Checksums must be always the same



The checksum of the file on the user's device must be always  the same as the checksum of the same file by the SW author.



Verification of  the files is important for the functioning of the operating system and other programs (* .exe, * .dll).  If the checksums  from users and SW authors are identical, therefore it is certain that the file has not been modify by a computer virus or hacker.




Checksum contains :

- Name of file and extension
- File size
- Hash A
- Hash B ( with a different algorithm than Hash A )


Talk about the specific type of hash functions is now premature. It is essential that the combination of file size and the two hash codes generated by two different algorithms gives great security to ensure the integrity of each file.  This is the real strength.