Bachelor / Master Thesis

Blockchain and BlockDAG protocols

Blockchain and BlockDAG protocols aim to build a robust ledger that can be used for recording payments and transfer of assets, such as coins, tokens, or other digital claims. Transfers occur in transactions that are written in blocks that refer to a single parent block, in the case of blockchain protocols, or to multiple parents, in the case of BlockDAG protocols.

Many prominent blockchain protocols use the longest-chain rule introduced by Nakamoto with Bitcoin [1]. According to this rule, miners select the longest chain of blocks, i.e., the chain containing the largest number of blocks, as a ledger. This means that if two blocks are not part of the same chain, one of them will be wasted. BlockDAG protocols instead select the ledger in a more general manner. As a result, the ledger has the form of a directed acyclic graph (DAG) [2], and DAG-based protocols often offer a higher transaction throughput.

A natural research question arises: can one improve the transaction throughput of existing protocols by replacing the longest chain selection with a DAG-based selection?

Two main objectives of this thesis are: (i) assessing the inefficiency of existing protocols due to the longest chain selection rule and (ii) implementing an upgrade to a longest-chain protocol by converting it to a BlockDAG protocol (more details can be provided upon request).


[1] Bitcoin

[2] DAG

Contact Ignacio Amores Sesar or Duc V. Le for more information.

Nature of the project: Theory 30%, Systems 70%.