Define the following security terms:

a) Digital signature.
b) Hash function.
c) Symmetric-key encryption.
d) Digital certificate.
e) Denial-of-service attack.
f) Worm.
g) Message digest.
h) Collision.
i) Triple DES.
j) Session keys.

a) Digital signature.
ANS: A digital signature is used for authentication and is the electronic equivalent of a handwritten signature, which is considered to be just as valid as a handwritten signature. It is derived from a hash function applied to the message.
b) Hash function.
ANS: A hash function is a calculation done on a message to create the message digestused in a digital signature.
c) Symmetric-key encryption.
ANS: Also known as secret-key encryption, this method uses the same key to encrypt and decrypt a message.
d) Digital certificate.
ANS: A digital certificate is granted by a certificate authority and used in PKI. A digital certificate provides a user’s public key, plus information such as the name of the person and organization to which the certificate has been issued.
e) Denial-of-service attack.
ANS: A DoS attack is any attack in which loss of normal functionality results. For
example, flooding Web servers with an enormous amount of data packets results in
the denial of service to legitimate users.
f) Worm.
ANS: A worm is a program, similar to a virus, that seeks to move across a network,
spreading itself to as many computers as possible.
g) Message digest.
ANS: A message digest is the result of the calculations performed during a hash function. The message digest is used as a digital signature for a message.
h) Collision.
ANS: Collision occurs when two different situations present the same result. Collision
in digital signatures occurs when two separate messages produce the same message digest.
i) Triple DES.
ANS: A symmetric key algorithm that consists of three passes through the DES algorithm.
j) Session keys.
ANS: A secret key that was generated by a key distribution center with the purpose of being used in one transaction or session.