Shamir Secret Sharing (SSS): SSS divides a secret, e.g. a private key, into multiple "shares" using polynomial interpolation. A minimum threshold of shares is required to reconstruct the original secret, while each share reveals no information on its own. This makes SSS an excellent solution for securing assets like encrypted data backups, password recovery systems, or cold storage for digital assets. ****While effective for data backups, SSS can risk compromisation during key generation before the secret is split and distributed.

MPC Threshold Signature Scheme (MPC-TSS): MPC-TSS is a cryptographic approach that allows multiple parties to collaboratively sign transactions or perform cryptographic operations without ever assembling the full private key. Each participant holds a share of the key, and these shares collectively generate a valid signature while keeping the private key decentralized and secure. By eliminating the risk of key exposure, MPC-TSS has become the industry standard for securing institutional crypto assets, offering robust protection against potential breaches.

• Threshold ECDSA or EdDSA

  • The private key sk is split into n shares using techniques like Shamir's Secret Sharing (SSS) or other secret sharing schemes.
  • These shares are distributed to n parties, such that any subset of t out of n can produce a valid signature (t-out-of-n threshold).

• Store MPC key shares in Hardware Security Modules (HSMs), providing enterprise-grade protection and ensuring robust safeguards for institutional crypto assets

• Privy uses SSS (now acquired by Stripe)

• Honest majority assumption - so large threshold is better

• MPC is very chatty - scale issues?

  • MPC signing requires multiple rounds of communication between parties to compute nonces and partial signatures, making it latency-sensitive and bandwidth-heavy.

MPC TSS technical details

1. What allows it to sign transactions without ever assembling the full key?
2. Why is the protocol considered chatty , and I have heard this communication heavy protocol limits it scale. Explain
3. Who are the main companies that use MPC TSS and what kind of use cases they work on
4. What is the state of the art for MPC TSS, which algorithm is the industry standard today
   1. For Threshold ECDSA (used in Bitcoin, Ethereum, etc.):
   • GG18 (Gennaro & Goldfeder, 2018): First practical t-of-n ECDSA.
   • GG20: Improved round complexity, more robust (better pre-processing).
   • FROST (Flexible Round-Optimized Schnorr Threshold signatures):
     • Schnorr-based (used in Taproot, modern L1s)
     • Fewer rounds, more scalable
     • Gaining adoption as networks adopt Schnorr over ECDSA
   • DKLS, Lindell, CGGMP21, etc.
   • Threshold EdDSA (Ed25519) – used in Solana, Cosmos. Fewer rounds than ECDSA.
   • FROST + DKG (Distributed Key Gen): emerging standard in decentralized identity, validator orchestration, and ZK signer networks. FROST is the preferred direction for newer systems due to better performance.
5. What are the main GTM challenges for an MPC solution?
   • Education barrier
     • MPC is cryptographically complex.
     • Most enterprise buyers don’t understand the difference between MPC, HSMs, and multisig.
     • Requires technical pre-sales and strong developer documentation.
   • Integration complexity
     • SDKs must support a wide range of blockchains and signing schemes.
     • Complex coordination for mobile apps, enclave support, or co-signers.
     • Need for policy engines (e.g., travel rules, AML) to sit on top of MPC.
   • Latency & UX
     • Real-time signing can feel sluggish if multiple parties or geographies are involved.
     • Businesses with high TPS (exchanges, MM) need speed + security, not just security.
   • Vendor lock-in fears
     • Enterprises are wary of being locked into proprietary MPC implementations.
     • Open standards like FROST are helping, but audited open-source MPC libs are still rare.

1. Key generation Steps