INTRODUCTION

Internet accelerates economical flows by online promotion and the selling of material or immaterial products. It allows the creation of new commercial schemes (auctions...) by connecting information. Companies and private individuals exchange through Internet digital contract documents. However in the modern world we cannot rely on the security of our communication networks. It is practically impossible to physically protect all the links from interference. The use of cryptography to protect communication paths is well established and has undergone significant advances in the last 20 years.

The problem about Internet is that the individuals who communicate do not meet and do not know each other. They do not know if the interlocutor is reliable. The solution to solve this problem is the Digital Signature. The protocol allows two users to exchange a secret key over an insecure medium without any prior secrets.

A Digital Signature is an electronic signature that can be used to authenticate the identity of the sender of a message, or of the signer of a document. It can also be used to ensure that the original content of the message or document that has been conveyed is unchanged.

This technology was first defined in the early 1980s with the development of public key cryptography but has received renewed interest as an authentication mechanism on Internet.

This process has been created to full several aims:

➢ Integrity: It allows guaranteeing to the receiver that the document has not been modified. ➢ Confidentiality: Thanks to the Digital Signature, we cannot reveal the document of someone else. ➢ Authentication: This technology ensures the identity of the sender. ➢ Non-repudiation: The receiver has the proof of the transaction.

In a first chapter, we will explain how the Digital Signature works and will talk about the limits concerning the commercial, technical and law aspects in the sector of e-business in a second