the present invention relates to a method and arrangement in a communications system and more specifically to digital signatures sent over bandwidth restricted connections . the objective of the present invention is to provide a way to enable a mobile public network user to use his / her mobile device for performing digital signing of data suitable for being transferred partially over a bandwidth restricted radio link to a receiver such as a payment server or similar . a digital signature is created within a mobile device and transferred the over the radio access network to the gateway , a certificate associated to the specific mobile device is retrieved by means of an agent associated to the gateway , said retrieved certificate is attached to the digital signature by means of said agent ; and said digital signature and attached certificate forwarded over the internet to the receiver .