A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size to
a fixed-size output. It's designed to be a one-way function, making it practically
impossible to invert or reverse the process.
Key Properties of Hash Functions:
- Deterministic: The same input will always produce the same output.
- Quick Computation: It's efficient to calculate the hash value for any
given input.
- Pre-image Resistance: It should be computationally infeasible to
reverse a hash value to its original input.
- Small Changes, Big Differences: A small change in the input should
produce a significantly different hash output.
- Collision Resistance: It should be difficult to find two different
inputs that produce the same hash output.
Common Uses of Hash Functions:
- Password storage (with additional security measures like salting)
- Data integrity verification
- Digital signatures
- File or data identification
- Blockchain technology
Security Note: While hash functions are designed to be secure, some older
algorithms (like MD5 and SHA-1) have known vulnerabilities and are not recommended for
security-critical applications.