Two users, UserA and UserB, are engaging in secure communication using only asymmetrical encryption. UserA needs to send a secure message to UserB. What occurs first? A. UserB sends UserA UserB's public key

B. UserA sends UserB UserA's private key

C. UserA sends a secret key to UserB

The correct answer is A: UserB sends UserA UserB's public key

Explanation:

In Asymmetrical Encryption, the both user involve in the secure communication must have a pair of key called public and private key. There are various step involves with engaging in Asymmetrical encryption, they include:

1. Each user generates a pair of keys to be used for the encryption and decryption of messages.

2. Each user places one of the two keys in a public register or other accessible file. This is the public key. The companion key is kept private.

3. If User B wishes to send a confidential message to User A, User B encrypts the message using User A's public key.

4. When User A receives the message, User A decrypts it using her private key. No other recipient can decrypt the message because only User A knows User A's private key.

Therefore, from the steps above, Option B and C are wrong because the private key/secret key should never be shared between users in asymmetrical encryption.

Option A is the correct answer as UserB sends UserA UserB's public key which is available to the everyone.