Advantages and Disadvantages of Asymmetric or Public Key Cryptography


  • Security is easy as only the private key must be kept secret.
  • Maintenance of the keys becomes easy being the keys (public key/private key) remain constant through out the communication depending on the connection.
  • As the number of keys to be kept secret become less.


  • This is not suitable for encryption of large messages as the encryption/decryption throughput is inversely related to the key length.

Digital Signature Algorithm (DSA):

            DSA is a secured public key encryption algorithm. DSA has been addressed by the National Institute of Standards and Technology (NIST) from the digital signature method defined by its Digital Signature Standard. This has been proposed as the substitution for the hand written signatures and it provides the attributes for authentication as a paper based document. It has been accepted all over the world and DSA is being implemented for business transactions and legal documents.

            DSA uses the private key for signing the document, for which it has been processed by the hashing algorithms (SHA-1 or MD5), and the resultant hash values and the private key are given as the input for the DSA to create the signature.

At the receiver end public key of receiver and sender key is used for the verification of the signature. With this the authentication and integrity of the message will be satisfied. Key’s used by DSA are in between 512 to 1024 bits which in turns makes DSA much slower. Hence RSA is used for authentication.

            Inspite of DSA being slower than RSA as the key size of the DSA is more which in turn makes encryption stronger. Hence we will be using this for the initial key establishment and handshaking when once it is completed we will be using symmetric key encryption algorithm (AES_128) for further communication of messages.

This Project Paper is written & submitted by Deepak V.