TSS

Silent Shard has been built using a cryptographic base of Multiparty computation (MPC). MPC enables a set of parties that do not trust each other to try to jointly compute a function (digital signature generation in this case) over their inputs (key shards in this case) while keeping those inputs privately stored with them. Threshold signatures are a case enabled by multiparty computation where a threshold number of parties, out of the previously agreed group of approving (participating) nodes, can compute a cryptographic digital signature. ECDSA is one type of such a signature scheme based on elliptic curves.

A visual representation of an MPC TSS protocol

Threshold Signatures (TSS) scheme protocols are multi-step and interactive protocols built through cryptographic primitives and zero-knowledge proofs to generate an indistinguishable signature as generated by a wallet holding the private key in one place.

TSS consists of three stages:

• Distributed Key Generation (DKG),

• Distributed Signature Generation, and

• Proactive Security with Key rotation/refresh.

These functions involve cryptographic computing at the participating nodes of the MPC quorum and exchanges of rounds of messages which ultimately lead to the generation of a valid signature at the requested node. These computing nodes can be any device with sufficient computational and memory capability, including but not limited to smartphones, server nodes, and edge devices. The basic philosophy behind Silent Shard remains that no single device holding the private key can be used to generate signatures and move digital assets. The private key is shared among multiple computing nodes so that no party has any information about the key.

Then, in order to generate a signature, the threshold number of devices run a secure two-party computation protocol that generates the signature without revealing anything about the parties' key shares to each other. These devices may or may not be associated with the same person or organization and can be any form factor. Thus, one could use this to create a wallet, sharing the private key between one's mobile and one's laptop, between one's mobile and a VM in the cloud, and so on.