Cryptography allows people to carry out business electronically without
worries of deceit and deception. D
ata communications channels are often
insecure. The security can be either by passive intruder where an in
intercepts messages to view the data or by an active intruder where an
intruder modifies the intercepted messages.
he best way of protecting
messages against the active and passive threats inherent in data
transmissions is cryptography. Cryptograph
y is the science of
decrypting of information. Encryption is the process of mapping the readable
text to cipher text (unreadable format) and decryption the process of
remapping the cipher text into the plain text.
The mapping process is a
quence of mathematical computations
which do not affect the meaning of
Thus cryptography plays an important role in secureness of data.
hundreds of thousands of people interact electronically,
whether it is through
commerce, ATM machines, or cellular phones.
atellite TV companies use cryptography to overcome the problem of
people getting free TV.
The perpetual increase of
electronically has increased
reliance on cryptography.
used widely from Internet
a variety of other
common household items. Without cryptography, hackers could get into our
, listen in on our phone conversations, tap into our cable companies and
acquire free cable service, or break into our bank
One of the hardest problems in cryptography is the creation of the keys
themselves, a process which usually req
uires a good random number source.
High quality random numbers are surprisingly hard to come by on computer
systems, which are almost completely deterministic by nature.
When the message is encrypted it can be decrypted using a public key
(which is known
to all). And by using different messages, the corresponding
secret key can be interpreted. The sender
using secret key do not actually
know whether the
secret key is still secret or it has been
detected by some
If the information
is to be transferre
d is to be a
then there must
be a key between the receiver and sender. And both
need to agree on
encode/decode messages. But you don't want to keep using the
same key, or you will make it easier and easier for others to crack you
But it's also a pain to get keys to
others whom you wish to transfer a secret
There are different ways in encrypt/decrypt messages.
There are lot of
algorithms which are user to develop the encryption/de
different method of forming encrypted message and their algorithm are give
Algorithms for development
HAVAL, MD2, MD4, MD5, SHA
RC2, RC5, RC6
In case of message digest Secured Hash Algorithm (SHA)
1 is most widely
used. The message digest produced is 160 bit and hence they are found to be
1 is called secure because it is computationally
ble to find a message which corresponds to a given message digest, or
to find two different messages which produce the same message digest. Any
change to a message in transit will, with very high probability, result in a
different message digest, and the s
ignature will fail to verify.
Key encryption widely used is RSA.
RSA is a
) is a public
key encryption scheme
combining the RSA algorithm with the OAEP method.
Key Encryption tec
hnique uses RC6 algorithm, which is the latest and
the most popularly used algorithm for Private
Other public key systems include knapsack ciphers (largely broken) and
elliptic curve cryptosystems (not widely used).