Computer Science for IGCSE & O level - Data Transmission (Section 10 - No. 47)

What is the role of a 'key' in the process of encryption?

To verify the identity of the sender.

To transform the plaintext into ciphertext.

To compress the data for faster transmission.

To create a digital signature.

The key is used as input to the encryption algorithm, transforming plaintext into ciphertext.