Instruction to Anonymous Tansaction in Mixin Network

Privacy protection is one of the purposes of designing the Mixin Network. This article briefly talks about how the Mixin Network uses the CryptoNote protocol to enhance privacy.

Mixin Network’s transactions are based on UTXO like Bitcoin, not the accounting model. Mixin Network, like Bitcoin, uses a public address consisting of pseudo-random numbers and letters derived from the user’s public key, with the address as the user’s public ID.

Unlike Bitcoin, however, the Mixin Network is based on the CryptoNote protocol, which hides the association between sender and receiver addresses. That is to say, if the address A actually sends a transaction to the address B, with Bitcoin you can find a transaction from A to B through the transaction record, but you cannot see the transaction between address A and address B on the Mixin Network.

So how does Mixin Network do it? Let’s briefly explain the implementation of the Mixin Network based on the CryptoNote protocol.

In Bitcoin transactions, once an address is published, it becomes an explicit identifier for revenue payments. Moreover, the links between different addresses are made through the transaction, and it is easy to track the links between multiple addresses.

Mixin Network’s CryptoNote-based solution allows users to post transactions that are not linked. The destination of each output (by default) is a one-time public key derived from the recipient’s address and the random number constructed by the sender. By default, this one-time public key is unique (unless the sender uses the same random number to send to the same address). Therefore there is no problem with “address reuse”.

In our scenario, the public and private keys are divided into two parts, the public key is represented as (A, B) and the private key is represented as (a, b). We also use the EdDSA signature algorithm based on the elliptic curve. The relevant parameters mentioned below include a base point G = (x, -4/5); I is a constant; Hs is a cryptographic hash function; and according to the characteristics of the elliptic curve A = aG, B = bG, we make it mandatory that a is not equal to b.

For example, Alice wants to send a transaction to Bob who has already given her his address. She gets Bob’s public key (A, B) from the address, then generates a random number r∈[1，I -1], and computes the one-time address P = Hs（rA）G + B.

Alice uses P as the destination address for the output and packages the value R = rG (as part of the Diffie-Hellman exchange) into the transaction.

So how do you verify the progress of trading? Bob checks each transaction received using his private key (a, b) and calculates P’ = Hs（aR）G + bG. If the transaction Alice sent with Bob as the recipient is in them, then aR = arG = rA (because it was mentioned above that aG = A), then P’ = P. we can confirm that the transaction is sent to Bob.

In addition, Bob can restore the corresponding one-time private key: x = Hs（aR）+ b, and we will also find P = xG. Bob can spend the transaction at any time by signing the transaction with this one-time private key x.

So can this way protect privacy? Let’s review it again.

Privacy protection of both parties

In order to prevent sender identification, we only construct a transaction with a random number constructed by the sender, making it impossible to determine who actually sent the transaction, protecting the sender’s privacy.

At the receiving end, we generate a one-time public key and one-time address for each transaction, even for the same sender and receiver. The privacy of the recipient is also well protected.

In addition, the sender generates a one-time temporary key for each transmission and only the recipient can recover the corresponding private key to ensure the security of the asset. No third party can determine whether two different transactions have been sent to the same recipient.

Mixin Network anonymous transaction

In conclusion, the implementation of Mixin Network based on CryptoNote protocol guarantees both privacy and asset security. The above is how Mixin Network protects privacy. We will have a series of technical articles related to the implementation of Mixin technology.