- The length, in bits, of a key (6).
- The total number of possible combinations arising from a given key length (1). The greater the key length, the greater the protection against a brute force attack. A 64-bit encryption key has over 1.8 × 1019 possible combinations, a 128-bit key over 3.4 × 1038, and a 256-bit key has over 1.1 × 1077 combinations.
- synonymkey space