Alle 09:53, venerd́ 28 novembre 2003, Dietmar Maurer ha scritto: > >> Actually, you can encrypt the message once, to each of the keys > >> of each of the people on the list. You don't have to do multiple > >> encryptions. That would save a hell of a lot of processing overhead.
> Sorry, I dont underdstand that suggestion. You want to put several > encrypted messages into one mail? (I dont know much about public key > systems). That would increase the size of the message? Or is it possible > to encrypt a message once so that several people can decrypt it? Basically, public key encryption works like this: 0. you compress the original plaintext file (e.g. gzip), to reduce redundancy 1. you choose a random key, tipically in the range 128->256 bits 2. you encrypt the compressed plaintext file with this key, using a traditional simmetric algorithm, (e.g. 3DES) 3. for each receiver you encrypt *that random key* with the receiver's public key, using a public key algorithm, (e.g. RSA) 4. you pack everything and send the bundle to all receivers So the encrypted email size is roughly made up of: sizeof(compressed_plaintext) + N*[sizeof(random_key) + sizeof(receiver_id)] Where N is the number of receivers. So OK, the size grows with the number of receivers, but not that much. Moreover, for N < M the encrypted email is smaller that the original plaintext (due to compression). M depends on achieved compression ratio. -- Simone Piunno, chief architect Wireless Solutions SPA - DADA group Europe HQ, via Castiglione 25 Bologna web:www.wseurope.com tel:+390512966811 fax:+390512966800 God is real, unless declared integer _______________________________________________ Mailman-Developers mailing list [EMAIL PROTECTED] http://mail.python.org/mailman/listinfo/mailman-developers
