Tze Jin WongLee Feng KooFatin Hana NaningAhmad Fadly Nurullah Bin RasedeeMohamad Maulana MagimanMohammad Hasan Abdul Sathar2024-05-272024-05-2720212021-12-21857-83652076-5010.37418/amsj.10.11.5https://oarep.usim.edu.my/handle/123456789/3205The public key cryptosystem is fundamental in safeguard communication in cyberspace. This paper described a new cryptosystem analogous to El-Gamal encryption scheme, which utilizing the Lucas sequence and Elliptic Curve. Similar to Elliptic Curve Cryptography (ECC) and Rivest-Shamir-Adleman (RSA), the proposed cryptosystem requires a precise hard mathematical problem as the essential part of security strength. The chosen plaintext attack (CPA) was employed to investigate the security of this cryptosystem. The result shows that the system is vulnerable against the CPA when the sender decrypts a plaintext with modified public key, where the cryptanalyst able to break the security of the proposed cryptosystem by recovering the plaintext even without knowing the secret key from either the sender or receiver.enciphertext, cubic, elliptic curve, Lucas sequence, plaintextArticle343934471011