Can the creator of all the encrytion algorithm hack our accounts?

Question

If let's say for example the creator of MD5. He created the MD5. So can he hack our accounts or other sites that are using this algorithm?

And not just MD5, other encryption algorithms too. How is it possible that it says it is almost impossible to hack those that are using these algorithms, they are design by human too.

Please explain

Answer 1

The only advantage the inventor has, is a good understanding of the algorithm. He can try to insert a backdoor or a weakness, but well known algorithms are analyzed by many independend cryptographers, and hopefully they would discover such weaknesses (intended or not).

As long as you do not have a thorough understanding of the matter yourself, you will always have to trust in other people. So the longer an algorithm withstood crypto analysis, the more likely it is that you can trust it.

Answer 2

The creators of cryptosystems should not be able to easily break them, because the security of a soundly designed cryptosystem should only depend on the secrecy of the keys. This is known as Kerckhoff's Prinicple.