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The security of individual keys was widely studied with practical solutions available, from mnemonic phrases to dedicated hardware. There are also techniques for securing funds by requiring combinations of multiple keys. However, to the best of our knowledge, a crucial question was never addressed: How is wallet security affected by the number of keys, their types, and how they are combined? This is the focus of this work.

We evaluate the security (complement of failure probability) of wallets based on the number and types of keys used. Our analysis covers a wide range of settings and reveals several surprises.