Alice and Bob use asymmetric encryption to communicate. How many keys does Alice and Bob have combined?

Question

BlackTom AI · Accepted Answer

We start by clarifying the scenario: Alice and Bob are using asymmetric (public-key) encryption. In such a system, each participant typically has two keys: a public key (which can be shared openly) and a private key (which remains secret).

Option A: 2
This would imply that together they hold only two keys in total. If each person has a pair of keys, two keys would only account for a single person’s key pair, not both participants. Therefore, counting only two keys would seem to neglect the other party’s keys.

Option B: 4
This aligns with the standard understanding of asymmetric cryptography for two participants. Each participant possesses two keys (a public key and a private key), and when you count both participants, you have 2 keys per person × 2 people = 4 keys in total. This matches the typical setup for secure two-party communication.

Option C: 3
Having three keys in total would suggest an asymmetry in key ownership, such as one person having both keys while the other has only one, or an additional key somewhere. That does not reflect the canonical model where both parties maintain a pair of keys for encryption and decryption.

Option D: 1
Only a single key in total would be inconsistent with the concept of public-private key pairs. With public-key cryptography, at minimum each participant should have a key pair, implying more than one key overall.

Synthesis: By comparing the options, we weigh how many keys are needed when two participants use asymmetric encryption. The most coherent interpretation is that each participant maintains two keys, leading to four keys in total. The remaining options fail to capture the dual-key setup per user, either undercounting or mischaracterizing the key ownership structure.

4520_COMP_SCI_X_0006 Quiz 2

Alice and Bob use asymmetric encryption to communicate. How many keys does Alice and Bob have combined?

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