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
Partially implements #74.
Securely erases keys from memory after they are no longer needed. Might have a
performance impact, which I haven't measured (perf measurements aren't
generally reliable on laptops).
Thanks to @stoffu for the suggestion to specialize the pod_to_hex/hex_to_pod
functions. Using overloads + SFINAE instead generalizes it so other types can
be marked as scrubbed without adding more boilerplate.
3dffe71b new wipeable_string class to replace std::string passphrases (moneromooo-monero)
7a2a5741 utils: initialize easylogging++ in on_startup (moneromooo-monero)
54950829 use memwipe in a few relevant places (moneromooo-monero)
000666ff add a memwipe function (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
0d9c0db9 Do not build against epee_readline if it was not built (Howard Chu)
178014c9 split off readline code into epee_readline (moneromooo-monero)
a9e14a19 link against readline only for monerod and wallet-wallet-{rpc,cli} (moneromooo-monero)
437421ce wallet: move some scoped_message_writer calls from the libs (moneromooo-monero)
e89994e9 wallet: rejig to avoid prompting in wallet2 (moneromooo-monero)
ec5135e5 move input_line from command_line to simplewallet (moneromooo-monero)
082db75f move cryptonote command line options to cryptonote_core (moneromooo-monero)
wallet2 is a library, and should not prompt for stdin. Instead,
pass a function so simplewallet can prompt on stdin, and a GUI
might display a window, etc.
Transactions in the txpool are marked when another transaction
is seen double spending one or more of its inputs.
This is then exposed wherever appropriate.
Note that being marked with this "double spend seen" flag does
NOT mean this transaction IS a double spend and will never be
mined: it just means that the network has seen at least another
transaction spending at least one of the same inputs, so care
should be taken to wait for a few confirmations before acting
upon that transaction (ie, mostly of use for merchants wanting
to accept unconfirmed transactions).
d0463312 fix libwallet api test after api change (Jaquee)
a46c1eed Wallet2: Don't throw when subaddress label doesn't exist (Jaquee)
086b7db2 Wallet API: default values for account and subaddr index (Jaquee)
Lack of it results in `m_refresh_from_block_height` being < 0 (18446744...) on low heights, which blocks `process_new_blockchain_entry` and never process coins on heights less than blocks_per_month.
Follow-up to #2258
a15e8583 wallet2: guard against daemon sending txes in the wrong order (moneromooo-monero)
8fe5f609 rpc: order transactions in the order they were requested (moneromooo-monero)
d58700e0 WalletAPI: only allow trusted daemon when importing key images (Jaquee)
8a9bbd26 WalletAPI: copy wallet data when creating a view only wallet (Jaquee)
d27fe32e wallet2: export/import wallet data functions (Jaquee)
225a25f3 import_key_images - allow importing without being connected to daemon (Jaquee)
b7d6ec83 simplewallet: add (out of sync) or (no daemon) markers in the prompt (moneromooo-monero)
fa23a500 wallet2: add a is_synced function (moneromooo-monero)
f1307bbd node_rpc_proxy: add a proxy for target height (moneromooo-monero)
When scanning the txpool without having first updated the
blockchain, the tx would be seen as neither in the txpool
nor the chain, and removed, so it'd only reappear once the
chain is refreshed, and the tx seen in a block.
If the refresh height is in the future, the current code will
loop till the actual height reaches this. Fix it by bailing out
if we receive only three hashes, which is what we set in the
call parameters.
The previous patch was based on a wrong premise (that the
daemon height was 0 because the daemon calling code wasn't
yet initialized). In fact, current height approximation
was not setup for testnet. Fix this.
e2529347 Correct spelling of 'get_upper_transaction_size_limit' (Nano Akron)
3029d0ef Remove the 1.25x multiplier in max transaction size in just the wallet (Nano Akron)
It sweeps all outputs below the given threshold
This is available via the existing sweep_all RPC, by setting
amount_threshold the desired amount (in atomic units)
a6d5bb75 wallet2: refer to triangular distribution for recent zone in comment (moneromooo-monero)
ac1aba90 wallet2: bias fake outs more towards recent outputs (moneromooo-monero)
It was wrongly refering to equiprobable distribution, which I think
I'd originally done, but forgot to update the comment after changing
to triangular
Reported by smooth on IRC
Two recent papers quantified the real usage bias for the
real output in a ring being the true one, and shows that
the current biasing is much too weak.
While we wait for a better solution, we increase the ratio
of recent-to-total fake outputs, as well as decrease the
time window for recent outputs, so that half the fake outs
are selected within the last 1.8 day. Value plucked from
figure 10, page 11 of An Empirical Analysis of Linkability
in the Monero Blockchain, 2017, Miller et al.
This is also arbitrary, of course, but serves as a stopgap
till a better selection algorithm is chosen.
If using a large input and many destinations, the code would
generate as many outputs as it could using that input, even if
it would bring the resulting tx above the max tx size.
With the change from the original transfer method to the new
algorithm, payments to the same destination were merged. It
seemed like a good idea, optimizing space. However, it is a
useful tool for people who want to split large outputs into
several smaller ones (ie, service providers making frequent
payments, and who do not like a large chunk of their balance
being locked for 10 blocks after each payment).
Default to off, which is a change from the previous behavior.
When a single input is enough to satisfy a transfer, the code would
previously try to add a second input, to match the "canonical" makeup
of a transaction with two inputs and two outputs. This would cause
wallets to slowly merge outputs till all the monero ends up in a
single output, which causes trouble when making two transactions
one after the other, since change is locked for 10 blocks, and an
increasing portion of the remaining balance would end up locked on
each transaction.
There are two new settings (min-output-count and min-output-value)
which can control when to stop adding such unneeded second outputs.
The idea is that small "dust" outputs will still get added, but
larger ones will not.
Enable with, eg:
set min-output-count 10
set min-output-value 30
to avoid using an unneeded second output of 30 monero or more, if
there would be less than 10 such outputs left.
This does not invalidate any other reason why such outputs would
be used (ie, when they're really needed to satisfy a transfer, or
when randomly picked in the normal course of selection). This may
be improved in the future.
Asking for a full histogram from a remote node (since it's
untrusted) is pretty slow, and spams the remote node, so
we replace it by only adding a second input if we have rct
ones, which are for all intents and purposes always mixable.
Minimum mixin 4 and enforced ringct is moved from v5 to v6.
v5 is now used for an increased minimum block size (from 60000
to 300000) to cater for larger typical/minimum transaction size.
The fee algorithm is also changed to decrease the base per kB
fee, and add a cheap tier for those transactions which we do
not care if they get delayed (or even included in a block).
This reverts commit d47dac9a88.
Callers actually expect the key to be payment id, so this
needs a lot more changes (like storing payment ids in the
structure, and possibly also to other existing structures
which do the same thing).
A relatedness check was meant to be done in the case of adding
an extra output if just one was enough. This was mistakenly
added to the "preferred output" case.
c02e1cb9 Updates to epee HTTP client code - http_simple_client now uses std::chrono for timeouts - http_simple_client accepts timeouts per connect / invoke call - shortened names of epee http invoke functions - invoke command functions only take relative path, connection is not automatically performed (Lee Clagett)
If a rct transaction can be made with just one input, a second
output will be added. This output will be the smallest amount
output available. However, if this output is a non rct output
with less available fake outs than requested, the transaction
will be rejected. We now check the histogram to only consider
outputs with enough available fake outs in the first place.
These warnings were emitted by clang++, and they are real bugs.
src/rpc/core_rpc_server.cpp:208:58: warning: adding 'uint64_t'
(aka 'unsigned long') to a string does not append to the string
[-Wstring-plus-int]
res.status = "Error retrieving block at height " + height;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
The obvious intent is achieved by using std::to_string().
- http_simple_client now uses std::chrono for timeouts
- http_simple_client accepts timeouts per connect / invoke call
- shortened names of epee http invoke functions
- invoke command functions only take relative path, connection
is not automatically performed
This would have tried to send a second output to make the tx
look like the 2/2 ideal, but it would not fail to find one
because picking an output from preferred_inputs priority list
did not remove it from the unused tranfer/dust outputs, so
it would try to send the same output twice.
While there, I also added a check to avoid sending a second
input if it's related to the first. Better 1/2 than linking
inputs, I think.
This avoids indirectly leaking the real output to the daemon,
and is faster.
This will still happen for more complex cases, especially
when cancelling a tx and "re-rolling" it.
This replaces the epee and data_loggers logging systems with
a single one, and also adds filename:line and explicit severity
levels. Categories may be defined, and logging severity set
by category (or set of categories). epee style 0-4 log level
maps to a sensible severity configuration. Log files now also
rotate when reaching 100 MB.
To select which logs to output, use the MONERO_LOGS environment
variable, with a comma separated list of categories (globs are
supported), with their requested severity level after a colon.
If a log matches more than one such setting, the last one in
the configuration string applies. A few examples:
This one is (mostly) silent, only outputting fatal errors:
MONERO_LOGS=*:FATAL
This one is very verbose:
MONERO_LOGS=*:TRACE
This one is totally silent (logwise):
MONERO_LOGS=""
This one outputs all errors and warnings, except for the
"verify" category, which prints just fatal errors (the verify
category is used for logs about incoming transactions and
blocks, and it is expected that some/many will fail to verify,
hence we don't want the spam):
MONERO_LOGS=*:WARNING,verify:FATAL
Log levels are, in decreasing order of priority:
FATAL, ERROR, WARNING, INFO, DEBUG, TRACE
Subcategories may be added using prefixes and globs. This
example will output net.p2p logs at the TRACE level, but all
other net* logs only at INFO:
MONERO_LOGS=*:ERROR,net*:INFO,net.p2p:TRACE
Logs which are intended for the user (which Monero was using
a lot through epee, but really isn't a nice way to go things)
should use the "global" category. There are a few helper macros
for using this category, eg: MGINFO("this shows up by default")
or MGINFO_RED("this is red"), to try to keep a similar look
and feel for now.
Existing epee log macros still exist, and map to the new log
levels, but since they're used as a "user facing" UI element
as much as a logging system, they often don't map well to log
severities (ie, a log level 0 log may be an error, or may be
something we want the user to see, such as an important info).
In those cases, I tried to use the new macros. In other cases,
I left the existing macros in. When modifying logs, it is
probably best to switch to the new macros with explicit levels.
The --log-level options and set_log commands now also accept
category settings, in addition to the epee style log levels.
If we'd make a rct tx with just one input, we try to add
a second one to match the 2/2 ideal. This means more txes
use that template (and are thus using a larger anonymity
set), and it coalesces outputs "for free". We use the
smallest amount outputs in priority for this, so we can
"clean" the wallet at the same time.
