RSA, Diffie-Hellman (DH), and elliptic curve cryptography (ECC) like public key cryptography algorithms have proved their significance before the era of quantum cryptography. The security of RSA is based on the factorization problem, while the security of DH and ECC is based on the problem of secret logarithm problem. These problems are considered hard to solve with the current computation facilities. However, these problems would be easy to solve with the quantum computer. This leads to the search for another cryptographic algorithm that can be sustained in the era of quantum computers. The algorithm must be computationally secure and efficient such that it should not be solved by even a quantum computer. Few of the candidate algorithms are based on lattice. Many researchers have provided literature to explain the workings of lattice-based cryptography. In this chapter, a very simple but concrete explanation is given. Also, the possible attacks and countermeasures are discussed.