Security Algorithm and Protocol Types
Algorithm Types
There are two types of security algorithms:
 Symmetric  There is one key both for encryption and decryption or else one key can be calculated using the other. The keys must be distributed in secret.
 Public Key  One key is public and is used for either encryption or decryption depending on whether the public party is sending a message or receiving it. The other key is private and allows only encryption or decryption. One key cannot be used to calculate the value of the other key.
Protocol Types
 Arbitrated Protocol  A third party arbitrates the protocol to ensure no party is cheated.
 Adjudicated  A third party is called in only if a dispute during the execution of the protocol arises.
 Self enforcing  No arbitrator is used and the protocol itself ensures fairness.
DEA  Data encryption algorithm
Algorithm Basics
Encryption algorithms are very complex mathematical formulas and in order to be effective utilize repeated and usually shifted mathematical operations. This means that an operation is done, bits are shifted and the operation is done again. This may be repeated several times. There are several factors that affect the security of the algorithm but having the best of these factors does not ensure the algorithm will be hard to crack or break. Many algorithms operate on data in blocks. The factors that characterize algorithms are:
 Key length
 Block length
 Number of rounds of identical operations called function f where data is combined with the key. The bits are shifted in various ways and recombined using various methods.
In order to determine the effectiveness of the cryptographic algorithm, experts must attempt to break it using various attacks described in the section "Security Attacks".
