Question

How do you send an encrypted signed message from Alice to Bob with RSA?

Answer 1

To send an encrypted signed message using RSA, Alice signs the message with her private key and encrypts it with Bob's public key. Bob then decrypts the message with his private key and verifies the signature using Alice's public key. This confirms the message's confidentiality, authenticity, and integrity.

Step-by-step explanation:

To send an encrypted signed message from Alice to Bob using RSA, the following steps are typically involved:

1. Alice first creates the message she wants to send to Bob.
2. She then generates a hash of the message using a secure hash function (such as SHA-256).
3. Alice uses her private key to sign the hash, creating the digital signature.
4. She then uses Bob's public key to encrypt both the original message and the digital signature.
5. The encrypted message and signature are sent to Bob.
6. Upon receiving the data, Bob uses his private key to decrypt the content.
7. Bob then uses Alice's public key to verify the digital signature by decrypting it to reveal the hash.
8. He generates a hash of the decrypted message and compares it to the decrypted signature hash. If they match, it confirms both the message's integrity and Alice's identity as the sender.

This process ensures that the message is confidential (because only Bob can decrypt it with his private key), authentic (since the message is signed by Alice's private key), and retains integrity (as verified by the hash).