Advanced Placement (AP) Computer Science

Which of the following best describes Hash Functions?

1. A key used in secret key cryptography.

2. A technique for converting plaintext into a fixed-length string.

3. A method for securely deleting files.

4. A process for data compression.

The correct answer is: A technique for converting plaintext into a fixed-length string.

The correct choice illustrates that hash functions are indeed a technique for converting input data of any size into a fixed-length string, referred to as a hash value or hash code. This transformation ensures that even slight changes in the input data will produce a significantly different output, which is a key characteristic of hash functions. This fixed-length output is particularly useful in various applications, such as verifying data integrity and efficiently storing data in hash tables. Hash functions play a crucial role in cryptography and data management because they provide a way to handle large amounts of data consistently. The other options do not accurately describe hash functions. While secret key cryptography does involve the use of keys for encoding and decoding data, it does not pertain specifically to the role of hash functions. Securely deleting files relates to ensuring that data cannot be recovered, which is outside the scope of what hash functions accomplish. Data compression involves reducing the size of data representations for storage or transmission and does not capture the essential features of how hash functions operate.