Question

The __ key(s) plays a significant role in the encryption and decryption of blocks.

Answer 1

Keys is your answer dear ☺️.

Hope it's helps you.

Thanks...✊✊

Answer 2

Key

We have to understand a concept, whenever we have a word which is singular then the verb following it has (s).

And if the word is plural the verb will not have (s).

For example:

A tiger sleeps......

The dogs bark.

The key plays a significant role in the encryption and decryption of blocks.