Earlier quoted context omitted.
It's more of a tree with single root and a function returning the longest tip by some distance method. Bitcoin uses amount of work proved as the distance. Bitcoin ignores other tips unless/until one of them becomes longer than the current tip but some systems like Ethereum leverage stagnant branches for their length function. But yes, dynamic-membership multi-party signature schemes and their use for creating permiss…
Straight question for the uninformed (me): Do you (or anyone else) have a technical reference for differences between the Bitcoin and Ethereum blockchain length function?
https://bitcoin.org/bitcoin.pdf
Ethereum uses a variant of the GHOST algorithm, which was introduced in the paper Accelerating Bitcoin’s Transaction Processing: Fast Money Grows on Trees, Not Chains.
https://eprint.iacr.org/2013/881.pdf
The Ethereum white paper mentions how they modified it:
https://github.com/ethereum/wiki/wiki/White-Paper#modified-g...
Full detail is in their infamously difficult Yellow Paper: