Fundamentally, there are two types of cryptosystems based on the manner in which encryption-decryption is carried out in the system −

Symmetric Key Encryption

Asymmetric Key Encryption

The main difference between these cryptosystems is the relationship between the encryption and the decryption key. Logically, in any cryptosystem, both the keys are closely associated. It is practically impossible to decrypt the ciphertext with the key that is unrelated to the encryption key.