Please can someone explain the difference between a cryptographic ‘Key Space’ and ‘Key Length’

Question

I’ve just started a cryptography section of an exam I’m studying for and I just don’t understand these terms. Please can someone explain what they are and how they differ from different algorithms – thanks! 🙂

In: 2

Answer 1

Key length is the number of bits in the key. Key space is the set of all possible keys.

For example, if the key is 128 bits long, then the key length is 128 while the key space is all the 2^128 possible 128-bit keys.