Cryptography is the secret writing art or science of transmission and storage the data through
the insecure network. Cryptography has a long history, in twentieth century cryptography
were most significant tools to protect the military, the diplomatic service and government and
protect national secrets and strategies. “The most striking development in the history of
cryptography came in 1976 when Diffie and Hellman published New Directions in
Cryptography. In 1978 Rivest, Shamir, and Adleman discovered the first practical public-key
encryption and signature scheme, now referred to as RSA” (Alfred J., 1996) The RSA
method is based on hard mathematical problem, the intractability of factoring large integers.
RSA application of a hard mathematical difficulty to cryptography revitalized hard work to
find more competent methods to factor. “The 1980s saw major advances in this area but
none which rendered the RSA system insecure. Another class of powerful and practical
public-key schemes was found by ElGamal in 1985” (Alfred J., 1996) these are also based on
the discrete logarithm problem. Some algorithm works good in some area and other protocol
and algorithm another, are used to communicate securely over an insecure network. The most
important security goal is secrecy or confidentiality of data. Cryptography is method of
Encryption and Decryption. Cryptology stands for combination of Cryptography with
Cryptanalysis.
RSA is a public key cryptography; where key is the challenging issue which to be
considering selecting a protocol for securing a computer system. Public-key cryptography is
use of asymmetric key algorithms instead of or in addition to symmetric key algorithms. An
asymmetric key algorithm does not require a secure initial exchange to both sender and
receiver. The asymmetric key algorithms are used to produce a mathematically related key
pair and published secret private key as a public key. This is a protection of the authenticity
of a message and creating of a digital signature for message with the public key. This can be
verified using the private key and also allows protection of the privacy and integrity of a
message, the message can only be decrypted using the private key.
In difference, the symmetric-key algorithms which have been used for some thousands of
years using a single secret key shared for both sender and receiver and kept private for both
encryption and decryption. In symmetric encryption scheme, the sender and receiver must
securely share a key in progress. As because symmetric key algorithms are practically always
much less computationally intensive and common to exchange a key using a key-exchange
algorithm, transmit the data using that key and a symmetric key algorithm.