As we have seen in this chapter, public-key cryptography can be used for encryption and key exchange. Furthermore, it has some properties (such as nonrepudiation) which are not offered by secret key cryptography. So why do we still use symmetric cryptography in current applications?

Disadvantages of public key cryptography is that : Assymetric cryptography is slower than the private key cryptography.

Explanation:

We are dealing with big data applications most of time. Almost all applications are data intensive. Private key cryptography which is also known as symmetric cryptography. Symmetric cryptography based systems are faster. Since there is no key transmitted with the data, encrypted data can be transferred over the channel or session even if the path is vulnerable or have chances of interception as the chances of decrypting the data is almost impossible.

Also, The identity of the receiver is guaranteed using the password based authentication used by symmetric crypto systems. Only the trusted receiver who has the access to the secret key can only decrypt the payload

Public Key Cryptography is slower than private key cryptography. Today's application's are data intensive. In case of data intensive applications, encrypting huge data will take a lot more time than that of symmetric key cryptography. Whenever Bulk data transmission is needed symmetric key cryptography is preferred. Secret key based crypto systems have proven to be more faster than any currently available assymetric key based crypto systems.