What is the key length used for DES?

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Multiple Choice

What is the key length used for DES?

Explanation:
DES uses a 56-bit key. The key is supplied as 64 bits, but eight of those bits are parity bits and do not contribute to the DES key schedule. The actual cryptographic material is 56 bits, which drives the subkeys for the 16 rounds, giving an effective key space of 2^56. The other numbers aren’t DES key lengths—for example, a 64-bit key would include parity bits that don’t increase security, while 128-bit and 40-bit keys aren’t used for DES.

DES uses a 56-bit key. The key is supplied as 64 bits, but eight of those bits are parity bits and do not contribute to the DES key schedule. The actual cryptographic material is 56 bits, which drives the subkeys for the 16 rounds, giving an effective key space of 2^56. The other numbers aren’t DES key lengths—for example, a 64-bit key would include parity bits that don’t increase security, while 128-bit and 40-bit keys aren’t used for DES.

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