 of the information. Thus, public key electronic signatures provide authentication and data integrity. An electronic signature also provides non-repudiation, which means that it prevents the sender from claiming that he or she did not actually send the information. 6.10.4 WHY PUBLIC KEY INFRASTRUCTURE? How can you prove who you are over the Internet? In 'real life' you use some type of identification card (for example a driving license or a passport) to prove who you are. In the world of only ones and zeros, the digital certificate is your ID card. The ID cards in real life are distributed according to strict rules to avoid someone else getting hold of your ID card. The way of handling digital certificates is what PKI is all about. PKI is a way to solve the problem of the management of keys. In a large system, with thousands of users, there must be some automatic way of managing keys for encryption and authentication. With key management, we usually mean: generation of keys and digital certificates distribution of keys and digital certificates storage of keys and digital certificates validation of keys and digital certificates revocation of keys and digital certificates expiry of keys and digital certificates A consequence of the encryption is the need for keys in order to understand the message. Key handling requires what is called 'secure associations'. The PKI standard allows a single login to a system with the aid of a 'smart card'. This card contains a private key, and the public key is stored in a directory. This requires a trusted party to act as Certification Authority (CA), issuing necessary certificates (Figure 6.20). Certification authority Security gateway LDAP (lightweight directory access protocol) Figure 6.20 The need for a Certification Authority Understanding Changing Telecommunications - Building a Successful Telecom Business The protocol LDAP is used to get the public key from the directory. Once again, it is important to know you are talking to the right person, and that nobody pretends to be 