What is the term for the number of positions to move when encrypting a message?

• A. Offset
• B. Cipher
• C. Key
• D. Block Size

Answer: (A)

In a shift-based cipher, each letter is moved a fixed number of positions through the alphabet. That fixed amount is the offset (also known as the shift). It’s the exact measure of how far you move each character when encrypting, and knowing it lets you reverse the process by shifting in the opposite direction.

The other terms don’t fit as precisely: the cipher is the overall algorithm, the key is the secret input to the algorithm (which may relate to the shift but isn’t specifically defined as "the number of positions"), and block size refers to how many characters or bits are processed at a time in block ciphers.