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feat(sdk-lib-mpc): combine partial signatures util support
Ticket: HSM-341
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Original file line number | Diff line number | Diff line change |
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import { Signature } from '@noble/secp256k1'; | ||
import { Secp256k1Curve } from '../../curves'; | ||
import { bigIntFromBufferBE, bigIntToBufferBE } from '../../util'; | ||
import { DklsSignature } from './types'; | ||
import { decode } from 'cbor'; | ||
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/** | ||
* Combines partial signatures from parties participating in DSG. | ||
* @param round4MessagePayloads - round 4 message payloads from participating parties | ||
* @param rHex - hex representation of the r value in the signature | ||
* @returns {DeserializedMessages} - messages to send to other parties for the next round | ||
*/ | ||
export function combinePartialSignatures(round4MessagePayloads: Uint8Array[], rHex: string): DklsSignature { | ||
const r = bigIntFromBufferBE(Buffer.from(rHex, 'hex').subarray(1)); | ||
const s0Arr = round4MessagePayloads.map((p) => decode(p).s_0); | ||
const s1Arr = round4MessagePayloads.map((p) => decode(p).s_1); | ||
const s0BigInts = s0Arr.map((s0) => bigIntFromBufferBE(Buffer.from(s0))); | ||
const s1BigInts = s1Arr.map((s1) => bigIntFromBufferBE(Buffer.from(s1))); | ||
const secp256k1Curve = new Secp256k1Curve(); | ||
const s0Sum = s0BigInts.slice(1).reduce((sumSoFar, s0) => secp256k1Curve.scalarAdd(sumSoFar, s0), s0BigInts[0]); | ||
const s1Sum = s1BigInts.slice(1).reduce((sumSoFar, s1) => secp256k1Curve.scalarAdd(sumSoFar, s1), s1BigInts[0]); | ||
const s = secp256k1Curve.scalarMult(s0Sum, secp256k1Curve.scalarInvert(s1Sum)); | ||
const sig = new Signature(r, s); | ||
const normalizedSig = sig.normalizeS(); | ||
return { | ||
R: new Uint8Array(bigIntToBufferBE(normalizedSig.r)), | ||
S: new Uint8Array(bigIntToBufferBE(normalizedSig.s)), | ||
}; | ||
} |
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