Cryptography is defined as a means of protecting private information against unauthorized access in cases where physical security is difficult to achieve.
Cryptography carried out using two basic operations:
Encryption: The process of transforming intelligible information (plaintext) into an unintelligible form (ciphertext).
Decryption: The process of transforming the information from ciphertext to plaintext.
The encryption algorithm has the following form: C = E(P,Ke)
P = plaintext to encrypted
Ke = encryption key
C = resulting ciphertext
The decryption algorithm performed by the same matching function which has the following form:
P = D(C,Kd)
C = ciphertext to decrypted
Kd = decryption key
P = resulting plaintext
Asymmetric cryptosystem uses the same key for both encryption and decryption.
Also, It necessary that the key should be easily alterable if required and always kept secret.
Moreover, This implies that the key known only to authorized users.
Symmetric cryptosystems also called the shared key or private key cryptosystems since both sender and receiver share the same key. o P=Dk(Ek(P))
In the Asymmetric Cryptosystems, the keys used for encryption and decryption are different but they form a unique pair.
There are separate keys for encryption (Ke) and decryption (Kd).
P = DKd(EKe(P))
Moreover, One key in the asymmetric cryptosystem kept private while the other one made public.
Hence these types of cryptosystems referred to as public key systems.