| Explanation & Hint:
Two properties of a cryptographic hash function are:
- The hash function is one way and irreversible: This means that once data has gone through the hash function, the process cannot be reversed. The resulting hash cannot be ‘decoded’ back into the original data, which is a fundamental aspect of hash functions used in cryptography.
- The output is a fixed length: Regardless of the size of the input data, a hash function for a given algorithm will always produce an output of a fixed length. For example, an MD5 hash is always 128 bits long, and a SHA-256 hash is always 256 bits long.
The other options do not correctly describe the properties of cryptographic hash functions:
- The input for a particular hash algorithm has to have a fixed size: This is incorrect. Cryptographic hash functions can process input data of any size.
- Hash functions can be duplicated for authentication purposes: This is misleading. While hash functions themselves are deterministic and will always produce the same output for the same input, the phrase “can be duplicated” is vague. In the context of authentication, hash functions are used in conjunction with other techniques (like digital signatures or HMAC) to ensure integrity and authenticity, not duplicated per se.
- Complex inputs will produce complex hashes: This is not accurate. The complexity of the input has no bearing on the complexity of the hash. A simple input can produce a hash that looks just as ‘complex’ as one from a complex input. Hash functions are designed to produce a seemingly random output that does not correlate in any simple way to the input.
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