Cryptography Reference
In-Depth Information
3. The XMACR of
m
using
k
is the pair (
r, z
).
The sender transmits both
m
and the XMACR of
m
(i.e., (
r, z
))tothe
recipient, and the recipient receives
m
and (
r
,z
). The recipient then computes
r
)
z
=
f
k
(0
⊕
m
1
)
f
k
(1
1
⊕
m
2
)
f
k
(1
2
⊕
...
f
k
(1
m
n
)
n
and accepts the XMACR if and only if
z
=
z
.
11.2.3.2
Counter-Based XOR MAC
The
counter-based XOR MAC
(XMACC) construction uses a 63-bit counter
c
(instead of a random string
r
). The counter is initially set to zero and is incremented
for each message. The XMACC for message
m
is computed as follows:
1. The counter
c
is incremented by 1;
2. The value
z
is computed as follows:
z
=
f
k
(0
c
)
⊕
f
k
(1
1
m
1
)
⊕
f
k
(1
2
m
2
)
⊕
...
f
k
(1
n
m
n
)
3. The XMACC of
m
using
k
is the pair (
c, z
).
Again, the sender transmits both
m
and (
c, z
) to the recipient, and the recipient
receives
m
and (
c
,z
). The recipient then computes
c
)
z
=
f
k
(0
⊕
m
1
)
f
k
(1
1
⊕
m
2
)
f
k
(1
2
⊕
...
f
k
(1
m
n
)
n
