>> https://interestingengineering.com/11-cryptographic-methods-that-marked-history-from-the-caesar-cipher-to-enigma-code-and-beyond > [whether ... an encryption algo ... a comms protocol ... is not backdoored]
It is known that many things have been backdoored, many more surely are, as will many future things be. Yet it is assumed that some things are not or will not. It is known that composition of XOR's containing even just one that is not backdoored, is sufficient. But that is an estimation odds game. Your general task is to make, find, and prove ones that are not backdoored. Even then, as proofs often fall, XOR among some orthagonal risks may not be entirely unwise.
