Paper 2021/715

Hours of Horus: Keyless Cryptocurrency Wallets

Dionysis Zindros


We put forth a keyless wallet, a cryptocurrency wallet in which money can be spent using a password alone, and no private keys are required. It requires a smart contract blockchain. We propose two schemes. In the first, the user sets a short wallet password and can spend their money at a prespecified maturity date using the password alone. Using this as a stepping stone, we propose a second scheme, in which the user uses an OTP authenticator seed to generate a long series of time-based OTP passwords for the foreseeable future. These are encrypted and organized in a Merkle tree whose root is stored in a smart contract. The user can spend funds at any time by simply visually providing the current OTP password from an air gapped device. These OTPs can be relatively short: Just $6$ alphanumeric characters suffice. Our OTP scheme can work in proof-of-stake as well as static and variable difficulty proof-of-work blockchains. The low-entropy in the passwords and OTPs in our scheme is protected from brute force attempts by requiring that an adversary accompany any brute force attempt by a transaction on the chain. This quickly incurs enormous economic costs for the adversary. Thus, we develop the first decentralized rate limiting scheme. We use Witness Encryption (WE) to construct a timelock encryption scheme in which passwords are encrypted from past into future blocks by leveraging the NP-language expressing proof-of-work or proof-of-stake performed as the witness. Witness Encryption is a currently impractical cryptographic primitive, but our scheme may become practical as these primitives are further developed.

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Publication info
Published elsewhere. Financial Cryptography and Data Security Workshop on Trusted Smart Contracts 2022
cryptographic protocolsblockchainwallets
Contact author(s)
dionyziz @ gmail com
2022-02-10: last of 2 revisions
2021-05-31: received
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      author = {Dionysis Zindros},
      title = {Hours of Horus: Keyless Cryptocurrency Wallets},
      howpublished = {Cryptology ePrint Archive, Paper 2021/715},
      year = {2021},
      note = {\url{}},
      url = {}
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