A digital signature is a cryptographic technique that verifies the authenticity and integrity of a message or document, by using a hash function and an asymmetric encryption algorithm. A hash function is a mathematical function that transforms any input data into a fixed-length output value called a digest, which is unique for each input. An asymmetric encryption algorithm uses two keys: a public key and a private key.
The public key can be shared with anyone, while the private key must be kept secret by the owner. To create a digital signature, the sender first applies a hash function to the plaintext message to generate a digest. Then, the sender encrypts the digest with their private key to produce the digital signature. To verify the digital signature, the receiver decrypts the digital signature with the sender's public key to obtain the digest. Then, the receiver applies the same hash function to the plaintext message to generate another digest. If the two digests match, it means that the message has not been altered and that it came from the sender. The security of a digital signature depends on the secrecy of the sender's private key. If an attacker obtains the sender's private key, they can create fake digital signatures for any message they want, thus compromising the control provided by the digital signature. Reversing the hash function using the digest is not possible, as hash functions are designed to be one-way functions that cannot be inverted. Altering the plaintext message will result in a different digest after applying the hash function, which will not match with the decrypted digest from the digital signature, thus invalidating the digital signature. Deciphering the receiver's public key is not relevant, as public keys are meant to be publicly available and do not affect the security of digital signatures.

The best way to reduce the risk of inaccurate or misleading data proliferating through business intelligence systems is to establish rules for converting data from one format to another, because this ensures that the data quality and integrity are maintained throughout the data transformation process. Data conversion rules define the standards, procedures, and methods for transforming data from different sources and formats into a common format andstructure that can be used by the business intelligence systems12. Implementing data entry controlsfor new and existing applications, implementing a consistent database indexing strategy, and developing a metadata repository to store and access metadata are not the best ways to reduce the risk of inaccurate or misleading dataproliferating through business intelligence systems, becausethey do not address the issue of dataconversion, which is a critical step in the data integration process for business intelligence systems. References: 1: CISA Review Manual (Digital Version), Chapter 4, Section 4.3.3 2: CISA Online Review Course, Module 4, Lesson 3

A fire alarm system is a device that detects and alerts people of the presence of fire or smoke in a building. A fire alarm control panel is the central unit that monitors and controls the fire alarm system. The most effective location for the fire alarm control panel would be inside the booth used by the building security personnel.
This is because:
* The security personnel can quickly and easily access the fire alarm control panel in case of an emergency, and take appropriate actions such as notifying the fire department, evacuating the building, or resetting the system.
* The fire alarm control panel can be protected from unauthorized access, tampering, or damage by the security personnel, who can also monitor its status and performance regularly.
* The fire alarm control panel can be isolated from the computer room, which may be exposed to higher risks of fire or smoke due to the presence of electrical equipment, such as uninterruptible power supply (UPS) modules or server computers.
* The fire alarm control panel can be connected to the computer room through a dedicated communication line, which can ensure reliable and timely transmission of signals and information between the two locations.
References:
* [1]: Fire Alarm Control Panel - an overview | ScienceDirect Topics
* [2]: Fire Alarm Control Panel - What is it and how does it work? | Fire Protection Online
* [3]: Fire Alarm Control Panel Installation Guide - XLS3000 - Honeywell

Hash totals are a control technique used to ensure data integrity during batch processing. A hash total is a calculated value based on the data in a batch. This value is compared to a pre-calculated hash total to confirm that all data has been processed correctly and without alteration.
References
ISACA CISA Review Manual (27th Edition): Hash totals are discussed within the context of batch processing controls.
Other Auditing Resources: Hash totals are a fundamental control technique discussed in various audit and information security publications.