In cryptography, a preimage attack on a cryptographic hash differs from a collision attack. In a preimage attack, the attacker starts with a particular output, and is able to find an input that will produce that particular output, whereas a collision attack merely finds two inputs that produce the same output. Cryptography has had a long and colourful history. ... In cryptography, a cryptographic hash function is a hash function with certain additional security properties to make it suitable for use as a primitive in various information security applications, such as authentication and message integrity. ... A collision attack on a cryptographic hash tries to find two different inputs that will produce the same hash value, i. ... A collision attack on a cryptographic hash tries to find two different inputs that will produce the same hash value, i. ...

For example, there is a program called CRC Faker that will generate a file of a user-defined size with the CRC requested.