[Resource Topic] 2023/189: tlock: Practical Timelock Encryption from Threshold BLS

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tlock: Practical Timelock Encryption from Threshold BLS

Authors: Nicolas Gailly, Kelsey Melissaris, Yolan Romailler


We present a practical construction and implementation of timelock encryption, in which a ciphertext is guaranteed to be decryptable only after some specified time has passed. We employ an existing threshold network, the League of Entropy, implementing threshold BLS [BLS01, B03] in the context of Boneh and Franklin’s identity-based encryption (IBE) [BF01]. At present this threshold network broadcasts BLS signatures over each round number, equivalent to the current time interval, and as such can be considered a decentralised key holder periodically publishing private keys for the IBE where identities are the round numbers. A noticeable advantage of this scheme is that only the encryptors and decryptors are required to perform any additional cryptographic operations; the threshold network can remain unaware of the TLE and does not have to change to support the scheme. We also release an open-source implementation of our scheme and a live web page that can be used in production now relying on the existing League of Entropy network acting as a distributed public randomness beacon service using threshold BLS signatures.

ePrint: https://eprint.iacr.org/2023/189

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Go implementation is available here:

JS/TS implementation here:

And web demo here:

Let me know if anyone has questions on the topic :wink:

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