symmetric cryptography and asymmetr

symmetric cryptography and asymmetric cryptography.
In symmetric cryptography (e.g., Data Encryption Standard
(DES) [1], Advanced Encryption Standard (AES) [2]),
same key (i.e., K1 = K2 = K) is used in encryption (C =
EK (P)) and decryption algorithm (P = DK(C)). In asymmetric
cryptography (e.g., Rivest-Shamir-Adleman (RSA)
algorithm [1]), two different keys are used (i.e., K1 = K2),
the public key is used to encrypt a message (C = EK1 (P)),
and private key is used to decrypt the ciphertext into
plaintext (P = DK2 (C)) [1].
Strength of cryptography in respect to security depends
on the strength of keys used in encryption and decryption
algorithms. A key is said to be strong if it is not easily
guessed and not feasible to break within a real time. So,
the issue that arises is the selection of cryptographic key.
If the key is simple or very short in length, then for the