Signatures¶
Signature Structure¶
To interact with the system, users have to send messages containing orders they wish to execute. The following order types are currently supported:
Trade order, declaring intent to sell a certain amount of a certain token in exchange for a different token at a certain ratio.
Transfer order, requesting funds to be transferred from one vault to another.
The order data is sent directly to the exchange through an interface exposed there, in addition to a signature over all its fields that is verified by the proof system.
The signature is constructed as follows:
\(H\) is the Pedersen hash function, \(k_{private}\) is the user’s private key, and the words \(w_1\), \(w_2\) and \(w_3\) are three \(256\)-bit words containing the data required for the signature, as described below.
Message Word Definition¶
\(w_1\) is the token ID to be sold (or transferred).
\(w_2\) depends on the order type:
In a trade order, \(w_2\) is the token ID to be bought.
In a transfer order, \(w_2\) is the transfer target’s public key.
\(w_3\) is a bit-packed message whose lower 245 bits conform to the format described below, depending on the order type.
+---+---------+---------+-------------------+-------------------+---------+-------+
#bits | 4 | 31 | 31 | 63 | 63 | 31 | 22 |
+---+---------+---------+-------------------+-------------------+---------+-------+
label A B C D E F G
Where:
A: the order type, 0 for trade order or 1 for transfer order.
B: the ID of the vault from which the user wants to take funds.
C:
In case of a trade order, the ID of the vault into which the user wants to receive funds.
In case of a transfer order, the ID of the vault to receive the transfered funds.
D: the amount to be sold / transfered.
E: the amount to buy in exchange (0 in case of a transfer order).
F: A nonce for the transaction.
G: the expiration timestamp, in hours since the Unix epoch. For example, for the order to expire 24 hours from the beginning of the current hour, set the timestamp to \(\left\lfloor{\frac{t_{unix}}{3600}}\right\rfloor + 24\).
Examples¶
Suppose Alice and Bob are two users trading tokens X (whose ID is 100) and Y (whose ID is 200), with the following setup:
Transfer Example¶
Suppose that Alice wants to transfer \(25X\) from her vault with ID 7 to Bob’s vault with ID 12. In this case she will sign the following message:
Where \(m\) is formatted as follows
+---+---------+---------+-------------------+-------------------+-----------+-------+
value | 1 | 7 | 12 | 25 | 0 | nonce | ts |
+---+---------+---------+-------------------+-------------------+-----------+-------+
label A B C D E F G
Order Example¶
Suppose that now Alice wants to trade \(9000X\) from her vault with ID 7 for \(15000Y\), to be deposited in her vault with ID 4 if the trade succeeds. In this case, she will sign the following message
Where \(m\) is formatted as follows
+---+---------+---------+-------------------+-------------------+-----------+-------+
value | 0 | 7 | 4 | 9000 | 15000 | nonce | ts |
+---+---------+---------+-------------------+-------------------+-----------+-------+
label A B C D E F G