Which cryptographic concept ensures that data integrity is preserved and cannot be altered during transmission?

Hash Functions are a fundamental cryptographic tool for ensuring data integrity. They generate a fixed-length hash value (digest) from input data. Any change in the input, even by a single bit, results in a completely different hash value, making tampering evident. For instance, if a file's hash is computed before transmission and verified upon receipt, any alteration to the file will produce a mismatched hash. Algorithms like SHA-256 are commonly used. Hash functions are widely applied in digital signatures and certificates to validate integrity and detect unauthorized changes. Why Other Options Are Incorrect :

1. Symmetric Key Encryption : Ensures confidentiality but does not directly verify integrity.
2. Asymmetric Key Encryption : Protects data through key pairs but does not ensure integrity by itself.
3. Digital Signatures : While they ensure integrity, they use hash functions internally and offer additional authentication.
4. Public Key Infrastructure (PKI) : Manages keys and certificates but doesn’t directly compute integrity checks.