Red Hat CERTIFICATE 7.1 ADMINISTRATOR, Руководство администратора

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Internet Security Issues
768 Red Hat Certificate System Administrator’s Guide • September 2005
• Tampering. Information in transit is changed or replaced and then sent on to the
recipient. For example, someone could alter an order for goods or change a person's
resume.
• Impersonation. Information passes to a person who poses as the intended recipient.
Impersonation can take two forms:
• Spoofing. A person can pretend to be someone else. For example, a person can pretend
to have the email address
jdoe@example.net
, or a computer can identify itself as a
site called
www.example.net
when it is not. This type of impersonation is known as
spoofing.
• Misrepresentation. A person or organization can misrepresent itself. For example,
suppose the site
www.example.net
pretends to be a furniture store when it is really
just a site that takes credit-card payments but never sends any goods.
Normally, users of the many cooperating computers that make up the Internet or other
networks don’t monitor or interfere with the network traffic that continuously passes
through their machines. However, many sensitive personal and business communications
over the Internet require precautions that address the threats listed above. Fortunately, a set
of well-established techniques and standards known as public-key cryptography make it
relatively easy to take such precautions.
Public-key cryptography facilitates the following tasks:
• Encryption and decryption allow two communicating parties to disguise information
they send to each other. The sender encrypts, or scrambles, information before sending
it. The receiver decrypts, or unscrambles, the information after receiving it. While in
transit, the encrypted information is unintelligible to an intruder.
• Tamper detection allows the recipient of information to verify that it has not been
modified in transit. Any attempt to modify data or substitute a false message for a
legitimate one will be detected.
• Authentication allows the recipient of information to determine its origin—that is, to
confirm the sender’s identity.
• Nonrepudiation prevents the sender of information from claiming at a later date that the
information was never sent.
The sections that follow introduce the concepts of public-key cryptography that underlie
these capabilities.