Revisiting Elliptic++ for Bitcoin Forensics: Feature Reconstruction and Leakage-Resistant Evaluation

Elliptic and its address-level extension Elliptic++ are widely used benchmark datasets in Bitcoin forensics, cited by more than 1300 academic studies according to Google Scholar. We identify future information leakage in Elliptic++. Its positional data split does not respect temporal order, and the exact definitions of its address-level features remain undocumented. We revisit how the 55 Elliptic++ address-level features are computed and propose a leakage-resistant pipeline. First, the exact feature definitions are recovered by linking Elliptic transactions to public ledger data. Second, we compute the features with a temporal split based on each address's first appearance, using only information available at the time of prediction. Once temporal ordering is enforced, the random forest (RF)'s strong predictive performance largely disappears: its F1 score on the illicit class falls from $0.846$ under the original leaky evaluation to just $0.291$ under our leakage-resistant pipeline. Furthermore, RF no longer outperforms a simple logistic regression baseline. We provide the exact feature definitions and executable code to reproduce the leakage-resistant features, so that future Bitcoin forensic models can be evaluated based on genuine predictive capability rather than temporal data leakage.