Clarification on public key decryption

Question

I have a key pair and I use private key to encrypt the data, public key for decryption. Is it possible to provide confidentiality in this setup ?

You're not "encrypting" with a private key, you're signing. You're not "decrypting" with a public key, you're verifying the signature. — Bruno, May 21 '14 at 10:13

score 3 · Answer 1 · answered May 21 '14 at 07:25

3

No, it's not. You must encrypt data using recipient's public key to have confidentiality. Now all you have are integrity and authenticity (you've got a variation of digital signature, actually)

answered May 21 '14 at 07:25

DarkWanderer

8,739
1
25
56

score 0 · Answer 2 · answered May 16 '15 at 02:50

In the setup that you're asking about, anyone who had access to the recipient's public key (which could be a lot of people if it's truly public) could then decrypt the message, so no, there is no real confidentiality.

If you want to provide both authenticity and confidentiality, you might try encrypting the data with the recipient's public key in order to provide confidentiality, then encrypting (or signing) that with your private key. The recipient would then decrypt (or verify) that data by decrypting it with your public key, thus indicating that the data really came from you, and then decrypting that data using their private key thus helping to ensure confidentiality.

Clarification on public key decryption

2 Answers2