Explanation/Reference:
The sender private key is used to calculate the digital signature
The digital signature is used to achieve integrity, authenticity and non-repudiation. In a digital signature, the sender's private key is used to encrypt the message digest (signing) of the message and receiver need to decrypt the same using sender's public key to validate the signature.
A digital signature (not to be confused with a digital certificate) is an electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a document, and possibly to ensure that the original content of the message or document that has been sent is unchanged. Digital signatures are easily transportable, cannot be imitated by someone else, and can be automatically time-stamped. The ability to ensure that the original signed message arrived means that the sender cannot easily repudiate it later.
A digital signature can be used with any kind of message, whether it is encrypted or not, simply so that the receiver can be sure of the sender's identity and that the message arrived intact. A digital certificate contains the digital signature of the certificate-issuing authority so that anyone can verify that the certificate is real.
How It Works
Assume you were going to send the draft of a contract to your lawyer in another town. You want to give your lawyer the assurance that it was unchanged from what you sent and that it is really from you.
You copy-and-paste the contract (it's a short one!) into an e-mail note.
Using special software, you obtain a message hash (mathematical summary) of the contract.
You then use a private key that you have previously obtained from a public-private key authority to encrypt the hash.
The encrypted hash becomes your digital signature of the message. (Note that it will be different each time you send a message.) At the other end, your lawyer receives the message:
To make sure it's intact and from you, your lawyer makes a hash of the received message.
Your lawyer then uses your public key to decrypt the message hash or summary.
If the hashes match, the received message is valid.
Below are some common reasons for applying a digital signature to communications:
Authentication
Although messages may often include information about the entity sending a message, that information may not be accurate. Digital signatures can be used to authenticate the source of messages. When ownership of a digital signature secret key is bound to a specific user, a valid signature shows that the message was sent by that user. The importance of high confidence in sender authenticity is especially obvious in a financial context. For example, suppose a bank's branch office sends instructions to the central office requesting a change in the balance of an account. If the central office is not convinced that such a message is truly sent from an authorized source, acting on such a request could be a grave mistake.
Integrity
In many scenarios, the sender and receiver of a message may have a need for confidence that the message has not been altered during transmission. Although encryption hides the contents of a message, it may be possible to change an encrypted message without understanding it. (Some encryption algorithms, known as nonmalleable ones, prevent this, but others do not.) However, if a message is digitally signed, any change in the message after signature invalidates the signature. Furthermore, there is no efficient way to modify a message and its signature to produce a new message with a valid signature, because this is still considered to be computationally infeasible by most cryptographic hash functions (see collision resistance).
Non-repudiation
Non-repudiation, or more specifically non-repudiation of origin, is an important aspect of digital signatures.
By this property, an entity that has signed some information cannot at a later time deny having signed it.
Similarly, access to the public key only does not enable a fraudulent party to fake a valid signature.
Note that these authentication, non-repudiation etc. properties rely on the secret key not having been revoked prior to its usage. Public revocation of a key-pair is a required ability, else leaked secret keys would continue to implicate the claimed owner of the key-pair. Checking revocation status requires an
"online" check, e.g. checking a "Certificate Revocation List" or via the "Online Certificate Status Protocol".
Very roughly this is analogous to a vendor who receives credit-cards first checking online with the credit- card issuer to find if a given card has been reported lost or stolen. Of course, with stolen key pairs, the theft is often discovered only after the secret key's use, e.g., to sign a bogus certificate for espionage purposes.
Tip for the exam:
Digital Signature does not provide confidentiality. The sender's private key is used for calculating digital signature Encryption provides only confidentiality. The receiver's public key or symmetric key is used for encryption The following were incorrect answers:
Sender's Public key - This is incorrect as receiver will require sender's private key to verify digital signature.
Receiver's Public Key - The digital signature provides non-repudiation. The receiver's public key is known to every one. So it can not be used for digital-signature. Receiver's public key can be used for encryption.
Receiver's Private Key - The sender does not know the receiver's private key. So this option is incorrect.
The following reference(s) were/was used to create this question:
CISA review manual 2014 Page number 348
http://upload.wikimedia.org/wikipedia/commons/2/2b/Digital_Signature_diagram.svg
http://en.wikipedia.org/wiki/Digital_signature
http://searchsecurity.techtarget.com/definition/digital-signature

Explanation/Reference:
Explanation:
Sniffing is an attack that can be used to capture sensitive pieces of information (e.g., a password) passing through the network. Encryption is a method of scrambling information to prevent unauthorized individuals from understanding the transmission. Spoofing is forging an address and inserting it into a packet to disguise the origin of the communication. Data destruction is erasing information or removing it from its original location.

Section: Protection of Information Assets
Explanation:
Experience has demonstrated that reliance purely on preventative controls is dangerous. Preventative
controls may not prove to be as strong as anticipated or their effectiveness can deteriorate over time.
Evaluating the cost of controls versus the quantum of risk is a valid management concern. However, in a
high-risk system a comprehensive control framework is needed, intelligent design should permit additional
detective and corrective controls to be established that don't have high ongoing costs, e.g., automated
interrogation of logs to highlight suspicious individual transactions or data patterns. Effective access
controls are, in themselves, a positive but, for reasons outlined above, may not sufficiently compensate for
other control weaknesses. In this situation the IS auditor needs to be proactive. The IS auditor has a
fundamental obligation to point out control weaknesses that give rise to unacceptable risks to the
organization and work with management to have these corrected. Reviewing background checks on
accounts payable staff does not provide evidence that fraud will not occur.

The risk-based approach is designed to ensure audit time is spent on the areas of highest risk. The development of an audit schedule is not addressed by a risk-based approach. Audit schedules may be prepared months in advance using various schedulingmethods . A risk approach does not have a direct correlation to the audit staff meeting time budgets on a particular audit, nor does it necessarily mean a wider variety of audits will be performed in a given year.