With SSL implemented on both the client and server, your Internet communications are transmitted in encrypted form. Information you send can be trusted to arrive privately and unaltered to the server you specify (and no other).
To what degree can SSL security protect me?
SSL uses authentication and encryption technology developed by RSA Data Security Inc. For example, Netscape Navigator's export implementation of SSL (U.S. government approved) uses a medium-grade, 40-bit key size for the RC4 stream encryption algorithm. The encryption established between you and a server remains valid over multiple connections, yet the effort expended to defeat the encryption of one message cannot be leveraged to defeat the next message.
A message encrypted with 40-bit RC4 takes on average 64 MIPS-years to break (a 64-MIPS computer needs a year of dedicated processor time to break the message's encryption). The high-grade, 128-bit U.S. domestic version provides protection exponentially more vast. The effort required to break any given exchange of information is a formidable deterrent. Server authentication uses RSA public key cryptography in conjunction with ISO X.509 digital certificates.
Netscape Navigator and Netscape Commerce Server deliver server authentication using signed digital certificates issued by trusted third parties known as certificate authorities. A digital certificate verifies the connection between a server's public key and the server's identification (just as a driver's license verifies the connection between your photograph and your personal identification. Cryptographic checks, using digital signatures, ensure that information within a certificate can be trusted.
To evaluate the strategic and quantitative implications of the SSL implementation of certification and public key technology, consult the SSL Protocol specification via the Help/On Security menu item.