Patent attributes
According to one aspect of the present invention there is provided a method of preparing second protocol data for transmitting over a first protocol network comprising the steps of compressing the data to be transmitted in accordance with the first protocol, to produced first protocol compressed data and encrypting the first protocol compressed data in accordance with the first protocol to produce first protocol compressed and encrypted data. The invention consists of a means for the client to indicate to the first hop proxy that it wishes S/MIME encryption to be applied to part of an outgoing message. The first hop proxy then applies this encryption on behalf of the client. The encryption is therefore applied after the message has traversed the end terminal link. On the first proxy link, the message is sent without S/MIME encryption and can therefore benefit from compression (before the first hop IPSEC encryption is applied). A second aspect of the invention allows the support of end-to-end compression to be negotiated between end devices so that SIP compression can be applied to data before it is encrypted using S/MIME by the end system.
