Paper 2020/1244

Taming the many EdDSAs

Konstantinos Chalkias, François Garillot, and Valeria Nikolaenko


This paper analyses security of concrete instantiations of EdDSA by identifying exploitable inconsistencies between standardization recommendations and Ed25519 implementations. We mainly focus on current ambiguity regarding signature verification equations, binding and malleability guarantees, and incompatibilities between randomized batch and single verification. We give a formulation of Ed25519 signature scheme that achieves the highest level of security, explaining how each step of the algorithm links with the formal security properties. We develop optimizations to allow for more efficient secure implementations. Finally, we designed a set of edge-case test-vectors and run them by some of the most popular Ed25519 libraries. The results allowed to understand the security level of those implementations and showed that most libraries do not comply with the latest standardization recommendations. The methodology allows to test compatibility of different Ed25519 implementations which is of practical importance for consensus-driven applications.

Note: Submitted to SSR conference on Aug 31, 2020. Accepted to SSR conference on Oct 1, 2020.

Available format(s)
Public-key cryptography
Publication info
Published elsewhere. Minor revision. Security Standardisation Research Conference (SSR 2020)
Contact author(s)
valerini @ fb com
kostascrypto @ fb com
valeria nikolaenko @ gmail com
francois @ garillot net
2021-12-02: last of 5 revisions
2020-10-09: received
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Creative Commons Attribution


      author = {Konstantinos Chalkias and François Garillot and Valeria Nikolaenko},
      title = {Taming the many {EdDSAs}},
      howpublished = {Cryptology ePrint Archive, Paper 2020/1244},
      year = {2020},
      doi = {10.1007/978-3-030-64357-7_4},
      note = {\url{}},
      url = {}
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