Yes, and trust in enforcement of the patent is also essential.
Henry Bessemer invented an ingenious process for producing bronze powder (used in "gold" paint). It was a very efficient method compared to the time-honored system of using manual labor to pound sheets of bronze into flakes.
In his autobiography Bessemer explained why he decided to keep the process secret instead of relying on a patent. He was concerned that a patent could easily be violated by duplicating his machinery in small colonies that do not respect English patents. Only the bronze powder would be imported and there would be no proof that it was produced using his method.
So Bessemer built a small factory to produce bronze powder and kept the full details of the process secret by compartmentalizing the different stages of the operation. The workers in the different rooms did not even see each other and would even enter the factory by different entrances.
It was an elaborate and probably expensive way to protect his idea but it worked for decades.
As the Kentucky Historical Society incoherently relates, in their description of the Kentucky Landmark, “Kelly Kettle” :
One of many kettles made in this area by William Kelly, used for making sugar down South. In 1851, Kelly discovered process, known as Bessemer, for manufacture of steel. An Englishman, Bessemer, obtained patents on same process in England 1855 and in U.S. 1856. Kelly filed priority claim, 1857. U.S. awarded patent to Kelly and later refused renewal to Bessemer.
... the thing is, Big Steel sided with Bessemer, so the law was on the losing side of history along with Kelly. I recall reading or hearing that Kelly claimed that Bessemer visited his furnace sites in disguise and stole his process, and that there is some basis for believing Kelly’s claim.
Everything you know is wrong! Dogs came from the stars! The Aztecs invented the vacation! The brain is not the boss! All I know is everything YOU know is WRONG!
The formula for Coca Cola is not patented either. Trade secrets are yours as long as you can keep them a secret. Patents are only good for 20 years...