By Ethan Heilman (Boston Uni), Neha Narula (MIT Media Lab), Garrett Tanzer (Harvard), James Lovejoy (MIT Media Lab), Michael Colavita (Harvard), Madars Virza (MIT Media Lab), and Tadge Dryja (MIT Media Lab)
We present attacks on the cryptography formerly used in the IOTA blockchain, including under certain conditions the ability to forge signatures. We developed practical attacks on IOTA’s cryptographic hash function Curl-P-27, allowing us to quickly generate short colliding messages. These collisions work even for messages of the same length. Exploiting these weaknesses in Curl-P-27, we broke the EU-CMA security of the former IOTA Signature Scheme (ISS). Finally, we show that in a chosen-message setting we could forge signatures and multi-signatures of valid spending transactions (called bundles in IOTA).