RSA decrypt with public key ?

Linux and Unix-Like Linux
1

Dear All,
I need to decrypt with private key most of the time and this works for RSA. At times I need to decrypt with public key (data is encrypted with private key). This does not seem to work via VB.Net. Is there support for such an activity in Java on Linux or Windows ? Please advise.

Thanks,
Sushma

2

Public key cryptography always works the same way: Encryption is done with the public key, decryption done with the private key. It is not possible to decrypt anything with the public key (otherwise the whole system would crash down). The only time it's done the other way is for message authentication, where only a digest of a message is encrypted and can be verified (not decrypted) using the public key.

3

Thanks pludi. I intend to use it for the following reason :

Encryption-sender's-private key[ hash[Public key certificate of sender] ||
hash[Private key of sender] ]
on the sending side and to match this with computed value on the receiver's side.

Thanks,
Sushma

4

So you want to send the hash value of the senders private key and have it signed too. That's basically key Authentication, and there are already quite a lot of protocols out there for that.
With PKC it's never possible to decrypt anything with the public key (except if it's per chance your own private key). If you want to send messages between 2 parties using PKC, you'll have to generate a key pair for both sides.