
A	O
blockchain	B-Application
can	O
maintain	O
title	O
rights	O
because	O
,	O
when	O
properly	O
set	O
up	O
to	O
detail	O
the	O
exchange	O
agreement	O
,	O
it	O
provides	O
a	O
record	O
that	O
compels	O
offer	O
and	O
acceptance	O
.	O
</s>
<s>
Logically	O
,	O
a	O
blockchain	B-Application
can	O
be	O
seen	O
as	O
consisting	O
of	O
several	O
layers	O
:	O
</s>
<s>
Blocks	O
hold	O
batches	O
of	O
valid	O
transactions	B-General_Concept
that	O
are	O
hashed	O
and	O
encoded	O
into	O
a	O
Merkle	B-Algorithm
tree	I-Algorithm
.	O
</s>
<s>
Each	O
block	O
includes	O
the	O
cryptographic	B-Algorithm
hash	I-Algorithm
of	O
the	O
prior	O
block	O
in	O
the	O
blockchain	B-Application
,	O
linking	O
the	O
two	O
.	O
</s>
<s>
This	O
iterative	B-Algorithm
process	O
confirms	O
the	O
integrity	O
of	O
the	O
previous	O
block	O
,	O
all	O
the	O
way	O
back	O
to	O
the	O
initial	O
block	O
,	O
which	O
is	O
known	O
as	O
the	O
genesis	O
block	O
(	O
Block	O
0	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
a	O
secure	O
hash-based	O
history	O
,	O
any	O
blockchain	B-Application
has	O
a	O
specified	O
algorithm	O
for	O
scoring	O
different	O
versions	O
of	O
the	O
history	O
so	O
that	O
one	O
with	O
a	O
higher	O
score	O
can	O
be	O
selected	O
over	O
others	O
.	O
</s>
<s>
Blockchains	B-Application
are	O
typically	O
built	O
to	O
add	O
the	O
score	O
of	O
new	O
blocks	O
onto	O
old	O
blocks	O
and	O
are	O
given	O
incentives	O
to	O
extend	O
with	O
new	O
blocks	O
rather	O
than	O
overwrite	O
old	O
blocks	O
.	O
</s>
<s>
For	O
example	O
,	O
bitcoin	B-General_Concept
uses	O
a	O
proof-of-work	O
system	O
,	O
where	O
the	O
chain	O
with	O
the	O
most	O
cumulative	O
proof-of-work	O
is	O
considered	O
the	O
valid	O
one	O
by	O
the	O
network	O
.	O
</s>
<s>
Within	O
a	O
blockchain	B-Application
the	O
computation	O
is	O
carried	O
out	O
redundantly	O
rather	O
than	O
in	O
the	O
traditional	O
segregated	O
and	O
parallel	B-Operating_System
manner	O
.	O
</s>
<s>
The	O
block	O
time	O
is	O
the	O
average	O
time	O
it	O
takes	O
for	O
the	O
network	O
to	O
generate	O
one	O
extra	O
block	O
in	O
the	O
blockchain	B-Application
.	O
</s>
<s>
In	O
cryptocurrency	O
,	O
this	O
is	O
practically	O
when	O
the	O
transaction	O
takes	O
place	O
,	O
so	O
a	O
shorter	O
block	O
time	O
means	O
faster	O
transactions	B-General_Concept
.	O
</s>
<s>
The	O
block	O
time	O
for	O
Ethereum	B-Application
is	O
set	O
to	O
between	O
14	O
and	O
15	O
seconds	O
,	O
while	O
for	O
bitcoin	B-General_Concept
it	O
is	O
on	O
average	O
10	O
minutes	O
.	O
</s>
<s>
By	O
storing	O
data	O
across	O
its	O
peer-to-peer	O
network	O
,	O
the	O
blockchain	B-Application
eliminates	O
some	O
risks	O
that	O
come	O
with	O
data	O
being	O
held	O
centrally	O
.	O
</s>
<s>
The	O
decentralized	B-Operating_System
blockchain	B-Application
may	O
use	O
ad	O
hoc	O
message	B-Architecture
passing	I-Architecture
and	O
distributed	B-Architecture
networking	B-Application
.	O
</s>
<s>
In	O
a	O
so-called	O
"	O
51%	O
attack	O
"	O
a	O
central	O
entity	O
gains	O
control	O
of	O
more	O
than	O
half	O
of	O
a	O
network	O
and	O
can	O
then	O
manipulate	O
that	O
specific	O
blockchain	B-Application
record	O
at	O
will	O
,	O
allowing	O
double-spending	B-Operating_System
.	O
</s>
<s>
Blockchain	B-Application
security	O
methods	O
include	O
the	O
use	O
of	O
public-key	B-Application
cryptography	I-Application
.	O
</s>
<s>
A	O
public	B-Application
key	I-Application
(	O
a	O
long	O
,	O
random-looking	O
string	O
of	O
numbers	O
)	O
is	O
an	O
address	O
on	O
the	O
blockchain	B-Application
.	O
</s>
<s>
A	O
private	B-Application
key	I-Application
is	O
like	O
a	O
password	O
that	O
gives	O
its	O
owner	O
access	O
to	O
their	O
digital	O
assets	O
or	O
the	O
means	O
to	O
otherwise	O
interact	O
with	O
the	O
various	O
capabilities	O
that	O
blockchains	B-Application
now	O
support	O
.	O
</s>
<s>
Data	O
stored	O
on	O
the	O
blockchain	B-Application
is	O
generally	O
considered	O
incorruptible	O
.	O
</s>
<s>
Every	O
node	B-Protocol
in	O
a	O
decentralized	B-Operating_System
system	O
has	O
a	O
copy	O
of	O
the	O
blockchain	B-Application
.	O
</s>
<s>
Data	O
quality	O
is	O
maintained	O
by	O
massive	O
database	O
replication	B-Architecture
and	O
computational	O
trust	O
.	O
</s>
<s>
Transactions	B-General_Concept
are	O
broadcast	B-Operating_System
to	O
the	O
network	O
using	O
the	O
software	O
.	O
</s>
<s>
Early	O
blockchains	B-Application
rely	O
on	O
energy-intensive	O
mining	O
nodes	O
to	O
validate	O
transactions	B-General_Concept
,	O
add	O
them	O
to	O
the	O
block	O
they	O
are	O
building	O
,	O
and	O
then	O
broadcast	B-Operating_System
the	O
completed	O
block	O
to	O
other	O
nodes	O
.	O
</s>
<s>
Blockchains	B-Application
use	O
various	O
time-stamping	O
schemes	O
,	O
such	O
as	O
proof-of-work	O
,	O
to	O
serialize	O
changes	O
.	O
</s>
<s>
Later	O
consensus	B-Operating_System
methods	O
include	O
proof	B-Protocol
of	I-Protocol
stake	I-Protocol
.	O
</s>
<s>
The	O
growth	O
of	O
a	O
decentralized	B-Operating_System
blockchain	B-Application
is	O
accompanied	O
by	O
the	O
risk	O
of	O
centralization	O
because	O
the	O
computer	O
resources	O
required	O
to	O
process	O
larger	O
amounts	O
of	O
data	O
become	O
more	O
expensive	O
.	O
</s>
<s>
Finality	O
is	O
the	O
level	O
of	O
confidence	O
that	O
the	O
well-formed	O
block	O
recently	O
appended	O
to	O
the	O
blockchain	B-Application
will	O
not	O
be	O
revoked	O
in	O
the	O
future	O
(	O
is	O
"	O
finalized	O
"	O
)	O
and	O
thus	O
can	O
be	O
trusted	O
.	O
</s>
<s>
Most	O
distributed	B-Architecture
blockchain	B-Application
protocols	O
,	O
whether	O
proof	O
of	O
work	O
or	O
proof	B-Protocol
of	I-Protocol
stake	I-Protocol
,	O
cannot	O
guarantee	O
the	O
finality	O
of	O
a	O
freshly	O
committed	O
block	O
,	O
and	O
instead	O
rely	O
on	O
"	O
probabilistic	O
finality	O
"	O
:	O
as	O
the	O
block	O
goes	O
deeper	O
into	O
a	O
blockchain	B-Application
,	O
it	O
is	O
less	O
likely	O
to	O
be	O
altered	O
or	O
reverted	O
by	O
a	O
newly	O
found	O
consensus	B-Operating_System
.	O
</s>
<s>
Byzantine	O
fault	O
tolerance-based	O
proof-of-stake	B-Protocol
protocols	O
purport	O
to	O
provide	O
so	O
called	O
"	O
absolute	O
finality	O
"	O
:	O
a	O
randomly	O
chosen	O
validator	O
proposes	O
a	O
block	O
,	O
the	O
rest	O
of	O
validators	O
vote	O
on	O
it	O
,	O
and	O
,	O
if	O
a	O
supermajority	O
decision	O
approves	O
it	O
,	O
the	O
block	O
is	O
irreversibly	O
committed	O
into	O
the	O
blockchain	B-Application
.	O
</s>
<s>
A	O
modification	O
of	O
this	O
method	O
,	O
an	O
"	O
economic	O
finality	O
"	O
,	O
is	O
used	O
in	O
practical	O
protocols	O
,	O
like	O
the	O
Casper	O
protocol	O
used	O
in	O
Ethereum	B-Application
:	O
validators	O
which	O
sign	O
two	O
different	O
blocks	O
at	O
the	O
same	O
position	O
in	O
the	O
blockchain	B-Application
are	O
subject	O
to	O
"	O
slashing	O
"	O
,	O
where	O
their	O
leveraged	O
stake	O
is	O
forfeited	O
.	O
</s>
<s>
Open	O
blockchains	B-Application
are	O
more	O
user-friendly	B-General_Concept
than	O
some	O
traditional	O
ownership	O
records	O
,	O
which	O
,	O
while	O
open	O
to	O
the	O
public	O
,	O
still	O
require	O
physical	O
access	O
to	O
view	O
.	O
</s>
<s>
Because	O
all	O
early	O
blockchains	B-Application
were	O
permissionless	O
,	O
controversy	O
has	O
arisen	O
over	O
the	O
blockchain	B-Application
definition	O
.	O
</s>
<s>
An	O
issue	O
in	O
this	O
ongoing	O
debate	O
is	O
whether	O
a	O
private	O
system	O
with	O
verifiers	O
tasked	O
and	O
authorized	O
(	O
permissioned	O
)	O
by	O
a	O
central	O
authority	O
should	O
be	O
considered	O
a	O
blockchain	B-Application
.	O
</s>
<s>
Proponents	O
of	O
permissioned	O
or	O
private	O
chains	O
argue	O
that	O
the	O
term	O
"	O
blockchain	B-Application
"	O
may	O
be	O
applied	O
to	O
any	O
data	O
structure	O
that	O
batches	O
data	O
into	O
time-stamped	O
blocks	O
.	O
</s>
<s>
These	O
blockchains	B-Application
serve	O
as	O
a	O
distributed	B-Architecture
version	O
of	O
multiversion	B-Operating_System
concurrency	I-Operating_System
control	I-Operating_System
(	O
MVCC	O
)	O
in	O
databases	O
.	O
</s>
<s>
Just	O
as	O
MVCC	O
prevents	O
two	O
transactions	B-General_Concept
from	O
concurrently	O
modifying	O
a	O
single	O
object	O
in	O
a	O
database	O
,	O
blockchains	B-Application
prevent	O
two	O
transactions	B-General_Concept
from	O
spending	O
the	O
same	O
single	O
output	O
in	O
a	O
blockchain	B-Application
.	O
</s>
<s>
Opponents	O
say	O
that	O
permissioned	O
systems	O
resemble	O
traditional	O
corporate	O
databases	O
,	O
not	O
supporting	O
decentralized	B-Operating_System
data	O
verification	O
,	O
and	O
that	O
such	O
systems	O
are	O
not	O
hardened	O
against	O
operator	O
tampering	O
and	O
revision	O
.	O
</s>
<s>
Nikolai	O
Hampton	O
of	O
Computerworld	O
said	O
that	O
"	O
many	O
in-house	O
blockchain	B-Application
solutions	O
will	O
be	O
nothing	O
more	O
than	O
cumbersome	O
databases	O
,	O
"	O
and	O
"	O
without	O
a	O
clear	O
security	O
model	O
,	O
proprietary	O
blockchains	B-Application
should	O
be	O
eyed	O
with	O
suspicion.	O
"	O
</s>
<s>
An	O
advantage	O
to	O
an	O
open	O
,	O
permissionless	O
,	O
or	O
public	O
,	O
blockchain	B-Application
network	O
is	O
that	O
guarding	O
against	O
bad	O
actors	O
is	O
not	O
required	O
and	O
no	O
access	O
control	O
is	O
needed	O
.	O
</s>
<s>
This	O
means	O
that	O
applications	O
can	O
be	O
added	O
to	O
the	O
network	O
without	O
the	O
approval	O
or	O
trust	O
of	O
others	O
,	O
using	O
the	O
blockchain	B-Application
as	O
a	O
transport	B-Architecture
layer	I-Architecture
.	O
</s>
<s>
Bitcoin	B-General_Concept
and	O
other	O
cryptocurrencies	O
currently	O
secure	O
their	O
blockchain	B-Application
by	O
requiring	O
new	O
entries	O
to	O
include	O
proof	O
of	O
work	O
.	O
</s>
<s>
To	O
prolong	O
the	O
blockchain	B-Application
,	O
bitcoin	B-General_Concept
uses	O
Hashcash	O
puzzles	O
.	O
</s>
<s>
In	O
2016	O
,	O
venture	O
capital	O
investment	O
for	O
blockchain-related	O
projects	O
was	O
weakening	O
in	O
the	O
USA	O
but	O
increasing	O
in	O
China	O
.	O
</s>
<s>
Bitcoin	B-General_Concept
and	O
many	O
other	O
cryptocurrencies	O
use	O
open	O
(	O
public	O
)	O
blockchains	B-Application
.	O
</s>
<s>
,	O
bitcoin	B-General_Concept
has	O
the	O
highest	O
market	O
capitalization	O
.	O
</s>
<s>
Permissioned	O
blockchains	B-Application
use	O
an	O
access	O
control	O
layer	O
to	O
govern	O
who	O
has	O
access	O
to	O
the	O
network	O
.	O
</s>
<s>
It	O
has	O
been	O
argued	O
that	O
permissioned	O
blockchains	B-Application
can	O
guarantee	O
a	O
certain	O
level	O
of	O
decentralization	O
,	O
if	O
carefully	O
designed	O
,	O
as	O
opposed	O
to	O
permissionless	O
blockchains	B-Application
,	O
which	O
are	O
often	O
centralized	O
in	O
practice	O
.	O
</s>
<s>
Nikolai	O
Hampton	O
argued	O
in	O
Computerworld	O
that	O
"	O
There	O
is	O
also	O
no	O
need	O
for	O
a	O
'	O
51	O
percent	O
 '	O
attack	O
on	O
a	O
private	O
blockchain	B-Application
,	O
as	O
the	O
private	O
blockchain	B-Application
(	O
most	O
likely	O
)	O
already	O
controls	O
100	O
percent	O
of	O
all	O
block	O
creation	O
resources	O
.	O
</s>
<s>
If	O
you	O
could	O
attack	O
or	O
damage	O
the	O
blockchain	B-Application
creation	O
tools	O
on	O
a	O
private	O
corporate	O
server	B-Application
,	O
you	O
could	O
effectively	O
control	O
100	O
percent	O
of	O
their	O
network	O
and	O
alter	O
transactions	B-General_Concept
however	O
you	O
wished.	O
"	O
</s>
<s>
This	O
has	O
a	O
set	O
of	O
particularly	O
profound	O
adverse	O
implications	O
during	O
a	O
financial	O
crisis	O
or	O
debt	O
crisis	O
like	O
the	O
financial	O
crisis	O
of	O
2007	O
–	O
08	O
,	O
where	O
politically	O
powerful	O
actors	O
may	O
make	O
decisions	O
that	O
favor	O
some	O
groups	O
at	O
the	O
expense	O
of	O
others	O
,	O
and	O
"	O
the	O
bitcoin	B-General_Concept
blockchain	B-Application
is	O
protected	O
by	O
the	O
massive	O
group	O
mining	O
effort	O
.	O
</s>
<s>
It	O
's	O
unlikely	O
that	O
any	O
private	O
blockchain	B-Application
will	O
try	O
to	O
protect	O
records	O
using	O
gigawatts	O
of	O
computing	O
power	O
—	O
it	O
's	O
time-consuming	O
and	O
expensive.	O
"	O
</s>
<s>
He	O
also	O
said	O
,	O
"	O
Within	O
a	O
private	O
blockchain	B-Application
there	O
is	O
also	O
no	O
'	O
race	O
 '	O
;	O
there	O
's	O
no	O
incentive	O
to	O
use	O
more	O
power	O
or	O
discover	O
blocks	O
faster	O
than	O
competitors	O
.	O
</s>
<s>
This	O
means	O
that	O
many	O
in-house	O
blockchain	B-Application
solutions	O
will	O
be	O
nothing	O
more	O
than	O
cumbersome	O
databases.	O
"	O
</s>
<s>
The	O
analysis	O
of	O
public	O
blockchains	B-Application
has	O
become	O
increasingly	O
important	O
with	O
the	O
popularity	O
of	O
bitcoin	B-General_Concept
,	O
Ethereum	B-Application
,	O
litecoin	B-Protocol
and	O
other	O
cryptocurrencies	O
.	O
</s>
<s>
A	O
blockchain	B-Application
,	O
if	O
it	O
is	O
public	O
,	O
provides	O
anyone	O
who	O
wants	O
access	O
to	O
observe	O
and	O
analyse	O
the	O
chain	O
data	O
,	O
given	O
one	O
has	O
the	O
know-how	O
.	O
</s>
<s>
The	O
reason	O
for	O
this	O
is	O
accusations	O
of	O
blockchain-enabled	O
cryptocurrencies	O
enabling	O
illicit	O
dark	O
market	O
trade	O
of	O
drugs	O
,	O
weapons	O
,	O
money	O
laundering	O
,	O
etc	O
.	O
</s>
<s>
This	O
is	O
changing	O
and	O
now	O
specialised	O
tech	O
companies	O
provide	O
blockchain	B-Application
tracking	O
services	O
,	O
making	O
crypto	O
exchanges	O
,	O
law-enforcement	O
and	O
banks	O
more	O
aware	O
of	O
what	O
is	O
happening	O
with	O
crypto	O
funds	O
and	O
fiat-crypto	O
exchanges	O
.	O
</s>
<s>
The	O
development	O
,	O
some	O
argue	O
,	O
has	O
led	O
criminals	O
to	O
prioritise	O
the	O
use	O
of	O
new	O
cryptos	O
such	O
as	O
Monero	B-Protocol
.	O
</s>
<s>
The	O
question	O
is	O
about	O
the	O
public	O
accessibility	O
of	O
blockchain	B-Application
data	O
and	O
the	O
personal	O
privacy	O
of	O
the	O
very	O
same	O
data	O
.	O
</s>
<s>
It	O
is	O
a	O
key	O
debate	O
in	O
cryptocurrency	O
and	O
ultimately	O
in	O
the	O
blockchain	B-Application
.	O
</s>
<s>
In	O
April	O
2016	O
,	O
Standards	O
Australia	O
submitted	O
a	O
proposal	O
to	O
the	O
International	O
Organization	O
for	O
Standardization	O
to	O
consider	O
developing	O
standards	O
to	O
support	O
blockchain	B-Application
technology	I-Application
.	O
</s>
<s>
This	O
proposal	O
resulted	O
in	O
the	O
creation	O
of	O
ISO	O
Technical	O
Committee	O
307	O
,	O
Blockchain	B-Application
and	O
Distributed	B-Architecture
Ledger	B-Language
Technologies	O
.	O
</s>
<s>
The	O
technical	O
committee	O
has	O
working	O
groups	O
relating	O
to	O
blockchain	B-Application
terminology	O
,	O
reference	O
architecture	O
,	O
security	O
and	O
privacy	O
,	O
identity	O
,	O
smart	B-Application
contracts	I-Application
,	O
governance	O
and	O
interoperability	O
for	O
blockchain	B-Application
and	O
DLT	O
,	O
as	O
well	O
as	O
standards	O
specific	O
to	O
industry	O
sectors	O
and	O
generic	O
government	O
requirements	O
.	O
</s>
<s>
More	O
than	O
50	O
countries	O
are	O
participating	O
in	O
the	O
standardization	O
process	O
together	O
with	O
external	O
liaisons	O
such	O
as	O
the	O
Society	B-Protocol
for	I-Protocol
Worldwide	I-Protocol
Interbank	I-Protocol
Financial	I-Protocol
Telecommunication	I-Protocol
(	O
SWIFT	B-Protocol
)	O
,	O
the	O
European	O
Commission	O
,	O
the	O
International	O
Federation	O
of	O
Surveyors	O
,	O
the	O
International	O
Telecommunication	O
Union	O
(	O
ITU	O
)	O
and	O
the	O
United	O
Nations	O
Economic	O
Commission	O
for	O
Europe	O
(	O
UNECE	O
)	O
.	O
</s>
<s>
Many	O
other	O
national	O
standards	O
bodies	O
and	O
open	O
standards	O
bodies	O
are	O
also	O
working	O
on	O
blockchain	B-Application
standards	O
.	O
</s>
<s>
Although	O
most	O
of	O
blockchain	B-Application
implementation	O
are	O
decentralized	B-Operating_System
and	O
distributed	B-Architecture
,	O
Oracle	B-General_Concept
launched	O
a	O
centralized	O
blockchain	B-Application
table	O
feature	O
in	O
Oracle	B-General_Concept
21c	I-General_Concept
database	I-General_Concept
.	O
</s>
<s>
The	O
Blockchain	B-Application
Table	O
in	O
Oracle	B-General_Concept
21c	I-General_Concept
database	I-General_Concept
is	O
a	O
centralized	O
blockchain	B-Application
which	O
provide	O
immutable	O
feature	O
.	O
</s>
<s>
Compared	O
to	O
decentralized	B-Operating_System
blockchains	B-Application
,	O
centralized	O
blockchains	B-Application
normally	O
can	O
provide	O
a	O
higher	O
throughput	O
and	O
lower	O
latency	O
of	O
transactions	B-General_Concept
than	O
consensus-based	O
distributed	B-Architecture
blockchains	B-Application
.	O
</s>
<s>
Currently	O
,	O
there	O
are	O
at	O
least	O
four	O
types	O
of	O
blockchain	B-Application
networks	O
—	O
public	O
blockchains	B-Application
,	O
private	O
blockchains	B-Application
,	O
consortium	B-Application
blockchains	B-Application
and	O
hybrid	O
blockchains	B-Application
.	O
</s>
<s>
A	O
public	O
blockchain	B-Application
has	O
absolutely	O
no	O
access	O
restrictions	O
.	O
</s>
<s>
Anyone	O
with	O
an	O
Internet	O
connection	O
can	O
send	O
transactions	B-General_Concept
to	O
it	O
as	O
well	O
as	O
become	O
a	O
validator	O
(	O
i.e.	O
,	O
participate	O
in	O
the	O
execution	O
of	O
a	O
consensus	B-Operating_System
protocol	I-Operating_System
)	O
.	O
</s>
<s>
Usually	O
,	O
such	O
networks	O
offer	O
economic	O
incentives	O
for	O
those	O
who	O
secure	O
them	O
and	O
utilize	O
some	O
type	O
of	O
a	O
proof-of-stake	B-Protocol
or	O
proof-of-work	O
algorithm	O
.	O
</s>
<s>
Some	O
of	O
the	O
largest	O
,	O
most	O
known	O
public	O
blockchains	B-Application
are	O
the	O
bitcoin	B-General_Concept
blockchain	B-Application
and	O
the	O
Ethereum	B-Application
blockchain	B-Application
.	O
</s>
<s>
A	O
private	O
blockchain	B-Application
is	O
permissioned	O
.	O
</s>
<s>
Participant	O
and	O
validator	O
access	O
is	O
restricted	B-Application
.	O
</s>
<s>
To	O
distinguish	O
between	O
open	O
blockchains	B-Application
and	O
other	O
peer-to-peer	O
decentralized	B-Operating_System
database	O
applications	O
that	O
are	O
not	O
open	O
ad-hoc	O
compute	O
clusters	O
,	O
the	O
terminology	O
Distributed	B-Architecture
Ledger	B-Language
(	O
DLT	O
)	O
is	O
normally	O
used	O
for	O
private	O
blockchains	B-Application
.	O
</s>
<s>
A	O
hybrid	O
blockchain	B-Application
has	O
a	O
combination	O
of	O
centralized	O
and	O
decentralized	B-Operating_System
features	O
.	O
</s>
<s>
A	O
sidechain	O
is	O
a	O
designation	O
for	O
a	O
blockchain	B-Application
ledger	B-Language
that	O
runs	O
in	O
parallel	B-Operating_System
to	O
a	O
primary	O
blockchain	B-Application
.	O
</s>
<s>
Entries	O
from	O
the	O
primary	O
blockchain	B-Application
(	O
where	O
said	O
entries	O
typically	O
represent	O
digital	O
assets	O
)	O
can	O
be	O
linked	O
to	O
and	O
from	O
the	O
sidechain	O
;	O
this	O
allows	O
the	O
sidechain	O
to	O
otherwise	O
operate	O
independently	O
of	O
the	O
primary	O
blockchain	B-Application
(	O
e.g.	O
,	O
by	O
using	O
an	O
alternate	O
means	O
of	O
record	O
keeping	O
,	O
alternate	O
consensus	B-Operating_System
algorithm	I-Operating_System
,	O
etc	O
.	O
</s>
<s>
A	O
consortium	B-Application
blockchain	B-Application
is	O
a	O
type	O
of	O
blockchain	B-Application
that	O
combines	O
elements	O
of	O
both	O
public	O
and	O
private	O
blockchains	B-Application
.	O
</s>
<s>
In	O
a	O
consortium	B-Application
blockchain	B-Application
,	O
a	O
group	O
of	O
organizations	O
come	O
together	O
to	O
create	O
and	O
operate	O
the	O
blockchain	B-Application
,	O
rather	O
than	O
a	O
single	O
entity	O
.	O
</s>
<s>
The	O
consortium	B-Application
members	O
jointly	O
manage	O
the	O
blockchain	B-Application
network	O
and	O
are	O
responsible	O
for	O
validating	O
transactions	B-General_Concept
.	O
</s>
<s>
Consortium	B-Application
blockchains	B-Application
are	O
permissioned	O
,	O
meaning	O
that	O
only	O
certain	O
individuals	O
or	O
organizations	O
are	O
allowed	O
to	O
participate	O
in	O
the	O
network	O
.	O
</s>
<s>
This	O
allows	O
for	O
greater	O
control	O
over	O
who	O
can	O
access	O
the	O
blockchain	B-Application
and	O
helps	O
to	O
ensure	O
that	O
sensitive	O
information	O
is	O
kept	O
confidential	O
.	O
</s>
<s>
Consortium	B-Application
blockchains	B-Application
are	O
commonly	O
used	O
in	O
industries	O
where	O
multiple	O
organizations	O
need	O
to	O
collaborate	O
on	O
a	O
common	O
goal	O
,	O
such	O
as	O
supply	O
chain	O
management	O
or	O
financial	O
services	O
.	O
</s>
<s>
One	O
advantage	O
of	O
consortium	B-Application
blockchains	B-Application
is	O
that	O
they	O
can	O
be	O
more	O
efficient	O
and	O
scalable	O
than	O
public	O
blockchains	B-Application
,	O
as	O
the	O
number	O
of	O
nodes	O
required	O
to	O
validate	O
transactions	B-General_Concept
is	O
typically	O
smaller	O
.	O
</s>
<s>
Additionally	O
,	O
consortium	B-Application
blockchains	B-Application
can	O
provide	O
greater	O
security	O
and	O
reliability	O
than	O
private	O
blockchains	B-Application
,	O
as	O
the	O
consortium	B-Application
members	O
work	O
together	O
to	O
maintain	O
the	O
network	O
.	O
</s>
<s>
Some	O
examples	O
of	O
consortium	B-Application
blockchains	B-Application
include	O
Quorum	B-General_Concept
and	O
Hyperledger	B-Application
.	O
</s>
<s>
Blockchain	B-Application
technology	I-Application
can	O
be	O
integrated	O
into	O
multiple	O
areas	O
.	O
</s>
<s>
The	O
primary	O
use	O
of	O
blockchains	B-Application
is	O
as	O
a	O
distributed	B-Architecture
ledger	B-Language
for	O
cryptocurrencies	O
such	O
as	O
bitcoin	B-General_Concept
;	O
there	O
were	O
also	O
a	O
few	O
other	O
operational	O
products	O
that	O
had	O
matured	O
from	O
proof	O
of	O
concept	O
by	O
late	O
2016	O
.	O
</s>
<s>
As	O
of	O
2016	O
,	O
some	O
businesses	O
have	O
been	O
testing	O
the	O
technology	O
and	O
conducting	O
low-level	O
implementation	O
to	O
gauge	O
blockchain	B-Application
's	O
effects	O
on	O
organizational	O
efficiency	O
in	O
their	O
back	O
office	O
.	O
</s>
<s>
In	O
2019	O
,	O
it	O
was	O
estimated	O
that	O
around	O
$2.9	O
billion	O
were	O
invested	O
in	O
blockchain	B-Application
technology	I-Application
,	O
which	O
represents	O
an	O
89%	O
increase	O
from	O
the	O
year	O
prior	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
International	O
Data	O
Corp	O
has	O
estimated	O
that	O
corporate	O
investment	O
into	O
blockchain	B-Application
technology	I-Application
will	O
reach	O
$12.4	O
billion	O
by	O
2022	O
.	O
</s>
<s>
Furthermore	O
,	O
According	O
to	O
PricewaterhouseCoopers	O
(	O
PwC	O
)	O
,	O
the	O
second-largest	O
professional	O
services	O
network	O
in	O
the	O
world	O
,	O
blockchain	B-Application
technology	I-Application
has	O
the	O
potential	O
to	O
generate	O
an	O
annual	O
business	O
value	O
of	O
more	O
than	O
$3	O
trillion	O
by	O
2030	O
.	O
</s>
<s>
PwC	O
's	O
estimate	O
is	O
further	O
augmented	O
by	O
a	O
2018	O
study	O
that	O
they	O
have	O
conducted	O
,	O
in	O
which	O
PwC	O
surveyed	O
600	O
business	O
executives	O
and	O
determined	O
that	O
84%	O
have	O
at	O
least	O
some	O
exposure	O
to	O
utilizing	O
blockchain	B-Application
technology	I-Application
,	O
which	O
indicates	O
a	O
significant	O
demand	O
and	O
interest	O
in	O
blockchain	B-Application
technology	I-Application
.	O
</s>
<s>
In	O
2019	O
the	O
BBC	O
World	O
Service	O
radio	O
and	O
podcast	O
series	O
Fifty	O
Things	O
That	O
Made	O
the	O
Modern	O
Economy	O
identified	O
blockchain	B-Application
as	O
a	O
technology	O
that	O
would	O
have	O
far-reaching	O
consequences	O
for	O
economics	O
and	O
society	O
.	O
</s>
<s>
First	O
broadcast	B-Operating_System
29	O
June	O
2019	O
.	O
</s>
<s>
The	O
number	O
of	O
blockchain	B-Application
wallets	O
quadrupled	O
to	O
40	O
million	O
between	O
2016	O
and	O
2020	O
.	O
</s>
<s>
Most	O
cryptocurrencies	O
use	O
blockchain	B-Application
technology	I-Application
to	O
record	O
transactions	B-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
the	O
bitcoin	B-General_Concept
network	I-General_Concept
and	O
Ethereum	B-Application
network	O
are	O
both	O
based	O
on	O
blockchain	B-Application
.	O
</s>
<s>
The	O
criminal	O
enterprise	O
Silk	O
Road	O
,	O
which	O
operated	O
on	O
Tor	B-Application
,	O
utilized	O
cryptocurrency	O
for	O
payments	O
,	O
some	O
of	O
which	O
the	O
US	O
federal	O
government	O
has	O
seized	O
through	O
research	O
on	O
the	O
blockchain	B-Application
and	O
forfeiture	O
.	O
</s>
<s>
Governments	B-Architecture
have	I-Architecture
mixed	I-Architecture
policies	I-Architecture
on	O
the	O
legality	O
of	O
their	O
citizens	O
or	O
banks	O
owning	O
cryptocurrencies	O
.	O
</s>
<s>
China	O
implements	O
blockchain	B-Application
technology	I-Application
in	O
several	O
industries	O
including	O
a	O
national	O
digital	O
currency	O
which	O
launched	O
in	O
2020	O
.	O
</s>
<s>
Blockchain-based	O
smart	B-Application
contracts	I-Application
are	O
proposed	O
contracts	O
that	O
can	O
be	O
partially	O
or	O
fully	O
executed	O
or	O
enforced	O
without	O
human	O
interaction	O
.	O
</s>
<s>
One	O
of	O
the	O
main	O
objectives	O
of	O
a	O
smart	B-Application
contract	I-Application
is	O
automated	B-Application
escrow	O
.	O
</s>
<s>
A	O
key	O
feature	O
of	O
smart	B-Application
contracts	I-Application
is	O
that	O
they	O
do	O
not	O
need	O
a	O
trusted	O
third	O
party	O
(	O
such	O
as	O
a	O
trustee	O
)	O
to	O
act	O
as	O
an	O
intermediary	O
between	O
contracting	O
entities	O
—	O
the	O
blockchain	B-Application
network	O
executes	O
the	O
contract	O
on	O
its	O
own	O
.	O
</s>
<s>
This	O
may	O
reduce	O
friction	O
between	O
entities	O
when	O
transferring	O
value	O
and	O
could	O
subsequently	O
open	O
the	O
door	O
to	O
a	O
higher	O
level	O
of	O
transaction	O
automation	B-Application
.	O
</s>
<s>
An	O
IMF	O
staff	O
discussion	O
from	O
2018	O
reported	O
that	O
smart	B-Application
contracts	I-Application
based	O
on	O
blockchain	B-Application
technology	I-Application
might	O
reduce	O
moral	O
hazards	O
and	O
optimize	O
the	O
use	O
of	O
contracts	O
in	O
general	O
.	O
</s>
<s>
But	O
"	O
no	O
viable	O
smart	B-Application
contract	I-Application
systems	O
have	O
yet	O
emerged.	O
"	O
</s>
<s>
According	O
to	O
Reason	O
,	O
many	O
banks	O
have	O
expressed	O
interest	O
in	O
implementing	O
distributed	B-Architecture
ledgers	B-Language
for	O
use	O
in	O
banking	O
and	O
are	O
cooperating	O
with	O
companies	O
creating	O
private	O
blockchains	B-Application
,	O
and	O
according	O
to	O
a	O
September	O
2016	O
IBM	O
study	O
,	O
this	O
is	O
occurring	O
faster	O
than	O
expected	O
.	O
</s>
<s>
Moreover	O
,	O
as	O
the	O
blockchain	B-Application
industry	O
has	O
reached	O
early	O
maturity	O
institutional	O
appreciation	O
has	O
grown	O
that	O
it	O
is	O
,	O
practically	O
speaking	O
,	O
the	O
infrastructure	O
of	O
a	O
whole	O
new	O
financial	O
industry	O
,	O
with	O
all	O
the	O
implications	O
which	O
that	O
entails	O
.	O
</s>
<s>
Banks	O
such	O
as	O
UBS	O
are	O
opening	O
new	O
research	O
labs	O
dedicated	O
to	O
blockchain	B-Application
technology	I-Application
in	O
order	O
to	O
explore	O
how	O
blockchain	B-Application
can	O
be	O
used	O
in	O
financial	O
services	O
to	O
increase	O
efficiency	O
and	O
reduce	O
costs	O
.	O
</s>
<s>
Berenberg	O
,	O
a	O
German	O
bank	O
,	O
believes	O
that	O
blockchain	B-Application
is	O
an	O
"	O
overhyped	O
technology	O
"	O
that	O
has	O
had	O
a	O
large	O
number	O
of	O
"	O
proofs	O
of	O
concept	O
"	O
,	O
but	O
still	O
has	O
major	O
challenges	O
,	O
and	O
very	O
few	O
success	O
stories	O
.	O
</s>
<s>
The	O
blockchain	B-Application
has	O
also	O
given	O
rise	O
to	O
initial	B-Application
coin	I-Application
offerings	I-Application
(	O
ICOs	O
)	O
as	O
well	O
as	O
a	O
new	O
category	O
of	O
digital	O
asset	O
called	O
security	O
token	O
offerings	O
(	O
STOs	O
)	O
,	O
also	O
sometimes	O
referred	O
to	O
as	O
digital	O
security	O
offerings	O
(	O
DSOs	O
)	O
.	O
</s>
<s>
Blockchain	B-Application
technology	I-Application
,	O
such	O
as	O
cryptocurrencies	O
and	O
non-fungible	O
tokens	O
(	O
NFTs	O
)	O
,	O
has	O
been	O
used	O
in	O
video	O
games	O
for	O
monetization	O
.	O
</s>
<s>
Blockchain	B-Application
games	O
typically	O
allow	O
players	O
to	O
trade	O
these	O
in-game	O
items	O
for	O
cryptocurrency	O
,	O
which	O
can	O
then	O
be	O
exchanged	O
for	O
money	O
.	O
</s>
<s>
The	O
first	O
known	O
game	O
to	O
use	O
blockchain	B-Application
technologies	I-Application
was	O
CryptoKitties	B-Protocol
,	O
launched	O
in	O
November	O
2017	O
,	O
where	O
the	O
player	O
would	O
purchase	O
NFTs	O
with	O
Ethereum	B-Application
cryptocurrency	O
,	O
each	O
NFT	O
consisting	O
of	O
a	O
virtual	O
pet	O
that	O
the	O
player	O
could	O
breed	O
with	O
others	O
to	O
create	O
offspring	O
with	O
combined	O
traits	O
as	O
new	O
NFTs	O
.	O
</s>
<s>
CryptoKitties	B-Protocol
also	O
illustrated	O
scalability	O
problems	O
for	O
games	O
on	O
Ethereum	B-Application
when	O
it	O
created	O
significant	O
congestion	O
on	O
the	O
Ethereum	B-Application
network	O
in	O
early	O
2018	O
with	O
approximately	O
30%	O
of	O
all	O
Ethereum	B-Application
transactions	B-General_Concept
being	O
for	O
the	O
game	O
.	O
</s>
<s>
By	O
the	O
early	O
2020s	O
,	O
there	O
had	O
not	O
been	O
a	O
breakout	O
success	O
in	O
video	O
games	O
using	O
blockchain	B-Application
,	O
as	O
these	O
games	O
tend	O
to	O
focus	O
on	O
using	O
blockchain	B-Application
for	O
speculation	O
instead	O
of	O
more	O
traditional	O
forms	O
of	O
gameplay	O
,	O
which	O
offers	O
limited	O
appeal	O
to	O
most	O
players	O
.	O
</s>
<s>
However	O
,	O
limited	O
successes	O
of	O
some	O
games	O
,	O
such	O
as	O
Axie	B-Protocol
Infinity	I-Protocol
during	O
the	O
COVID-19	O
pandemic	O
,	O
and	O
corporate	O
plans	O
towards	O
metaverse	O
content	O
,	O
refueled	O
interest	O
in	O
the	O
area	O
of	O
GameFi	O
,	O
a	O
term	O
describing	O
the	O
intersection	O
of	O
video	O
games	O
and	O
financing	O
typically	O
backed	O
by	O
blockchain	B-Application
currency	O
,	O
in	O
the	O
second	O
half	O
of	O
2021	O
.	O
</s>
<s>
Several	O
major	O
publishers	O
,	O
including	O
Ubisoft	O
,	O
Electronic	O
Arts	O
,	O
and	O
Take	O
Two	O
Interactive	O
,	O
have	O
stated	O
that	O
blockchain	B-Application
and	O
NFT-based	O
games	O
are	O
under	O
serious	O
consideration	O
for	O
their	O
companies	O
in	O
the	O
future	O
.	O
</s>
<s>
In	O
October	O
2021	O
,	O
Valve	O
Corporation	O
banned	O
blockchain	B-Application
games	O
,	O
including	O
those	O
using	O
cryptocurrency	O
and	O
NFTs	O
,	O
from	O
being	O
hosted	O
on	O
its	O
Steam	B-Application
digital	O
storefront	O
service	O
,	O
which	O
is	O
widely	O
used	O
for	O
personal	O
computer	O
gaming	O
,	O
claiming	O
that	O
this	O
was	O
an	O
extension	O
of	O
their	O
policy	O
banning	O
games	O
that	O
offered	O
in-game	O
items	O
with	O
real-world	O
value	O
.	O
</s>
<s>
Valve	O
's	O
prior	O
history	O
with	O
gambling	O
,	O
specifically	O
skin	O
gambling	O
,	O
was	O
speculated	O
to	O
be	O
a	O
factor	O
in	O
the	O
decision	O
to	O
ban	O
blockchain	B-Application
games	O
.	O
</s>
<s>
Journalists	O
and	O
players	O
responded	O
positively	O
to	O
Valve	O
's	O
decision	O
as	O
blockchain	B-Application
and	O
NFT	O
games	O
have	O
a	O
reputation	O
for	O
scams	O
and	O
fraud	O
among	O
most	O
PC	O
gamers	O
,	O
Epic	O
Games	O
,	O
which	O
runs	O
the	O
Epic	O
Games	O
Store	O
in	O
competition	O
to	O
Steam	B-Application
,	O
said	O
that	O
they	O
would	O
be	O
open	O
to	O
accepted	O
blockchain	B-Application
games	O
in	O
the	O
wake	O
of	O
Valve	O
's	O
refusal	O
.	O
</s>
<s>
There	O
have	O
been	O
several	O
different	O
efforts	O
to	O
employ	O
blockchains	B-Application
in	O
supply	O
chain	O
management	O
.	O
</s>
<s>
Precious	O
commodities	O
mining	O
—	O
Blockchain	B-Application
technology	I-Application
has	O
been	O
used	O
for	O
tracking	O
the	O
origins	O
of	O
gemstones	O
and	O
other	O
precious	O
commodities	O
.	O
</s>
<s>
In	O
2016	O
,	O
The	O
Wall	O
Street	O
Journal	O
reported	O
that	O
the	O
blockchain	B-Application
technology	I-Application
company	O
Everledger	O
was	O
partnering	O
with	O
IBM	O
's	O
blockchain-based	O
tracking	O
service	O
to	O
trace	O
the	O
origin	O
of	O
diamonds	O
to	O
ensure	O
that	O
they	O
were	O
ethically	O
mined	O
.	O
</s>
<s>
Food	O
supply	O
—	O
As	O
of	O
2018	O
,	O
Walmart	O
and	O
IBM	O
were	O
running	O
a	O
trial	O
to	O
use	O
a	O
blockchain-backed	O
system	O
for	O
supply	O
chain	O
monitoring	O
for	O
lettuce	O
and	O
spinach	O
—	O
all	O
nodes	O
of	O
the	O
blockchain	B-Application
were	O
administered	O
by	O
Walmart	O
and	O
were	O
located	O
on	O
the	O
IBM	O
cloud	B-Architecture
.	O
</s>
<s>
Blockchain	B-Application
makes	O
up	O
for	O
this	O
shortcoming	O
and	O
makes	O
information	O
transparent	O
,	O
solving	O
the	O
difficulty	O
of	O
sustainable	O
development	O
of	O
the	O
industry	O
.	O
</s>
<s>
There	O
are	O
several	O
different	O
efforts	O
to	O
offer	O
domain	O
name	O
services	O
via	O
the	O
blockchain	B-Application
.	O
</s>
<s>
These	O
domain	O
names	O
can	O
be	O
controlled	O
by	O
the	O
use	O
of	O
a	O
private	B-Application
key	I-Application
,	O
which	O
purports	O
to	O
allow	O
for	O
uncensorable	O
websites	O
.	O
</s>
<s>
Namecoin	B-Protocol
is	O
a	O
cryptocurrency	O
that	O
supports	O
the	O
"	O
.bit	B-Protocol
"	O
top-level	O
domain	O
(	O
TLD	O
)	O
.	O
</s>
<s>
Namecoin	B-Protocol
was	O
forked	O
from	O
bitcoin	B-General_Concept
in	O
2011	O
.	O
</s>
<s>
The	O
.bit	B-Protocol
TLD	O
is	O
not	O
sanctioned	O
by	O
ICANN	B-Application
,	O
instead	O
requiring	O
an	O
alternative	B-Protocol
DNS	I-Protocol
root	I-Protocol
.	O
</s>
<s>
As	O
of	O
2015	O
,	O
.bit	B-Protocol
was	O
used	O
by	O
28	O
websites	O
,	O
out	O
of	O
120,000	O
registered	O
names	O
.	O
</s>
<s>
Namecoin	B-Protocol
was	O
dropped	O
by	O
OpenNIC	B-Protocol
in	O
2019	O
,	O
due	O
to	O
malware	O
and	O
potential	O
other	O
legal	O
issues	O
.	O
</s>
<s>
Other	O
blockchain	B-Application
alternatives	B-Application
to	I-Application
ICANN	I-Application
include	O
The	O
Handshake	O
Network	O
,	O
EmerDNS	O
,	O
and	O
Unstoppable	O
Domains	O
.	O
</s>
<s>
Specific	O
TLDs	O
include	O
"	O
.eth	O
"	O
,	O
"	O
.luxe	O
"	O
,	O
and	O
"	O
.kred	O
"	O
,	O
which	O
are	O
associated	O
with	O
the	O
Ethereum	B-Application
blockchain	B-Application
through	O
the	O
Ethereum	B-Application
Name	O
Service	O
(	O
ENS	O
)	O
.	O
</s>
<s>
The	O
.kred	O
TLD	O
also	O
acts	O
as	O
an	O
alternative	O
to	O
conventional	O
cryptocurrency	B-Protocol
wallet	I-Protocol
addresses	O
as	O
a	O
convenience	O
for	O
transferring	O
cryptocurrency	O
.	O
</s>
<s>
Blockchain	B-Application
technology	I-Application
can	O
be	O
used	O
to	O
create	O
a	O
permanent	O
,	O
public	O
,	O
transparent	O
ledger	B-Language
system	O
for	O
compiling	O
data	O
on	O
sales	O
,	O
tracking	O
digital	O
use	O
and	O
payments	O
to	O
content	O
creators	O
,	O
such	O
as	O
wireless	O
users	O
or	O
musicians	O
.	O
</s>
<s>
The	O
Gartner	O
2019	O
CIO	O
Survey	O
reported	O
2%	O
of	O
higher	O
education	O
respondents	O
had	O
launched	O
blockchain	B-Application
projects	O
and	O
another	O
18%	O
were	O
planning	O
academic	O
projects	O
in	O
the	O
next	O
24	O
months	O
.	O
</s>
<s>
In	O
2017	O
,	O
IBM	O
partnered	O
with	O
ASCAP	O
and	O
PRS	O
for	O
Music	O
to	O
adopt	O
blockchain	B-Application
technology	I-Application
in	O
music	O
distribution	O
.	O
</s>
<s>
Imogen	O
Heap	O
's	O
Mycelia	O
service	O
has	O
also	O
been	O
proposed	O
as	O
a	O
blockchain-based	O
alternative	O
"	O
that	O
gives	O
artists	O
more	O
control	O
over	O
how	O
their	O
songs	O
and	O
associated	O
data	O
circulate	O
among	O
fans	O
and	O
other	O
musicians.	O
"	O
</s>
<s>
New	O
distribution	O
methods	O
are	O
available	O
for	O
the	O
insurance	O
industry	O
such	O
as	O
peer-to-peer	O
insurance	O
,	O
parametric	O
insurance	O
and	O
microinsurance	O
following	O
the	O
adoption	O
of	O
blockchain	B-Application
.	O
</s>
<s>
The	O
sharing	O
economy	O
and	O
IoT	B-Operating_System
are	O
also	O
set	O
to	O
benefit	O
from	O
blockchains	B-Application
because	O
they	O
involve	O
many	O
collaborating	O
peers	O
.	O
</s>
<s>
The	O
use	O
of	O
blockchain	B-Application
in	O
libraries	O
is	O
being	O
studied	O
with	O
a	O
grant	O
from	O
the	O
U.S.	O
Institute	O
of	O
Museum	O
and	O
Library	O
Services	O
.	O
</s>
<s>
Other	O
blockchain	B-Application
designs	O
include	O
Hyperledger	B-Application
,	O
a	O
collaborative	O
effort	O
from	O
the	B-Operating_System
Linux	I-Operating_System
Foundation	I-Operating_System
to	O
support	O
blockchain-based	O
distributed	B-Architecture
ledgers	B-Language
,	O
with	O
projects	O
under	O
this	O
initiative	O
including	O
Hyperledger	B-Application
Burrow	O
(	O
by	O
Monax	O
)	O
and	O
Hyperledger	B-Application
Fabric	O
(	O
spearheaded	O
by	O
IBM	O
)	O
.	O
</s>
<s>
Another	O
is	O
Quorum	B-General_Concept
,	O
a	O
permissioned	O
private	O
blockchain	B-Application
by	O
JPMorgan	O
Chase	O
with	O
private	O
storage	O
,	O
used	O
for	O
contract	O
applications	O
.	O
</s>
<s>
Oracle	B-General_Concept
introduced	O
a	O
blockchain	B-Application
table	O
feature	O
in	O
its	O
Oracle	B-General_Concept
21c	I-General_Concept
database	I-General_Concept
.	O
</s>
<s>
Blockchain	B-Application
is	O
also	O
being	O
used	O
in	O
peer-to-peer	O
energy	O
trading	O
.	O
</s>
<s>
Blockchain	B-Application
could	O
be	O
used	O
in	O
detecting	O
counterfeits	O
by	O
associating	O
unique	O
identifiers	O
to	O
products	O
,	O
documents	O
and	O
shipments	O
,	O
and	O
storing	O
records	O
associated	O
with	O
transactions	B-General_Concept
that	O
cannot	O
be	O
forged	O
or	O
altered	O
.	O
</s>
<s>
It	O
is	O
however	O
argued	O
that	O
blockchain	B-Application
technology	I-Application
needs	O
to	O
be	O
supplemented	O
with	O
technologies	O
that	O
provide	O
a	O
strong	O
binding	O
between	O
physical	O
objects	O
and	O
blockchain	B-Application
systems	O
.	O
</s>
<s>
The	O
Dutch	O
Standardisation	O
organisation	O
NEN	O
uses	O
blockchain	B-Application
together	O
with	O
QR	O
Codes	O
to	O
authenticate	O
certificates	O
.	O
</s>
<s>
2022	O
Jan	O
30	O
Beijing	O
and	O
Shanghai	O
are	O
among	O
the	O
cities	O
designated	O
by	O
China	O
to	O
trial	O
blockchain	B-Application
applications	O
.	O
</s>
<s>
With	O
the	O
increasing	O
number	O
of	O
blockchain	B-Application
systems	O
appearing	O
,	O
even	O
only	O
those	O
that	O
support	O
cryptocurrencies	O
,	O
blockchain	B-Application
interoperability	O
is	O
becoming	O
a	O
topic	O
of	O
major	O
importance	O
.	O
</s>
<s>
The	O
objective	O
is	O
to	O
support	O
transferring	O
assets	O
from	O
one	O
blockchain	B-Application
system	O
to	O
another	O
blockchain	B-Application
system	O
.	O
</s>
<s>
The	O
objective	O
of	O
blockchain	B-Application
interoperability	O
is	O
therefore	O
to	O
support	O
such	O
cooperation	O
among	O
blockchain	B-Application
systems	O
,	O
despite	O
those	O
kinds	O
of	O
differences	O
.	O
</s>
<s>
There	O
are	O
already	O
several	O
blockchain	B-Application
interoperability	O
solutions	O
available	O
.	O
</s>
<s>
They	O
can	O
be	O
classified	O
into	O
three	O
categories	O
:	O
cryptocurrency	O
interoperability	O
approaches	O
,	O
blockchain	B-Application
engines	O
,	O
and	O
blockchain	B-Application
connectors	O
.	O
</s>
<s>
Several	O
individual	O
IETF	O
participants	O
produced	O
the	O
draft	O
of	O
a	O
blockchain	B-Application
interoperability	O
architecture	O
.	O
</s>
<s>
Some	O
cryptocurrencies	O
use	O
blockchain	B-Application
mining	O
—	O
the	O
peer-to-peer	O
computer	O
computations	O
by	O
which	O
transactions	B-General_Concept
are	O
validated	O
and	O
verified	O
.	O
</s>
<s>
In	O
June	O
2018	O
,	O
the	O
Bank	O
for	O
International	O
Settlements	O
criticized	O
the	O
use	O
of	O
public	O
proof-of-work	O
blockchains	B-Application
for	O
their	O
high	O
energy	O
consumption	O
.	O
</s>
<s>
Early	O
concern	O
over	O
the	O
high	O
energy	O
consumption	O
was	O
a	O
factor	O
in	O
later	O
blockchains	B-Application
such	O
as	O
Cardano	B-Protocol
(	O
2017	O
)	O
,	O
Solana	B-Protocol
(	O
2020	O
)	O
and	O
Polkadot	B-Protocol
(	O
2020	O
)	O
adopting	O
the	O
less	O
energy-intensive	O
proof-of-stake	B-Protocol
model	O
.	O
</s>
<s>
Researchers	O
have	O
estimated	O
that	O
Bitcoin	B-General_Concept
consumes	O
100,000	O
times	O
as	O
much	O
energy	O
as	O
proof-of-stake	B-Protocol
networks	O
.	O
</s>
<s>
In	O
2021	O
,	O
a	O
study	O
by	O
Cambridge	O
University	O
determined	O
that	O
Bitcoin	B-General_Concept
(	O
at	O
121	O
terawatt-hours	O
per	O
year	O
)	O
used	O
more	O
electricity	O
than	O
Argentina	O
(	O
at	O
121TWh	O
)	O
and	O
the	O
Netherlands	O
(	O
109TWh	O
)	O
.	O
</s>
<s>
According	O
to	O
Digiconomist	O
,	O
one	O
bitcoin	B-General_Concept
transaction	O
required	O
708	O
kilowatt-hours	O
of	O
electrical	O
energy	O
,	O
the	O
amount	O
an	O
average	O
U.S.	O
household	O
consumed	O
in	O
24	O
days	O
.	O
</s>
<s>
In	O
February	O
2021	O
,	O
U.S.	O
Treasury	O
secretary	O
Janet	O
Yellen	O
called	O
Bitcoin	B-General_Concept
"	O
an	O
extremely	O
inefficient	O
way	O
to	O
conduct	O
transactions	B-General_Concept
"	O
,	O
saying	O
"	O
the	O
amount	O
of	O
energy	O
consumed	O
in	O
processing	O
those	O
transactions	B-General_Concept
is	O
staggering	O
"	O
.	O
</s>
<s>
In	O
March	O
2021	O
,	O
Bill	O
Gates	O
stated	O
that	O
"	O
Bitcoin	B-General_Concept
uses	O
more	O
electricity	O
per	O
transaction	O
than	O
any	O
other	O
method	O
known	O
to	O
mankind	O
"	O
,	O
adding	O
"	O
It	O
's	O
not	O
a	O
great	O
climate	O
thing.	O
"	O
</s>
<s>
Nicholas	O
Weaver	O
,	O
of	O
the	O
International	O
Computer	B-General_Concept
Science	I-General_Concept
Institute	O
at	O
the	O
University	O
of	O
California	O
,	O
Berkeley	O
,	O
examined	O
blockchain	B-Application
's	O
online	O
security	O
,	O
and	O
the	O
energy	O
efficiency	O
of	O
proof-of-work	O
public	O
blockchains	B-Application
,	O
and	O
in	O
both	O
cases	O
found	O
it	O
grossly	O
inadequate	O
.	O
</s>
<s>
The	O
31TWh-45TWh	O
of	O
electricity	O
used	O
for	O
bitcoin	B-General_Concept
in	O
2018	O
produced	O
17-23	O
million	O
tonnes	O
of	O
.	O
</s>
<s>
By	O
2022	O
,	O
the	O
University	O
of	O
Cambridge	O
and	O
Digiconomist	O
estimated	O
that	O
the	O
two	O
largest	O
proof-of-work	O
blockchains	B-Application
,	O
Bitcoin	B-General_Concept
and	O
Ethereum	B-Application
,	O
together	O
used	O
twice	O
as	O
much	O
electricity	O
in	O
one	O
year	O
as	O
the	O
whole	O
of	O
Sweden	O
,	O
leading	O
to	O
the	O
release	O
of	O
up	O
to	O
120	O
million	O
tonnes	O
of	O
each	O
year	O
.	O
</s>
<s>
Some	O
cryptocurrency	O
developers	O
are	O
considering	O
moving	O
from	O
the	O
proof-of-work	O
model	O
to	O
the	O
proof-of-stake	B-Protocol
model	O
.	O
</s>
<s>
In	O
October	O
2014	O
,	O
the	O
MIT	O
Bitcoin	B-General_Concept
Club	O
,	O
with	O
funding	O
from	O
MIT	O
alumni	O
,	O
provided	O
undergraduate	O
students	O
at	O
the	O
Massachusetts	O
Institute	O
of	O
Technology	O
access	O
to	O
$100	O
of	O
bitcoin	B-General_Concept
.	O
</s>
<s>
Many	O
universities	O
have	O
founded	O
departments	O
focusing	O
on	O
crypto	O
and	O
blockchain	B-Application
,	O
including	O
MIT	O
,	O
in	O
2017	O
.	O
</s>
<s>
In	O
the	O
same	O
year	O
,	O
Edinburgh	O
became	O
"	O
one	O
of	O
the	O
first	O
big	O
European	O
universities	O
to	O
launch	O
a	O
blockchain	B-Application
course	O
"	O
,	O
according	O
to	O
the	O
Financial	O
Times	O
.	O
</s>
<s>
Motivations	O
for	O
adopting	O
blockchain	B-Application
technology	I-Application
(	O
an	O
aspect	O
of	O
innovation	O
adoptation	O
)	O
have	O
been	O
investigated	O
by	O
researchers	O
.	O
</s>
<s>
Scholars	O
in	O
business	O
and	O
management	O
have	O
started	O
studying	O
the	O
role	O
of	O
blockchains	B-Application
to	O
support	O
collaboration	O
.	O
</s>
<s>
It	O
has	O
been	O
argued	O
that	O
blockchains	B-Application
can	O
foster	O
both	O
cooperation	O
(	O
i.e.	O
,	O
prevention	O
of	O
opportunistic	O
behavior	O
)	O
and	O
coordination	O
(	O
i.e.	O
,	O
communication	O
and	O
information	O
sharing	O
)	O
.	O
</s>
<s>
Thanks	O
to	O
reliability	O
,	O
transparency	O
,	O
traceability	O
of	O
records	O
,	O
and	O
information	O
immutability	O
,	O
blockchains	B-Application
facilitate	O
collaboration	O
in	O
a	O
way	O
that	O
differs	O
both	O
from	O
the	O
traditional	O
use	O
of	O
contracts	O
and	O
from	O
relational	O
norms	O
.	O
</s>
<s>
Contrary	O
to	O
contracts	O
,	O
blockchains	B-Application
do	O
not	O
directly	O
rely	O
on	O
the	O
legal	O
system	O
to	O
enforce	O
agreements	O
.	O
</s>
<s>
In	O
addition	O
,	O
contrary	O
to	O
the	O
use	O
of	O
relational	O
norms	O
,	O
blockchains	B-Application
do	O
not	O
require	O
a	O
trust	O
or	O
direct	O
connections	O
between	O
collaborators	O
.	O
</s>
<s>
Blockchain	B-Application
adoption	O
requires	O
a	O
framework	O
to	O
identify	O
the	O
risk	O
of	O
exposure	O
associated	O
with	O
transactions	B-General_Concept
using	O
blockchain	B-Application
.	O
</s>
<s>
The	O
Internal	O
Audit	O
Foundation	O
study	O
,	O
Blockchain	B-Application
and	O
Internal	O
Audit	O
,	O
assesses	O
these	O
factors	O
.	O
</s>
<s>
The	O
American	O
Institute	O
of	O
Certified	O
Public	O
Accountants	O
has	O
outlined	O
new	O
roles	O
for	O
auditors	O
as	O
a	O
result	O
of	O
blockchain	B-Application
.	O
</s>
<s>
In	O
September	O
2015	O
,	O
the	O
first	O
peer-reviewed	O
academic	O
journal	O
dedicated	O
to	O
cryptocurrency	O
and	O
blockchain	B-Application
technology	I-Application
research	O
,	O
Ledger	B-Language
,	O
was	O
announced	O
.	O
</s>
<s>
The	O
journal	O
covers	O
aspects	O
of	O
mathematics	O
,	O
computer	B-General_Concept
science	I-General_Concept
,	O
engineering	O
,	O
law	O
,	O
economics	O
and	O
philosophy	O
that	O
relate	O
to	O
cryptocurrencies	O
.	O
</s>
<s>
The	O
journal	O
encourages	O
authors	O
to	O
digitally	O
sign	O
a	O
file	B-Error_Name
hash	I-Error_Name
of	O
submitted	O
papers	O
,	O
which	O
are	O
then	O
timestamped	O
into	O
the	O
bitcoin	B-General_Concept
blockchain	B-Application
.	O
</s>
<s>
Authors	O
are	O
also	O
asked	O
to	O
include	O
a	O
personal	O
bitcoin	B-General_Concept
address	O
on	O
the	O
first	O
page	O
of	O
their	O
papers	O
for	O
non-repudiation	O
purposes	O
.	O
</s>
