Tham khảo tài liệu 'hacker professional ebook part 182', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Another major advantage of public-key systems is that they can provide a method for digital signatures. Authentication via secret-key systems requires the sharing of some secret and sometimes requires trust of a third party as well. A sender can then repudiate a previously signed message by claiming that the shared secret was somehow compromised by one of the parties sharing the secret. For example the Kerberos secret-key authentication system 79 involves a central database that keeps copies of the secret keys of all users a Kerberos-authenticated message would most likely not be held legally binding since an attack on the database would allow widespread forgery. Public-key authentication on the other hand prevents this type of repudiation each user has sole responsibility for protecting his or her private key. This property of public-key authentication is often called non-repudiation. Furthermore digitally signed messages can be proved authentic to a third party such as a judge thus allowing such messages to be legally binding. Secret-key authentication systems such as Kerberos were designed to authenticate access to network resources rather than to authenticate documents a task which is better achieved via digital signatures. A disadvantage of using public-key cryptography for encryption is speed there are popular secret-key encryption methods which are significantly faster than any currently available public-key encryption method. But public-key cryptography can share the burden with secret-key cryptography to get the best of both worlds. For encryption the best solution is to combine public- and secret-key systems in order to get both the security advantages of public-key systems and the speed advantages of secret-key systems. The public-key system can be used to encrypt a secret key which is then used to encrypt the bulk of a file or message. This is explained in more detail in Question in the case of RSA. Public-key cryptography is not meant to replace .
