Cryptography Reference
In-Depth Information
to B. On the right side, B knows his or her private key
k
−
B
(representing the trapdoor
information) and can use this key to invert the one-way function and decrypt
m
=
D
B
(
c
)=
D
k
−
1
B
(
c
)
.
An asymmetric encryption system is a public key cryptosystem. As such, it
can be specified by a set of three algorithms. This is done in Definition 2.10 and
illustrated in Figure 2.8.
$
&
$(
$
$
$(
!
$
Figure 2.8
The three algorithms of an asymmetric encryption system.
Definition 2.10 (Asymmetric encryption system)
An
asymmetric encryption sys-
tem
consists of the following three efficiently computable algorithms:
•
Generate
(1
n
)
is a probabilistic key generation algorithm that takes as input
a security parameter
1
n
and generates as output a public key pair (consisting
of a public key
k
and a corresponding private key
k
−
1
).
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In most literature, the security parameter is denoted by 1
k
(i.e.,
k
written in unary representation).
Because this notation may provide some confusion between
k
standing for the security parameter
and
k
standing for the public key, we don't use it in this topic. Instead, we use 1
n
to refer to the
security parameter.
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