Certified Bitcoin Professional Practice Exam

What is true about a cryptographic hash?

1. It is reversible

2. It is a one-way mathematical function

3. It can be easily decoded

4. It requires a public key for verification

The correct answer is: It is a one-way mathematical function

A cryptographic hash is fundamentally designed to be a one-way mathematical function. This means that once data is transformed into a hash through this process, it cannot be converted back to its original form. The primary purpose of a cryptographic hash is to create a unique representation of data, ensuring integrity and security. It takes an input (or "message") and produces a fixed-size string of characters, which appears random but is actually derived from the input in a deterministic manner. This one-way characteristic is crucial in various applications, including digital signatures and data integrity checks, as it helps ensure that any modifications to the data will result in a completely different hash value. This feature is what allows users to verify data integrity: if two hashes produced from the same input are identical, the data is unchanged. In contrast, the other options misrepresent the properties of a cryptographic hash. A cryptographic hash is not reversible; once you hash data, you cannot easily retrieve the original input. It also cannot be easily decoded, as the intention is to avoid revealing any information about the original data. Lastly, verification of a hash does not require a public key; rather, it relies on the hash itself, which can be readily generated and compared without the need for