The digital signature represents one of more secure and granted methods for assertment of originality of message sender or receiver, in addition to achieve sound text of the message which has been transferred. With the expansion of using computers networks, and its growth world wide, the requirement for assertment of originality between a huge number of those who use these networks which are separated with each other for a long distances geographically, has been increased accordingly. The researches and studies centers in advanced countries have putted a great effort and time in order to manage the problem of assertment of originaiity and find a best solution to this problem. The Foundation of the RSA (Rivest, Shamir and Adleman) public-Key method is the suitable method. Indeed it is a very sophisticated method which is suitable with employment of digital signature. This latest method will achieve a great deal of advantages, one of them is the easily using of public key which is known in the guide of the networks, while every participant on the network can keep its secret Key - which is private for every one - in a more secure and safer place with him. Although, this new method identified with its accuracy and soundness, but still it suffers some time from some problems between sender and receiver of the message as a result of denying one of them as far as the signature is concerned. There-fore, it was necessary to look for a new technique, through inserting a third party called in this thesis [ARBITER] to manage the problems which appear between both parties during the operations, and to avoid them as far as he can. The aim of this thesis is to design a new and secure algorithm to present the digital signature which depends on the third party in condition of denying him to know about the original text of the message [i.e., the contain of the real message] which has been transferred. So it has been presented two new and practical algorithms for execute of the design with the purpose of fulfilling above aim. The system was implemented using an IBM-386 or compatible, an VGA monitor, Microsoft mouse, 2MB RAM, Ms-Dos 6.2 version. The programming language used to design the system was turbo pascal 7.0.