> For the complete documentation index, see [llms.txt](https://docs.bit-bank.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.bit-bank.io/the-bit-bank-ecosystem/xshield/anonymous-assets.md).
# Anonymous Assets
Bit Bank network allows for the issuance and transfer of anonymous assets with an arbitrary number of parameters. These tokens are anonymous, relying on zero-knowledge proofs to ensure validity without revealing any other information.
New tokens are created and destroyed every time you send an anonymous transaction. To send a transaction on Bit Bank, you must first issue a credential that commits to some value you have in your wallet. This is called the **Mint** phase. Once the credential is spent, it destroys itself: what is called the **Burn.**
Through this process, the link between inputs and outputs is broken.
### Mint
During the **Mint** phase we create a new coin C , which is bound to the public key P. The coin C is publicly revealed on the blockchain and added to the merkle tree, which is stored locally on the Bit Bank wallet.
We do this using the following process:
Let v be the coin's value. Generate random rC, rV and serial ρ.
Create a commitment to these parameters in zero-knowledge:
$$
C=H(P,v,ρ,rC)
$$
Check that the value commitment is constructed correctly:
$$
v>0V=vG1+rVG2
$$
Reveal C and V. Add C to the Merkle tree.
### Burn
When we spend the coin, we must ensure that the value of the coin cannot be double spent. We call this the *Burn* phase. The process relies on a N nullifier, which we create using the secret key x for the public key P. Nullifiers are unique per coin and prevent double spending. R is the Merkle root. v is the coin's value.
Generate a random number rV.
$$
N=H(x,ρ)
$$
Check that the secret key corresponds to a public key:
$$
P=xG
$$
Check that the public key corresponds to a coin which is in the merkle tree R:
$$
C=H(P,v,ρ,rC)C∈R
$$
Check that the value commitment is constructed correctly:
$$
v>0V=vG1+rVG2
$$
Reveal N, V and R. Check R is a valid Merkle root. Check N does not exist in the nullifier set.
The zero-knowledge proof confirms that N binds to an unrevealed value C, and that this coin is in the Merkle tree, without linking N to C. Once the nullifier is produced the coin becomes unspendable.
### Adding values
Assets on Bit Bank can have any number of values or attributes. This is achieved by creating a credential C and hashing any number of values and checking that they are valid in zero-knowledge.
We check that the sum of the inputs equals the sum of the outputs. This means that:
$$
B=∑Vin−∑Vout
$$
And that B is a valid point on the curve G2.
This proves that B=0G1+bG2=bG2 where b is a secret blinding factor for the amounts.
## Diagram
