<s>
A	O
cryptocurrency	B-Protocol
wallet	I-Protocol
is	O
a	O
device	O
,	O
physical	O
medium	O
,	O
program	O
or	O
a	O
service	O
which	O
stores	O
the	O
public	B-Application
and/or	I-Application
private	I-Application
keys	I-Application
for	O
cryptocurrency	O
transactions	O
.	O
</s>
<s>
In	O
addition	O
to	O
this	O
basic	O
function	O
of	O
storing	O
the	O
keys	O
,	O
a	O
cryptocurrency	B-Protocol
wallet	I-Protocol
more	O
often	O
offers	O
the	O
functionality	O
of	O
encrypting	O
and/or	O
signing	O
information	O
.	O
</s>
<s>
Signing	O
can	O
for	O
example	O
result	O
in	O
executing	O
a	O
smart	B-Application
contract	I-Application
,	O
a	O
cryptocurrency	O
transaction	O
(	O
see	O
"	O
bitcoin	B-Protocol
transaction	O
"	O
image	O
)	O
,	O
identification	O
or	O
legally	O
signing	O
a	O
'	O
document	O
 '	O
(	O
see	O
"	O
application	O
form	O
"	O
image	O
)	O
.	O
</s>
<s>
In	O
2008	O
bitcoin	B-Protocol
was	O
introduced	O
as	O
the	O
first	O
cryptocurrency	O
following	O
the	O
principle	O
outlined	O
by	O
Satoshi	O
Nakamoto	O
in	O
the	O
paper	O
“	O
Bitcoin	B-Protocol
:	O
A	O
Peer-to-Peer	O
Electronic	O
Cash	O
System.	O
”	O
The	O
project	O
was	O
described	O
as	O
an	O
electronic	O
payment	O
system	O
using	O
cryptographic	O
proof	O
instead	O
of	O
trust	O
.	O
</s>
<s>
It	O
also	O
mentioned	O
using	O
cryptographic	O
proof	O
to	O
verify	O
and	O
record	O
transactions	O
on	O
a	O
blockchain	B-Application
.	O
</s>
<s>
A	O
cryptocurrency	B-Protocol
wallet	I-Protocol
works	O
by	O
a	O
theoretical	O
or	O
random	O
number	O
being	O
generated	O
and	O
used	O
with	O
a	O
length	O
that	O
depends	O
on	O
the	O
algorithm	O
size	O
of	O
the	O
cryptocurrency	O
's	O
technology	O
requirements	O
.	O
</s>
<s>
The	O
number	O
is	O
converted	O
to	O
a	O
private	B-Application
key	I-Application
using	O
the	O
specific	O
requirements	O
of	O
the	O
cryptocurrency	O
cryptography	O
algorithm	O
requirement	O
.	O
</s>
<s>
A	O
public	B-Application
key	I-Application
is	O
then	O
generated	O
from	O
the	O
private	B-Application
key	I-Application
using	O
whichever	O
cryptographic	O
algorithm	O
is	O
required	O
.	O
</s>
<s>
The	O
private	B-Application
key	I-Application
is	O
used	O
by	O
the	O
owner	O
to	O
access	O
and	O
send	O
cryptocurrency	O
and	O
is	O
private	O
to	O
the	O
owner	O
,	O
whereas	O
the	O
public	B-Application
key	I-Application
is	O
to	O
be	O
shared	O
to	O
any	O
third	O
party	O
to	O
receive	O
cryptocurrency	O
.	O
</s>
<s>
Up	O
to	O
this	O
stage	O
no	O
computer	O
or	O
electronic	O
device	O
is	O
required	O
and	O
all	O
key	B-Application
pairs	I-Application
can	O
be	O
mathematically	O
derived	O
and	O
written	O
down	O
by	O
hand	O
.	O
</s>
<s>
The	O
private	B-Application
key	I-Application
and	O
public	B-Application
key	I-Application
pair	I-Application
(	O
known	O
as	O
an	O
address	O
)	O
are	O
not	O
known	O
by	O
the	O
blockchain	B-Application
or	O
anyone	O
else	O
.	O
</s>
<s>
The	O
blockchain	B-Application
will	O
only	O
record	O
the	O
transaction	O
of	O
the	O
public	O
address	O
when	O
cryptocurrency	O
is	O
sent	O
to	O
it	O
,	O
thus	O
recording	O
in	O
the	O
blockchain	B-Application
ledger	O
the	O
transaction	O
of	O
the	O
public	O
address	O
.	O
</s>
<s>
Collision	O
(	O
two	O
or	O
more	O
wallets	O
having	O
the	O
same	O
private	B-Application
key	I-Application
)	O
is	O
theoretically	O
possible	O
,	O
since	O
keys	O
can	O
be	O
generated	O
without	O
being	O
used	O
for	O
transactions	O
,	O
and	O
are	O
therefore	O
offline	O
until	O
recorded	O
in	O
the	O
blockchain	B-Application
ledger	O
.	O
</s>
<s>
However	O
,	O
this	O
possibility	O
is	O
effectively	O
negated	O
because	O
the	O
theoretical	O
probability	O
of	O
two	O
or	O
more	O
private	B-Application
keys	I-Application
being	O
the	O
same	O
is	O
extremely	O
low	O
.	O
</s>
<s>
The	O
number	O
of	O
possible	O
wallets	O
and	O
thus	O
private	B-Application
keys	I-Application
is	O
extremely	O
high	O
,	O
so	O
duplicating	O
or	O
hacking	O
a	O
certain	O
key	O
would	O
be	O
inconceivable	O
.	O
</s>
<s>
In	O
modern	O
convention	O
a	O
seed	O
phrase	O
is	O
now	O
utilised	O
which	O
is	O
a	O
random	O
12	O
to	O
24	O
(	O
or	O
even	O
greater	O
)	O
list	O
of	O
dictionary	O
words	O
which	O
is	O
an	O
unencrypted	O
form	O
of	O
the	O
private	B-Application
key	I-Application
.	O
</s>
<s>
When	O
online	O
,	O
exchange	O
and	O
hardware	B-Protocol
wallets	I-Protocol
are	O
generated	O
using	O
random	O
numbers	O
,	O
and	O
the	O
user	O
is	O
asked	O
to	O
supply	O
a	O
seed	O
phrase	O
.	O
</s>
<s>
A	O
number	O
of	O
technologies	O
known	O
as	O
wallets	O
exist	O
that	O
store	O
the	O
key	O
value	O
pair	O
of	O
private	O
and	O
public	B-Application
key	I-Application
known	O
as	O
wallets	O
.	O
</s>
<s>
A	O
wallet	O
hosts	O
the	O
details	O
of	O
the	O
key	B-Application
pair	I-Application
making	O
cryptocurrency	O
transactions	O
possible	O
.	O
</s>
<s>
A	O
brainwallet	O
or	O
brain	O
wallet	O
is	O
a	O
type	O
of	O
wallet	O
in	O
which	O
one	O
memorizes	O
a	O
passcode	O
(	O
a	O
private	B-Application
key	I-Application
or	O
seed	O
phrase	O
)	O
.	O
</s>
<s>
Several	O
hundred	O
brainwallets	O
exist	O
on	O
the	O
Bitcoin	B-General_Concept
blockchain	I-General_Concept
,	O
but	O
most	O
of	O
them	O
have	O
been	O
drained	O
,	O
sometimes	O
repeatedly	O
.	O
</s>
<s>
DApp	B-Application
browsers	O
are	O
specialized	O
software	O
that	O
supports	O
decentralized	B-Application
applications	I-Application
.	O
</s>
<s>
DApp	B-Application
browsers	O
are	O
considered	O
to	O
be	O
the	O
browsers	O
of	O
Web3	O
and	O
are	O
the	O
gateway	O
to	O
access	O
the	O
decentralized	B-Application
applications	I-Application
which	O
are	O
based	O
on	O
blockchain	B-Application
technology	I-Application
.	O
</s>
<s>
That	O
means	O
all	O
DApp	B-Application
browsers	O
must	O
have	O
a	O
unique	O
code	O
system	O
to	O
unify	O
all	O
the	O
different	O
codes	O
of	O
the	O
DApps	B-Application
.	O
</s>
<s>
While	O
crypto	B-Protocol
wallets	I-Protocol
are	O
focused	O
on	O
the	O
exchange	O
,	O
purchase	O
,	O
sale	O
of	O
digital	O
assets	O
and	O
support	O
narrowly	O
targeted	O
applications	O
,	O
the	O
browsers	O
support	O
different	O
kinds	O
of	O
applications	O
of	O
various	O
formats	O
,	O
including	O
exchange	O
,	O
games	O
,	O
NFTs	O
marketplaces	O
,	O
etc	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
basic	O
function	O
of	O
storing	O
the	O
keys	O
,	O
a	O
cryptocurrency	B-Protocol
wallet	I-Protocol
may	O
also	O
have	O
one	O
or	O
more	O
of	O
the	O
following	O
characteristics	O
.	O
</s>
<s>
A	O
simple	O
cryptocurrency	B-Protocol
wallet	I-Protocol
contains	O
pairs	O
of	O
public	O
and	O
private	O
cryptographic	O
keys	O
.	O
</s>
<s>
A	O
public	B-Application
key	I-Application
allows	O
others	O
to	O
make	O
payments	O
to	O
the	O
address	O
derived	O
from	O
it	O
,	O
whereas	O
a	O
private	B-Application
key	I-Application
enables	O
the	O
spending	O
of	O
cryptocurrency	O
from	O
that	O
address	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
bitcoin	B-Protocol
and	O
cryptocurrencies	O
derived	O
from	O
it	O
,	O
the	O
cryptocurrency	O
is	O
decentrally	O
stored	O
and	O
maintained	O
in	O
a	O
publicly	O
available	O
distributed	O
ledger	O
called	O
the	O
blockchain	B-Application
.	O
</s>
<s>
The	O
European	O
Union	O
is	O
creating	O
an	O
eIDAS	O
compatible	O
European	O
Self-Sovereign	O
Identity	O
Framework	O
(	O
ESSIF	O
)	O
which	O
runs	O
on	O
the	O
European	O
Blockchain	B-Application
Services	O
Infrastructure	O
(	O
EBSI	O
)	O
.	O
</s>
<s>
In	O
contrast	O
to	O
simple	O
cryptocurrency	B-Protocol
wallets	I-Protocol
requiring	O
just	O
one	O
party	O
to	O
sign	O
a	O
transaction	O
,	O
multi-sig	O
wallets	O
require	O
multiple	O
parties	O
to	O
sign	O
a	O
transaction	O
.	O
</s>
<s>
In	O
the	O
cryptocurrency	O
space	O
,	O
smart	B-Application
contracts	I-Application
are	O
digitally	O
signed	O
in	O
the	O
same	O
way	O
a	O
cryptocurrency	O
transaction	O
is	O
signed	O
.	O
</s>
<s>
The	O
signing	O
keys	O
are	O
held	O
in	O
a	O
cryptocurrency	B-Protocol
wallet	I-Protocol
.	O
</s>
<s>
This	O
would	O
utilize	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
,	O
e.g.	O
</s>
<s>
SHA-256	B-Algorithm
(	O
seed	O
+	O
n	O
)	O
,	O
where	O
n	O
is	O
an	O
ASCII-coded	O
number	O
that	O
starts	O
from	O
1	O
and	O
increments	O
as	O
additional	O
keys	O
are	O
needed	O
.	O
</s>
<s>
As	O
a	O
deterministic	O
wallet	O
,	O
it	O
also	O
derives	O
keys	O
from	O
a	O
single	O
master	O
root	O
seed	O
,	O
but	O
instead	O
of	O
having	O
a	O
single	O
"	O
chain	O
"	O
of	O
keypairs	B-Application
,	O
an	O
HD	O
wallet	O
supports	O
multiple	O
key	B-Application
pair	I-Application
chains	O
.	O
</s>
<s>
This	O
allows	O
a	O
single	O
key	O
string	O
to	O
be	O
used	O
to	O
generate	O
an	O
entire	O
tree	O
of	O
key	B-Application
pairs	I-Application
with	O
a	O
stratified	O
structure	O
.	O
</s>
<s>
BIP39	O
proposed	O
the	O
use	O
of	O
a	O
set	O
of	O
human-readable	O
words	O
to	O
derive	O
the	O
master	O
private	B-Application
key	I-Application
of	O
a	O
wallet	O
.	O
</s>
<s>
Therefore	O
,	O
any	O
backups	O
of	O
the	O
wallet	O
must	O
store	O
each	O
and	O
every	O
single	O
private	B-Application
key	I-Application
used	O
as	O
an	O
address	O
,	O
as	O
well	O
as	O
a	O
buffer	O
of	O
100	O
or	O
so	O
future	O
keys	O
that	O
may	O
have	O
already	O
been	O
given	O
out	O
as	O
addresses	O
but	O
not	O
received	O
payments	O
yet	O
.	O
</s>
<s>
When	O
choosing	O
a	O
wallet	O
,	O
the	O
owner	O
must	O
keep	O
in	O
mind	O
who	O
is	O
supposed	O
to	O
have	O
access	O
to	O
(	O
a	O
copy	O
of	O
)	O
the	O
private	B-Application
keys	I-Application
and	O
thus	O
potentially	O
has	O
signing	O
capabilities	O
.	O
</s>
<s>
Gox	O
exchange	O
,	O
which	O
'	O
lost	O
 '	O
most	O
of	O
their	O
clients	O
 '	O
bitcoins	B-Protocol
.	O
</s>
<s>
Downloading	O
a	O
cryptocurrency	B-Protocol
wallet	I-Protocol
from	O
a	O
wallet	O
provider	O
to	O
a	O
computer	O
or	O
phone	O
does	O
not	O
automatically	O
mean	O
that	O
the	O
owner	O
is	O
the	O
only	O
one	O
who	O
has	O
a	O
copy	O
of	O
the	O
private	B-Application
keys	I-Application
.	O
</s>
<s>
In	O
extreme	O
cases	O
even	O
a	O
computer	O
which	O
is	O
not	B-Architecture
connected	I-Architecture
to	I-Architecture
any	I-Architecture
network	I-Architecture
can	O
be	O
hacked	O
.	O
</s>
