Hi Leif Monday, October 20, 2003, 10:53:05 AM, you wrote:
LG> Hello Vishal, LG> Monday, October 20, 2003, 2:29:01 AM, you wrote: V>> That's exactly what I meant. If all 5 people have the same public V>> key, they would all also need a copy of the private key to decrypt V>> it. LG> No *Yes*. All 5 would have to have the private key to decrypt this message, if it were encrypted using the *same* public key. LG> , if you encrypt a message using my public key, and Marck's public key, and LG> Allie's public key, then any one of us could decrypt the message using our LG> own private key. We are talking about different things. You're talking about multiple recipients for one message, which indeed works as you described. I am talking about encrypting multiple times, with the base for the new iteration being the ciphertext produced by the previous one. A message/file encrypted using this procedure could not be decrypted by simply using any one of the recipients' private keys. LG> I won't pretend I know how it works, but it's not encryption on encryption, LG> but a way of encrypting it that any one of use could decrypt it using our LG> own private key. Let me see if I can explain it. PGP actually uses both symmetric and asymmetric encryption. What happens is this: the initial message is encrypted using the symmetric algorithm you chose (IDEA, 3DES, whatever) using a one-time, randomly generated 'session key'. This key is then encrypted using the public key algorithm(RSA, DH/DSS, whatever) that you chose. The encrypted key is then sent to the recipient together with the text encrypted by your symmetric algorithm. While decrypting, the recipient uses his private key to decrypt the session key, and then uses this key to decrypt the message. When sending to multiple recipients, it is actually the session key that is encrypted with each of the recipients' public keys. This is why the message can be decrypted using any one of them. Cheers, -- Vishal ________________________________________________ Current version is 2.01 | "Using TBUDL" information: http://www.silverstones.com/thebat/TBUDLInfo.html
