Jotasapiens

A peer-to-peer, permisionless cryptographic voting system that relies only on the existence of generic digital signatures and encryption.        

Tthe hash-based one-time signatures python library is updated to version 5.

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Code downloads are back online. Now the python implementations of hash-based signatures has its own project site: JotaSigs. The site is kindly hosted by TuxFamily (France). Check it out!

New research on hash-based, post-quantum cryptography.

Hash-based signatures are typically stateful: they need to keep a state with the number of past signatures to know which values have been already used and cannot be reused.

If the memory storing the state fails, the security would degrade. Some implementations solve the problem by using a number of secret values so large that the probability of picking the same at random is negligible, but this solution can make the signatures impractical for some real world applications.

In a new paper, we propose a new approach to hash-based signatures: we show that it is possible to derive their state entirely from time, without the need to keep a state with the number of past signatures.

From One to Many: Synced Hashed-Based Signatures (2017)

In known hash-based, many-times signatures, the cost and the size of each signature increase as the number of needed signatures increase. As a result, it is usually believed that signatures based on hashes need more computation and much larger sizes than classical signatures. We introduce a construction to challenge that idea: we show that it is possible to construct a many-times signatures scheme that is more efficient than the OTS it is built from, rather than less. We study the generation of signatures in conjunction with a blockchain, like bitcoin. The proposed scheme permits an unlimited number of signatures. The size of each signatures is constant, and the verification cost decreases with each new signature, becoming more efficient as the number of signatures grows.

I've been working on some new (hash-based) post-quantum signature schemes:

Unbalanced Winternitz Signatures (pdf)

Abstract: We introduce 'uwots' (unbalanced Winternitz one-time signatures): an optimized, tweakable generalization of the Winternitz signature scheme.

Integer Composition Signatures (pdf)

Abstract: We introduce integer composition signatures (ic): a hash-based family of one-time signatures. The family shows improvements over previous schemes like Winternitz: less costly/shorter signatures, verification in constant time, and tweakable parameters allowing optimization for either signing/verifying.

Code

Jotasapiens OTS: ic, icvar, uwots v4 - sha256 754a600b4cef06d5c773440eb9ed1bc0e3ce208827399703ededd833a141a0fc

Edit: We are migrating servers and the code is not available at this time. The download link will be back soon. In the meanwhile, feel free to contact me, and i'll gladly send you a copy of the code.

Edit: the code is back online. It can be download from: