Q: 10
What is the effective key size of DES?
Options
Discussion
B is wrong, A. Effective key size in DES means the actual bits used for encryption, not with the parity bits included. Seen it asked this way before so I'd pick A here.
A. Saw this in recent exam reports too, always came up as 56 bits for effective key size.
Option A is correct, but only because they're asking "effective" key size. That trips people up since the actual key is 64 bits including parity. I've seen a similar question sneak in that catch before.
Pretty sure it's A here. Effective key size for DES is 56 bits, since parity bits aren't actually used for encryption. Agree?
Its A for sure, since "effective key size" means only the 56 bits used after dropping parity. The 64 bits answer is tempting but that's including the parity ones, not actual usable key material. Pretty common ISC2 trap. Someone correct me if I'm missing anything.
A that's what I saw on a similar question in one of my practice exams. 56 bits is the real strength, not the full key. Not 100 percent sure if they ever try to trick with B though.
A seen this a lot in practice sets. Clear and straightforward question.
A imo, since the question is about effective key size, not the whole key with parity. DES only uses 56 bits for encryption, rest are parity bits. Saw this in other practice sets too. Let me know if anyone thinks differently.
B tbh, since DES uses a 64-bit key overall (counting parity bits). Easy to mix up with effective key size though, but I'd pick B if they just mean total length. Correct me if that's off.
Likely A, lots of practice tests and the official ISC2 book mention 56 bits as the effective key size.
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