Cryptography Reference
In-Depth Information
Protocol 1.1
The notation used for protocols.
A
B
(input parameters)
(input parameters)
...
...
computational step
computational step
...
...
−
...
←−
...
...
computational step
computational step
...
...
(output parameters)
(output parameters)
the result of the protocol execution. Similar to the input parameters, the output
parameters must not necessarily be the same on either side of the protocol execution.
In many cases, however, the output parameters are the same (and represent the result
and the common output of the protocol execution).
1.2.1
Classes of Cryptographic Systems
Cryptographic systems may or may not use secret parameters (e.g., cryptographic
keys). Furthermore, if secret parameters are used, then they may or may not be
shared between the participating entities. Consequently, there are at least three
classes of cryptographic systems that can be distinguished,
3
and these classes are
characterized in Definitions 1.5-1.7.
Definition 1.5 (Unkeyed cryptosystem)
An
unkeyed cryptosystem
is a crypto-
graphic system that uses no secret parameter.
Definition 1.6 (Secret key cryptosystem)
A
secret key cryptosystem
is a crypto-
graphic system that uses secret parameters that are shared between the participating
entities.
Definition 1.7 (Public key cryptosystem)
A
public key cryptosystem
is a crypto-
graphic system that uses secret parameters that are not shared between the partici-
pating entities.
In Chapter 2, we introduce and briefly overview some representatives of
unkeyed, secret key, and public key cryptosystems. These representatives are further
3
This classification scheme is due to Ueli Maurer.
