The secret spend key is kept encrypted in memory, and
decrypted on the fly when needed.
Both spend and view secret keys are kept encrypted in a JSON
field in the keys file. This avoids leaving the keys in
memory due to being manipulated by the JSON I/O API.
This is based on how much an attacking miner stands to lose in block
rewardy by mining a private chain which double spends a payment.
This is not foolproof, since mining is based on luck, and breaks
down as the attacking miner nears 50% of the network hash rate,
and the estimation is based on a constant block reward.
for privacy reasons, so an untrusted node can't easily track
wallets from IP address to IP address, etc. The granularity
is 1024 blocks, which is about a day and a half.
a99ef176 wallet-rpc: take subaddress account as arg for get_transfer_by_txid (stoffu)
77125096 wallet-rpc: rename *_INDEX_OUTOFBOUND into *_INDEX_OUT_OF_BOUNDS (stoffu)
f90c76be Return appropriate error code when there's no connection to daemon (Michał Sałaban)
3cb65b3f Return appropriate error code when not enough money for tx (Michał Sałaban)
9996d5e9 wallet2: guard against the dameon sending blocks before last checkpoint (moneromooo-monero)
eadaa6aa wallet_rpc_server: fix wallet leak on error exit (moneromooo-monero)
bd5cce07 network_throttle: fix ineffective locking (moneromooo-monero)
e0a61299 network_throttle: remove unused xxx static member (moneromooo-monero)
24f584d9 cryptonote_core: remove unused functions with off by one bugs (moneromooo-monero)
b1634aa3 blockchain: don't leave dangling pointers in this (moneromooo-monero)
8e60b81c cryptonote_core: fix db leak on error (moneromooo-monero)
213e326c abstract_tcp_server2: log init_server errors as fatal (moneromooo-monero)
b51dc566 use const refs in for loops for non tiny types (moneromooo-monero)
f0568ca6 net_parse_helpers: fix regex error checking (moneromooo-monero)
b49ddc76 check accessing an element past the end of a container (moneromooo-monero)
2305bf26 check return value for generate_key_derivation and derive_public_key (moneromooo-monero)
a4240d9f catch const exceptions (moneromooo-monero)
45a1c4c0 add empty container sanity checks when using front() and back() (moneromooo-monero)
56fa6ce1 tests: fix a buffer overread in a unit test (moneromooo-monero)
b4524892 rpc: guard against json parsing a non object (moneromooo-monero)
c2ed8618 easylogging++: avoid buffer underflow (moneromooo-monero)
187a6ab2 epee: trap failure to parse URI from request (moneromooo-monero)
061789b5 checkpoints: trap failure to load JSON checkpoints (moneromooo-monero)
ba2fefb9 checkpoints: pass std::string by const ref, not const value (moneromooo-monero)
38c8f4e0 mlog: terminate a string at last char, just in case (moneromooo-monero)
d753d716 fix a few leaks by throwing objects, not newed pointers to objects (moneromooo-monero)
fe568db8 p2p: use size_t for arbitrary counters instead of uint8_t (moneromooo-monero)
46d6fa35 cryptonote_protocol: sanity check chain hashes from peer (moneromooo-monero)
25584f86 cryptonote_protocol: print peer versions when unexpected (moneromooo-monero)
490a5d41 rpc: do not try to use an invalid txid in relay_tx (moneromooo-monero)
Scheme by luigi1111:
Multisig for RingCT on Monero
2 of 2
User A (coordinator):
Spendkey b,B
Viewkey a,A (shared)
User B:
Spendkey c,C
Viewkey a,A (shared)
Public Address: C+B, A
Both have their own watch only wallet via C+B, a
A will coordinate spending process (though B could easily as well, coordinator is more needed for more participants)
A and B watch for incoming outputs
B creates "half" key images for discovered output D:
I2_D = (Hs(aR)+c) * Hp(D)
B also creates 1.5 random keypairs (one scalar and 2 pubkeys; one on base G and one on base Hp(D)) for each output, storing the scalar(k) (linked to D),
and sending the pubkeys with I2_D.
A also creates "half" key images:
I1_D = (Hs(aR)+b) * Hp(D)
Then I_D = I1_D + I2_D
Having I_D allows A to check spent status of course, but more importantly allows A to actually build a transaction prefix (and thus transaction).
A builds the transaction until most of the way through MLSAG_Gen, adding the 2 pubkeys (per input) provided with I2_D
to his own generated ones where they are needed (secret row L, R).
At this point, A has a mostly completed transaction (but with an invalid/incomplete signature). A sends over the tx and includes r,
which allows B (with the recipient's address) to verify the destination and amount (by reconstructing the stealth address and decoding ecdhInfo).
B then finishes the signature by computing ss[secret_index][0] = ss[secret_index][0] + k - cc[secret_index]*c (secret indices need to be passed as well).
B can then broadcast the tx, or send it back to A for broadcasting. Once B has completed the signing (and verified the tx to be valid), he can add the full I_D
to his cache, allowing him to verify spent status as well.
NOTE:
A and B *must* present key A and B to each other with a valid signature proving they know a and b respectively.
Otherwise, trickery like the following becomes possible:
A creates viewkey a,A, spendkey b,B, and sends a,A,B to B.
B creates a fake key C = zG - B. B sends C back to A.
The combined spendkey C+B then equals zG, allowing B to spend funds at any time!
The signature fixes this, because B does not know a c corresponding to C (and thus can't produce a signature).
2 of 3
User A (coordinator)
Shared viewkey a,A
"spendkey" j,J
User B
"spendkey" k,K
User C
"spendkey" m,M
A collects K and M from B and C
B collects J and M from A and C
C collects J and K from A and B
A computes N = nG, n = Hs(jK)
A computes O = oG, o = Hs(jM)
B anc C compute P = pG, p = Hs(kM) || Hs(mK)
B and C can also compute N and O respectively if they wish to be able to coordinate
Address: N+O+P, A
The rest follows as above. The coordinator possesses 2 of 3 needed keys; he can get the other
needed part of the signature/key images from either of the other two.
Alternatively, if secure communication exists between parties:
A gives j to B
B gives k to C
C gives m to A
Address: J+K+M, A
3 of 3
Identical to 2 of 2, except the coordinator must collect the key images from both of the others.
The transaction must also be passed an additional hop: A -> B -> C (or A -> C -> B), who can then broadcast it
or send it back to A.
N-1 of N
Generally the same as 2 of 3, except participants need to be arranged in a ring to pass their keys around
(using either the secure or insecure method).
For example (ignoring viewkey so letters line up):
[4 of 5]
User: spendkey
A: a
B: b
C: c
D: d
E: e
a -> B, b -> C, c -> D, d -> E, e -> A
Order of signing does not matter, it just must reach n-1 users. A "remaining keys" list must be passed around with
the transaction so the signers know if they should use 1 or both keys.
Collecting key image parts becomes a little messy, but basically every wallet sends over both of their parts with a tag for each.
Thia way the coordinating wallet can keep track of which images have been added and which wallet they come from. Reasoning:
1. The key images must be added only once (coordinator will get key images for key a from both A and B, he must add only one to get the proper key actual key image)
2. The coordinator must keep track of which helper pubkeys came from which wallet (discussed in 2 of 2 section). The coordinator
must choose only one set to use, then include his choice in the "remaining keys" list so the other wallets know which of their keys to use.
You can generalize it further to N-2 of N or even M of N, but I'm not sure there's legitimate demand to justify the complexity. It might
also be straightforward enough to support with minimal changes from N-1 format.
You basically just give each user additional keys for each additional "-1" you desire. N-2 would be 3 keys per user, N-3 4 keys, etc.
The process is somewhat cumbersome:
To create a N/N multisig wallet:
- each participant creates a normal wallet
- each participant runs "prepare_multisig", and sends the resulting string to every other participant
- each participant runs "make_multisig N A B C D...", with N being the threshold and A B C D... being the strings received from other participants (the threshold must currently equal N)
As txes are received, participants' wallets will need to synchronize so that those new outputs may be spent:
- each participant runs "export_multisig FILENAME", and sends the FILENAME file to every other participant
- each participant runs "import_multisig A B C D...", with A B C D... being the filenames received from other participants
Then, a transaction may be initiated:
- one of the participants runs "transfer ADDRESS AMOUNT"
- this partly signed transaction will be written to the "multisig_monero_tx" file
- the initiator sends this file to another participant
- that other participant runs "sign_multisig multisig_monero_tx"
- the resulting transaction is written to the "multisig_monero_tx" file again
- if the threshold was not reached, the file must be sent to another participant, until enough have signed
- the last participant to sign runs "submit_multisig multisig_monero_tx" to relay the transaction to the Monero network
9739da1e wallet_rpc_server: new relay_tx command (moneromooo-monero)
01dc8297 wallet: transfer RPC can now return tx metadata (pending_tx) (moneromooo-monero)
83fa9047 serialization: add std::set and std::unordered_set serialization (moneromooo-monero)
- refactoring: proof generation/checking code was moved from simplewallet.cpp to wallet2.cpp
- allow an arbitrary message to be signed together with txid
- introduce two types (outbound & inbound) of tx proofs; with the same syntax, inbound is selected when <address> belongs to this wallet, outbound otherwise. see GitHub thread for more discussion
- wallet RPC: added get_tx_key, check_tx_key, get_tx_proof, check_tx_proof
- wallet API: moved WalletManagerImpl::checkPayment to Wallet::checkTxKey, added Wallet::getTxProof/checkTxProof
- get_tx_key/check_tx_key: handle additional tx keys by concatenating them into a single string
