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Digital certificates
Digital certificates
Definition
Digital certificates are electronic files that act like on-line passports. There are two
types of certificates.
■
Self-signed certificates.
Self-signed certificates are certificates that web servers create.
■
Certificates signed by a certificate authority.
Trusted third parties - Certificate authorities (CA) - issue the certificates. After
the CA receives a request, the CA checks the identity of the holder of the
certificate and signs the certificate. Then the certificate is sent back.
Secure connections
A digital certificate, given to a web server, helps to secure the connections on the
Internet in two ways.
■
The web server can prove uniquely the identity of the server to client machines.
■
The data that is exchanged on-line is encrypted and protected from theft or
tampering.
How digital certificates work
Before a client machine sends confidential information to a web server, the client
machine accesses the digital certificate of the server. The digital certificate includes
the public encryption key of the web server. The client machine uses the certificate
to start the following procedures that are described in the Secure Socket Layer (SSL)
protocol.
■
Analyse the certificate and authenticate the identity of the web server.
■
Encrypt the information that is sent to the web server.
Validity check of the certificates
Your browser approves the validity of a certificate when the certificate meets the
following requirements.
■
The CA that signed the certificate is on the list of trusted CAs that is installed on
your browser. If the certificate is self-signed, the certificate must be on the list of
trusted certificates that is installed on your browser.
■
The validity period has not been expired.
■
The common name of the certificate matches the URL of the web server.
If the certificate does not meet one or more of the three requirements above, the
browser displays a security alert. The browser asks you if you trust the certificate.
Refer to the on-line help of your browser for information about the handling of the
security alerts displayed for digital certificates.