Threshold signatures

Threshold signatures allow a required number of participants to cooperate in producing a digital signature using shares of a common signing key. In cryptocurrency custody, this can distribute signing authority across systems or organizations. A threshold arrangement depends on its cryptographic protocol and key-management design; the label MPC wallet does not specify those details.

Thresholds and multisignatures

In a threshold scheme, a sufficient subset of participants can sign. FROST is a two-round Schnorr threshold-signing protocol, with security assumptions about key-share generation and the number of corrupted participants. RFC 9591 is an informational Crypto Forum Research Group publication, not an Internet Standards Track specification.

Multiple-party signing does not always mean threshold signing. MuSig2, specified by BIP 327, aggregates participants' public keys and produces a BIP 340-compatible Schnorr signature, but requires every signer involved in key aggregation. It is an n-of-n multisignature scheme, rather than a t-of-n threshold scheme.

Security and operational assumptions

Distributing shares changes the trust model; it does not remove the need for secure systems. FROST assumes secure generation and distribution of shares and limits on how many participants an adversary can corrupt. Its security considerations address nonce reuse, side channels and protocol failures. Signing availability and protection against forgery are separate properties.

Custody services

Google Cloud's Multi-party Compute documentation, checked in October 2026, describes a custody platform combining threshold signing with organizational controls. The documentation labels the service Preview and describes a v1beta API. It lists ECDSA over secp256k1 for Bitcoin and EVM-compatible applications; this should not be read as a claim of support for every blockchain signature format.

Cryptographic authorization also differs from transaction-policy automation. Google's policy documentation says enough signers can authorize a transaction that automated policies deny. A policy verdict therefore has to be understood within the service's signer and governance model.