Cryptography embodies a sophisticated methodology that utilizes encryption and decryption techniques to safeguard sensitive information during online transactions. It serves as a fundamental cornerstone of secure e-commerce, effectively shielding customers' data from the malevolent designs of cyber criminals. Galois/Counter Mode (GCM) is a mode of operation for symmetric-key cryptography block ciphers, widely acclaimed for its exceptional performance. AES-GCM distinguishes itself as a prevalent cryptography algorithm specifically engineered for Authenticated Encryption with Associated Data (AEAD), ensuring both data confidentiality and integrity. This paper elucidates a Java implementation of AES-GCM (Galois/Counter Mode), meticulously crafted to protect sensitive data in online shopping, particularly concerning the safeguarding of credit card information during transmission or storage. This implementation exemplifies the process of encrypting customer data prior to its transmission to a server, followed by subsequent decryption on the server side. Such an implementation guarantees robust security for online shopping transactions.