X signs a message digitally and sends it to Y. Which of the following is required for Y to verify the authenticity of the message ?
A) X's private key B) X's public key C)Y's private key D) Y's public key
Answers
To verify the authenticity of the message Y will need b) X's public key
This whole process is called Encryption-decryption.
In the encryption part X first encrypt the message using Y's public key. Then X puts his signature using his private key and sends it to Y.
In the decryption process Y first verify the authenticity of the message by using X's public key then decrypt the message using his private key.
Hence to verify the authenticity of the message Y will need b) X's public key
X's public key is required to verify the authenticity of the message.
Short note on it:
(i) For a secure data transmission these asymmetric keys(public key and private key pair) perform encrypt and decrypt functions.
(ii) Public key is used to encrypt data(can be used to send a secure message to receiver) and the private key is used to decrypt data(with the corresponding public and private key).
(iii) In a public key encryption, data encrypted using the recipients public key and it cannot be decrypted without using a matching private key. similarly, the data encrypted using private key can only be decrypted using matching public key.
(iv) Private key is symmetrical and public key is asymmetrical. Private key is quite faster compared to public key and also the key must be kept secret.
Small Example on keys:
If A wants to send data to B, he will encrypt the data with the B's public key. Only B has access to her corresponding Private key. As only B has access to her private key, it is possible that only b can decrypt the encrypted data. Even if someone else gains access to the encrypted data, it will remain confidential as they should not have access to B's private key.
Hope it helps!