Two-party ECDSA with JavaCard-based smartcards
| Authors | |
|---|---|
| Year of publication | 2025 |
| Type | Article in Proceedings |
| Conference | Applied Cryptography and Network Security: 23rd International Conference on Applied Cryptography and Network Security |
| MU Faculty or unit | |
| Citation | |
| web | https://link.springer.com/chapter/10.1007/978-3-031-95764-2_7 |
| Doi | http://dx.doi.org/10.1007/978-3-031-95764-2_7 |
| Keywords | Smartcards;Two-party ECDSA;Threshold cryptography |
| Description | Threshold signatures are an effective method for enhancing the security of signing keys based on distributing their storage across multiple devices and enabling direct signing using the produced key shares without reconstructing the original keys. For instance, a private key can be split between a smartphone and a smartcard, with each device controlling a key share. To create a signature, a user simply taps the smartcard on the smartphone, executing the threshold signing protocol over the contactless interface, which results in the signature. However, computing threshold signatures on smartcards presents significant challenges due to their limited computational resources. This issue becomes even more pronounced with ECDSA signatures, the most widely used type of elliptic-curve-based signatures. Unlike other common EC-based signature schemes, threshold ECDSA is computationally intensive because it requires the multiplication of secretly shared values. To address this challenge, we surveyed protocols for computing threshold ECDSA signatures and proposed three approaches viable for computation on current smartcards with different trade-offs. The first approach is based on a two-party protocol by Lindell [22], which is computable on smartcards thanks to their modular exponentiation coprocessor but still relatively slow. The remaining two approaches utilize the preprocessing model with an optional trusted preprocessing party. We implemented all three approaches for the JavaCard platform while considering the hardware constraints and evaluated their performance on a physical smartcard to assess their practicality. |
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