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Wireless Security White Paper 15
Digital Certificates
Digital certificates are electronic files that can be used as unique identifiers for people and
resources over networks. A digital certificate binds a user’s identity to a public key, thus
establishing trust. Digital certificates can also be used to help secure confidential communication
between two parties. A certificate typically includes the following information relating to its
owner and to the Certificate Authority (CA) that issued it:
•
The name of the holder and other uniquely identifying detail such as the URL of the Web
server using the certificate and the holder’s e-mail address
•
The holder’s public key, which can be used to encrypt sensitive information for the certificate
holder
•
The name of the Certification Authority (CA) that issued the certificate
•
A serial number
•
The validity period (or lifetime) of the certificate (a start and end date)
When the issuing CA creates the certificate, it digitally signs the information on the certificate.
The CA’s signature on the certificate is like a tamper-detection seal; any tampering with the
contents is easily detected.
Figure 7 illustrates digital certificates.
Figure 7: Digital Certificates
Subject DN: cn=Bob Smith,
o=ACME, c=US
Serial #: 8391037
Start:1/5/97 1:02
End:7/5/98 1:02
CRL:cn=CRL2, o=ACME, c=US
SubjectAltName: IP, DNS, email
Key:
What’s in a certificate?
CA DN: o=ACME, c=US
Unique name of owner
Unique serial number
Period of validity
Revocation information
Public key
Name of issuing CA
CA’s digital
signature
Alternate Subject identifiers