Copyright © 2021 cryptalgo - All Rights Reserved.
At least in the United States, copyright itself is inherently and automatically created as soon as an idea is "fixed in a tangible medium of expression".
The "Copyright © $YEAR $COPYRIGHT_HOLDER" boilerplate is not the mechanism by which that right is created. Rather, that statement makes explicit claims about the creation date and holder of that implicit right.
If one were to consider the cryptographic security of those claims, one might define a cryptographic game InfringeCopyright and attempt to prove an upper bound on the advantage wielded by some class of adversaries (subject to certain restrictions on computational power). Such analysis is beyond the scope of this website for two reasons: