Hi

I want to encrypt a string of data on my server using a private key and then subsequently decrypt the data on a end user's client machine using the corresponding public key. I want to use the following code:

Server Code:

Certificate cert = Certificate.CreateFromPfxFile("MyPrivateCertFile.pfx", "password");
RSA public_key = cert.PublicKey;
RSAPKCS1KeyExchangeFormatter kef = new RSAPKCS1KeyExchangeFormatter(public_key);
byte[] encrypted = kef.CreateKeyExchange(data);

client Code:

Certificate cert = Certificate.CreateFromCerFile("MyPublicCertFile.cer");
RSA private_key = cert.PrivateKey;
RSAPKCS1KeyExchangeDeformatter ked = new RSAPKCS1KeyExchangeDeformatter(private_key);
byte[] decrypted = ked.DecryptKeyExchange(encrypted);

The server code appears to encrypt correctly but the client code throws an exception of "Bad Key". The only was this works is is I encrypt with the public key and decrypt with the provate key. Obviously I don't want to have the provate key sttored on the end user's machine so how can I encrypt on the server using the private key and then subsequently decrypt on the client's machine using the public key?

Thanks

Jim

Sorry, ignore the last post I put in the wrong sample code - this one demonstrates what I'm trying to do:

Hi

I want to encrypt a string of data on my server using a private key and then subsequently decrypt the data on a end user's client machine using the corresponding public key. I want to use the following code:

Server Code:

Certificate cert = Certificate.CreateFromPfxFile("MyPrivateCertFile.pfx", "password");
RSA private_key = cert.PrivateKey;
RSAPKCS1KeyExchangeFormatter kef = new RSAPKCS1KeyExchangeFormatter(private_key);
byte[] encrypted = kef.CreateKeyExchange(data);

client Code:

Certificate cert = Certificate.CreateFromCerFile("MyPublicCertFile.cer");
RSA public_key = cert.PublicKey;
RSAPKCS1KeyExchangeDeformatter ked = new RSAPKCS1KeyExchangeDeformatter(public_key);
byte[] decrypted = ked.DecryptKeyExchange(encrypted);

The server code appears to encrypt correctly but the client code throws an exception of "Bad Key". The only was this works is is I encrypt with the public key and decrypt with the provate key. Obviously I don't want to have the provate key sttored on the end user's machine so how can I encrypt on the server using the private key and then subsequently decrypt on the client's machine using the public key?

Thanks

Jim

You can't encrypt with the private key and decrypt with the public key -- this is a limitation of asymmetric cryptography.