Paper 2022/1296

Efficient Asymmetric Threshold ECDSA for MPC-based Cold Storage

Constantin Blokh, Fireblocks
Nikolaos Makriyannis, Fireblocks
Udi Peled, Fireblocks

Motivated by applications to cold-storage solutions for ECDSA-based cryptocurrencies, we present a new threshold ECDSA protocol between $n$ ``online'' parties and a single ``offline'' (aka.~cold) party. The primary objective of this protocol is to minimize the exposure of the offline party in terms of connected time and bandwidth. This is achieved through a unique asymmetric signing phase, in which the majority of computation, communication, and interaction is handled by the online parties. Our protocol supports a very efficient non-interactive pre-signing stage; the parties calculate preprocessed data for future signatures where each party (offline or online) sends a single independently-generated short message per future signature. Then, to calculate the signature, the offline party simply receives a single short message (approx.~300B) and outputs the signature. All previous ECDSA protocols either have high exposure for all parties, or rely on non-standard coding assumptions. (We assume strong RSA, DCR, DDH and enhanced unforgeability of ECDSA.) To achieve the above, we present a new batching technique for proving in zero-knowledge that the plaintexts of practically any number of Paillier ciphertexts all lie in a given range. The cost of the resulting batch proof is very close to that of the non-batch proof for a single ciphertext, and the technique is applicable to arbitrary Schnorr-style protocols.

Note: The present version introduces a simplified variant of the core two-party protocol and provides the corresponding security analysis, serving as an introductory example (see Section 4). Additionally, the paper has been further revised for conciseness.

Available format(s)
Cryptographic protocols
Publication info
ECDSAThreshold SignaturesMPCUCAdaptive AdversariesMalicious AdversariesBatchingCold StorageBlockchain
Contact author(s)
n makriyannis @ gmail com
2023-10-07: last of 6 revisions
2022-09-29: received
See all versions
Short URL
Creative Commons Attribution


      author = {Constantin Blokh and Nikolaos Makriyannis and Udi Peled},
      title = {Efficient Asymmetric Threshold {ECDSA} for {MPC}-based Cold Storage},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1296},
      year = {2022},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.