Symmetric key cryptography:-

• The biggest obstacle in successfully deploying a symmetric-key algorithm is the necessity for a proper exchange of PRIVATE keys. This transaction must be completed in a secure manner. If face to-face meeting, which proves quite impractical in many circumstances when taking distance and time into account, cannot be possible to exchange private keys. If one assumes that security is a risk to begin with due to the desire for a secret exchange of data in the first place, the exchange of keys becomes further complicated.
• Another PROBLEM CONCERNS the compromise of a private key. In symmetric key cryptography, every participant has an identical private key. As the number of participants in a transaction increases, both the risk of compromise and the consequences of such a compromise increase dramatically. Each additional user adds another potential point of weakness that an attacker could take advantage of. If such an attacker succeeds in GAINING control of just one of the private keys in this world, every user, whether there are hundreds of users or only a few, is completely compromised.
• Both Symmetric and Asymmetric-key cryptography also has vulnerabilities to attacks such as the man in the middle attack. In this situation, a malicious third party intercepts a public key on its way to one of the parties involved. The third party can then instead pass along his or her own public key with a message claiming to be from the original sender. An attacker can use this process at every step of an exchange in order to successfully impersonate each member of the conversation without any other parties having knowledge of this deception.

Asymmetric cryptography –More secure!

• Asymmetric keys must be many times longer than keys in symmetric-cryptography in order to boast security. While generating longer keys in other algorithms will usually prevent a brute force attack from succeeding in any meaningful length of time, these computations become more computationally intensive. These longer keys can still vary in effectiveness depending on the computing power available to an attacker.

Symmetric key cryptography:-

Asymmetric cryptography –More secure!