<s>
Streebog	B-Algorithm
(	O
)	O
is	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
defined	O
in	O
the	O
Russian	O
national	O
standard	O
GOST	B-Algorithm
R	I-Algorithm
34.11-2012	I-Algorithm
Information	O
Technology	O
–	O
Cryptographic	O
Information	O
Security	O
–	O
Hash	B-Algorithm
Function	I-Algorithm
.	O
</s>
<s>
It	O
was	O
created	O
to	O
replace	O
an	O
obsolete	O
GOST	B-Algorithm
hash	B-Algorithm
function	I-Algorithm
defined	O
in	O
the	O
old	O
standard	O
GOST	B-Algorithm
R	I-Algorithm
34.11-94	I-Algorithm
,	O
and	O
as	O
an	O
asymmetric	O
reply	O
to	O
SHA-3	B-Algorithm
competition	I-Algorithm
by	O
the	O
US	O
National	O
Institute	O
of	O
Standards	O
and	O
Technology	O
.	O
</s>
<s>
The	O
function	O
is	O
also	O
described	O
in	O
RFC	O
6986	O
and	O
one	O
out	O
of	O
hash	B-Algorithm
functions	I-Algorithm
in	O
ISO/IEC	O
10118-3:2018	O
.	O
</s>
<s>
Streebog	B-Algorithm
operates	O
on	O
512-bit	O
blocks	O
of	O
the	O
input	O
,	O
using	O
the	O
Merkle	B-Algorithm
–	I-Algorithm
Damgård	I-Algorithm
construction	I-Algorithm
to	O
handle	O
inputs	O
of	O
arbitrary	O
size	O
.	O
</s>
<s>
The	O
high-level	O
structure	O
of	O
the	O
new	O
hash	B-Algorithm
function	I-Algorithm
resembles	O
the	O
one	O
from	O
GOST	B-Algorithm
R	I-Algorithm
34.11-94	I-Algorithm
,	O
however	O
,	O
the	O
compression	O
function	O
was	O
changed	O
significantly	O
.	O
</s>
<s>
The	O
compression	O
function	O
operates	O
in	O
Miyaguchi	O
–	O
Preneel	O
mode	O
and	O
employs	O
a	O
12-round	O
AES-like	O
cipher	O
with	O
a	O
512-bit	O
block	O
and	O
512-bit	O
key	O
.	O
</s>
<s>
(	O
It	O
uses	O
an	O
8×8	O
matrix	O
of	O
bytes	O
rather	O
than	O
AES	B-Algorithm
's	O
4×4	O
matrix	O
.	O
)	O
</s>
<s>
Streebog-256	O
uses	O
a	O
different	O
initial	O
state	O
than	O
Streebog-512	O
,	O
and	O
truncates	O
the	O
output	O
hash	B-Algorithm
,	O
but	O
is	O
otherwise	O
identical	O
.	O
</s>
<s>
The	O
function	O
was	O
named	O
Streebog	B-Algorithm
after	O
Stribog	O
,	O
the	O
god	O
of	O
rash	O
wind	O
in	O
ancient	O
Slavic	O
mythology	O
,	O
and	O
is	O
often	O
referred	O
by	O
this	O
name	O
,	O
even	O
though	O
it	O
is	O
not	O
explicitly	O
mentioned	O
in	O
the	O
text	O
of	O
the	O
standard	O
.	O
</s>
<s>
Hash	B-Algorithm
values	O
of	O
empty	O
string	O
.	O
</s>
<s>
Even	O
a	O
small	O
change	O
in	O
the	O
message	O
will	O
(	O
with	O
overwhelming	O
probability	O
)	O
result	O
in	O
a	O
mostly	O
different	O
hash	B-Algorithm
,	O
due	O
to	O
the	O
avalanche	O
effect	O
.	O
</s>
<s>
In	O
2013	O
the	O
Russian	O
Technical	O
Committee	O
for	O
Standardization	O
"	O
Cryptography	O
and	O
Security	O
Mechanisms	O
"	O
(	O
TC	O
26	O
)	O
with	O
the	O
participation	O
of	O
Academy	O
of	O
Cryptography	O
of	O
the	O
Russian	O
Federation	O
declared	O
an	O
open	O
competition	B-Algorithm
for	O
cryptanalysis	O
of	O
the	O
Streebog	B-Algorithm
hash	B-Algorithm
function	I-Algorithm
,	O
which	O
attracted	O
international	O
attention	O
to	O
the	O
function	O
.	O
</s>
<s>
Ma	O
,	O
et	O
al	O
,	O
describe	O
a	O
preimage	O
attack	O
that	O
takes	O
2496	O
time	O
and	O
264	O
memory	O
or	O
2504	O
time	O
and	O
211	O
memory	O
to	O
find	O
a	O
single	O
preimage	O
of	O
GOST-512	O
reduced	O
to	O
6	O
rounds	O
.	O
</s>
<s>
They	O
also	O
describe	O
a	O
collision	B-Algorithm
attack	I-Algorithm
with	O
2181	O
time	O
complexity	O
and	O
264	O
memory	O
requirement	O
in	O
the	O
same	O
paper	O
.	O
</s>
<s>
Guo	O
,	O
et	O
al	O
,	O
describe	O
a	O
second	O
preimage	O
attack	O
on	O
full	O
Streebog-512	O
with	O
total	O
time	O
complexity	O
equivalent	O
to	O
2266	O
compression	O
function	O
evaluations	O
,	O
if	O
the	O
message	O
has	O
more	O
than	O
2259	O
blocks	O
.	O
</s>
<s>
AlTawy	O
and	O
Youssef	O
published	O
an	O
attack	O
to	O
a	O
modified	O
version	O
of	O
Streebog	B-Algorithm
with	O
different	O
round	O
constants	O
.	O
</s>
<s>
While	O
this	O
attack	O
may	O
not	O
have	O
a	O
direct	O
impact	O
on	O
the	O
security	O
of	O
the	O
original	O
Streebog	B-Algorithm
hash	B-Algorithm
function	I-Algorithm
,	O
it	O
raised	O
a	O
question	O
about	O
the	O
origin	O
of	O
the	O
used	O
parameters	O
in	O
the	O
function	O
.	O
</s>
<s>
The	O
designers	O
published	O
a	O
paper	O
explaining	O
that	O
these	O
are	O
pseudorandom	O
constants	O
generated	O
with	O
Streebog-like	O
hash	B-Algorithm
function	I-Algorithm
,	O
provided	O
with	O
12	O
different	O
natural	O
language	O
input	O
messages	O
.	O
</s>
<s>
Wang	O
,	O
et	O
al	O
,	O
describe	O
a	O
collision	B-Algorithm
attack	I-Algorithm
on	O
the	O
compression	O
function	O
reduced	O
to	O
9.5	O
rounds	O
with	O
2176	O
time	O
complexity	O
and	O
2128	O
memory	O
complexity	O
.	O
</s>
