In order to achieve the security for the e-business application, generally the organizations follow the cryptographic methods. The two widely accepted and used cryptographic methods are symmetric and asymmetric. The DES ideally belongs to the category of symmetric key cryptosystem and RSA, NTRU belongs to the category of asymmetric key cryptosystem. Symmetric key ciphers use the same key for encryption and decryption, or the key used for decryption is easily calculated from the key used for encryption. Symmetric key ciphers can be broadly grouped into block ciphers and stream ciphers. Symmetric encryption has a troublesome drawback i.e., two people who wish to exchange confidential messages must share a secret key. The key must be exchanged in a secure way. Key distribution is difficult among the parties. .RSA is one of the oldest and the most widely used public key cryptographic algorithms. It was the first algorithm known to be suitable for signing as well as encryption. The system works on two large prime numbers, from which the public and private keys will be generated. NTRU (Nth degree truncated polynomial ring units) is a collection of mathematical algorithms based on manipulating lists of very small integers. NTRU is the first secure public key cryptosystem not based on factorization or discrete logarithmic problems. The keys are generated by having small potent polynomials from the ring of truncated polynomials. Finally we proceed with the key generation, encryption and decryption of the plain text required by implementing the algorithms of both the cryptosystems. Though the limitations are there in the symmetric key cryptosystem, we proposed and tested all the methods for variable sized text files. This paper presents the comparative study of DES, RSA and NTRU algorithms for variable sized text files as input and the results were observed, analyzed and compared so as to identify which method is appropriate to the business needs.