CHAPTER 6: OPERATIONAL GUIDE
OPERATIONAL GUIDE
MULTINET4 MULTI-PORT SERIAL SERVER & MANAGED SWITCH – INSTRUCTION MANUAL
6–15
6.5.3.1 RSA Public Key Cryptography
RSA public key cryptography is the most popular of the so-called asymmetric
cryptography algorithms. Unlike symmetric cryptography, which uses a single key for
encryption and decryption operations, asymmetric cryptography uses a pair of keys. One
of the keys is published and well-known while the other is private and is known only to its
owner. Information encrypted by the public key can only be decrypted by the private key
and vice versa. This special property is what allows us to use asymmetric cryptography as
a way of creating digital signatures.
6.5.3.2 Digital Signatures
Digital signatures provide a way of verifying that an electronic document was generated
by a certain entity. Digital signatures protect electronic documents against tampering and
forgery.
Digital signatures may be created using RSA public key cryptography. The basic technique
involves creating a message digest of a plaintext document and then encrypting the result
with the author’s private key. The original plaintext document and the digested/encrypted
version (the signature) are passed to a recipient who then decrypts the signature using the
author’s public key and compares the result to the message digest of the original plaintext
document. If there is a match, the signature is valid.
SSL authentication involves validating the digital signature on an electronic document
known as an X.509 certificate.
6.5.3.3 X.509 Certificates
An X.509 certificate is an electronic document used to publish a public key. It generally
contains additional information that describes the certificate owner’s name, organization,
and contact information. The certificate is digitally signed by a trusted third-party to prove
its authenticity. Certificates may be chained, with each certificate in the chain holding the
RSA public key of the entity that signed the previous certificate. In this way, a “chain of
trust” is established from the entity being authenticated to a mutually trusted third party
known as a Certificate Authority.
6.5.3.4 Certificate Authority
A Certificate Authority (CA) is usually a well-known, trusted entity that issues signed
certificates for entities that wish to distribute their RSA public key. You can think of a CA as
the equivalent of notary public for the Internet.
A CA has its own RSA public and private key pair that it uses to sign X.509 certificates. It
publishes its public key in a root X.509 certificate that is self-signed. This means that there
is no way to digitally verify the authenticity of a root CA certificate. You must choose which
root CA certificates to trust. Often, root CA certificates are distributed “out-of-band” or
bundled with software that uses SSL.
6.5.3.5 Multinet4 Certificate Files
Multinet4 does not come with any bundled or pre-installed root CA certificates. You must
generate or otherwise acquire these certificate files and install them on each unit. This is
accomplished through the “
Security: Certificates
” screen. To use an installed certificate, you
