Abstract: 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 (104) for performing digital signing of data suitable for being transferred partially over a bandwidth restricted radio link to a receiver (102) such as a payment server or similar. A digital signature is created within a mobile device (104) and transferred the over the radio access network (108) to the gateway (110), a certificate associated to the specific mobile device is retrieved by means of an agent (116) associated to the gateway (110), said retrieved certificate is attached to the digital signature by means of said agent (116); and said digital signature and attached certificate forwarded over the Internet (106) to the receiver (102).