A Level Computer Science OCR Practice Exam

What is the outcome of hashing?

1. Restoration of original data

2. Unpredictable output for any input

3. Retrieval of the original message

4. Mapping input of arbitrary size to fixed output

The correct answer is: Mapping input of arbitrary size to fixed output

The outcome of hashing is primarily to map input data of arbitrary size to a fixed-size output, which is known as the hash value or hash code. This process is essential in various computing applications, including data integrity verification, password storage, and digital signatures. When data is hashed, no matter how large or complex the original input is, the result will always be a hash of a consistent size, often represented in hexadecimal format. This fixity allows systems to efficiently compare data without needing to store or handle the entire original input. Hash functions are designed to produce outputs that are practically unique for different inputs, thus minimizing the risk of collisions, where two different inputs yield the same hash value. This mapping functionality is crucial for performance in databases and for establishing security protocols. It ensures that data can be processed, stored, and compared without needing to reveal or reconstruct the original data, which enhances security and privacy. In contrast, while unpredictable output for any input is a desirable property of good hash functions, it is not the main outcome; thus, unpredictability is a characteristic rather than a definitive outcome. Similarly, restoration or retrieval of the original message does not occur with hashing, as hashes are one-way functions by design—once data has been hashed,