SRP is a secure password-based authentication and key-exchange protocol. It solves the problem of authenticating clients to servers securely, in cases where the user of the client software must memorize a small secret (like a password) and carries no other secret information, and where the server carries a verifier for each user, which allows it to authenticate the client but which, if compromised, would not allow the attacker to impersonate the client. In addition, SRP exchanges a cryptographically-strong secret as a byproduct of successful authentication, which enables the two parties to communicate securely

srp4net is a library that implements the SRP authentication protocol for a Javascript client against a C# webservice.