Cryptographic hash function

What is a cryptographic hash function?
A cryptographic hash function is a type of security mechanism that generates a hash value, a message digest or a checksum value for a specific data object.

Cryptographic hash functions are implemented in information security to assess the integrity of data, authentication control, and other security mechanisms. Cryptographic hash functions generate the checksum value of a data object. If the data is changed intentionally or unintentionally, the checksum value is changed. The integrity of a data object can thus be evaluated by comparing and verifying previous and current checksums.

Cryptographic hash functions must have pre-image resistances, second pre-image resistances and collision resistance properties in order to guarantee the resistance to any cryptoclastic attack. Common examples of cryptographic hash functions are MD5 and SHA-1.