Cryptography Reference
In-Depth Information
Additionally, in
random.h
are defined the macros
bRandAES_l()
,
sRandAES_l()
,
and
lRandAES_l()
, each of which expects an initialized state buffer as argument,
and they generate random numbers of types
UCHAR
,
USHORT
,and
ULONG
from these
buffers.
The deletion of the generator takes place in analogy to RandBBS with the
following function:
Function:
deletion of the internal state of RandAES
Syntax:
void
PurgeRandAES_1 (STATEAES *rstate);
rstate
(internal state of the pseudorandom number generator)
Input:
rstate
(internal state of the pseudorandom number generator,
deleted by overwriting)
Ouput:
12.2.4 The RMDSHA-1 Generator
The following pseudorandom number generator will be built from the hash
functions SHA-1 and RIPEMD-160. Both functions can be calculated extremely
quickly, which leads to a generator with excellent performance.
With the definitions
D
:=
0
,...,
2
160
1
,C
:=
−
{
0
,...,c
−
1
}
,
S
:=
D × C
,and
R
:=
0
,...,
2
8
−
1
for input values, counters, states, and
output values, the state function is described by
φ
(
x, i
):=
RIPEMD-160(
x
)
,i
+1
mod
c
,
φ
:
S → S,
(12.6)
and the output function determined by
ψ
(
x, i
) := SHA-1(
x
)
/
2
8
·
(19
−
(
i
mod 16))
mod
2
8
.
ψ
:
S → R,
(12.7)
As in the case of RandAES, the output is varied with the help of the counter
i
in such a way that in successive steps, varying byte positions are selected as
output values. The initialization of the generator takes place via the function
InitRandRMDSHA1_l()
:
