 |
|
SQL Server Tips by Burleson |
Hashing
A hash is a function or algorithm, which takes a blob of data of an
arbitrary length and produces a fixed length hash value. Many
functions can take an arbitrary length of data and return a fixed
length value but what distinguishes a Hash Function is that
Given the data, it is easy to calculate the hash value.
Given the hash value, it is difficult to calculate the message from
which the hash value was calculated. This is why a Hash is also
known as a one-way function.
Given a certain blob of data, which generates a specific hash value,
it is difficult to find another blob that generates the same hash
value.
Sometimes in certain applications, another feature of hashing is
required. This is called ‘collision – resistance’ and means that it
is hard to find two random blobs that generate the same hash.
Each hash implemented in this chapter uses the syntax
“XP_AlgorithmName_HASH’
The above book excerpt is from:
Super SQL
Server Systems
Turbocharge Database Performance with C++ External Procedures
ISBN:
0-9761573-2-2
Joseph Gama, P. J. Naughter
http://www.rampant-books.com/book_2005_2_sql_server_external_procedures.htm |
