What are cryptographic hash functions and how do they work?

a) They are encryption methods used to hide data, working by converting data into a fixed-size string of bytes.
b) They are algorithms used for compressing data, ensuring efficient storage and transmission.
c) They are mathematical functions that take an input and produce a fixed-size string of characters, used for data integrity verification.
d) They are methods of converting text into a secret code, typically used in military communications.