Institution: PROBASHI KALLYAN BANK Exam: অফিসার (জেনারেল) (05-05-2023) || 2023
Topic: ICT (তথ্য ও যোগাযোগ প্রযুক্তি), Subject: Computer and ICT (তথ্য ও যোগাযোগ প্রযুক্তি)

Best Answer Explained in Below-:

The process referred to in the question, "conversion of data onto code," aligns with the definition of encryption. Encryption is a method of transforming readable data, known as plaintext, into an unreadable format called ciphertext, using specific algorithms and keys. The primary purpose of encryption is to protect sensitive information from unauthorized access and ensure its confidentiality during storage or transmission.

For instance, when data is sent over the internet, encryption secures it so that even if it is intercepted, it cannot be easily understood by anyone who does not have the appropriate decryption key. This essential security mechanism is crucial in various applications that involve sensitive information, such as online banking, messaging services, and secure communications in general.

In contrast, the other options presented are distinct concepts: a firewall is a network security device that monitors and controls incoming and outgoing network traffic, a digital certificate is used to verify the identity of entities in digital communications, and a password is a secret word or phrase used for authentication purposes. Therefore, the correct answer to the question is indeed **A) encryption**.