KarpelesLab / libwallet / 24823904957

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wltwallet: Wallet:promote — reshare imported share into TSS committee

The complement to importPrivateKey / importMnemonic: convert a 1-of-1
imported wallet (Schema "raw" or "mnemonic") into a normal N-of-T TSS
wallet via tss-lib's resharing protocol. The master pubkey and chaincode
are preserved — the wallet's address does NOT change — only the
storage of the signing key changes from "single share, full privkey"
to "M shares with T-threshold reconstruction".

Mechanism:

  1. Decrypt the imported share via the Old KeyDescription (typically
     the password the user set at import time). For mnemonic imports
     this also runs BIP39 PBKDF2 + BIP32/SLIP-0010 master derivation
     to recover the master privkey.

  2. Synthesize a 1-of-1 ecdsatss.Key with Xi = master privkey,
     ECDSAPub = master pubkey. NTildej / H1j / H2j / PaillierPKs are
     left nil — they're only consumed when the party will SIGN, and
     the imported share's only role here is to shard out via VSS in
     round 1.

  3. Allocate the New committee's WalletKey rows with fresh Paillier
     pre-params (the slow safe-prime generation that
     wallet.go:initializeWallet runs).

  4. Run ecdsatss.NewResharing with old=(N=1, T=0) and
     new=(N=len(New), T=Threshold). Local TssHub wires both committees
     since the imported wallet has no remote peers (it was 1-of-1).

  5. Encrypt and persist the new shares; ForceDelete the imported
     WalletKey row; bump w.Threshold to the new value. The Wallet
     row's Pubkey + Chaincode are unchanged.

Validation:

  - Wallet must be 1-of-1 imported (asserts len(Keys)==1, Schema in
    {"raw","mnemonic"}).
  - secp256k1 only in this commit; ed25519 promote (eddsatss
    equivalent) is a follow-up.
  - len(New) >= 2 and 1 <= Threshold < len(New).

Dart client (wallet_api.dart):

  client.wallets.promote(walletId,
      oldKeys: [...], newKeys: [...], threshold: 2)

Same shape as the existing wallets.reshare(...) but with explicit
Threshold... (continued)

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