Suyash Bagad
Cryptography Engineer
Aztec's DeFi Bridge
A walkthrough of the upcoming updates to Aztec 2.0
A Simple DeFi Example
ZK Money
DeFi Bridge
\(v^{\text{in}}_1 = 1\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(v^{\text{in}}_2 = 0.5\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(v^{\text{out}}_1 = 4500\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(v^{\text{out}}_2 = 0.15\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
DeFi Bridge
\(v^{\text{in}}_1 = 1\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(v^{\text{in}}_2 = 0.5\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(v^{\text{out}}_1 = 4500\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(v^{\text{out}}_2 = 0.15\)
\(A = \texttt{0xF5C...17}\)
\(n = 15, s = \texttt{0x8C...2}\)
\(d = 1.5\)
\(n_d = 4\)
\(P = H(A, n, s)\)
\(\texttt{DeFi Deposit}\)
\(\texttt{DeFi Claim}\)
\(\texttt{Claim Note}\)
DeFi Bridge
\(v_1 = 0.4\)
\(v_2 = 0.8\)
\(d_1 = 1.2\)
\(v_3 = 1\)
\(v_4 = 0.1\)
\(d_2 = 1.1\)
\(v_5 = 0.05\)
\(v_6 = 0.15\)
\(d_3 = 0.2\)
\(v_7 = 0.3\)
\(v_8 = 0.1\)
\(d_4 = 0.4\)
\(v_9 = 0.2\)
\(v_{10} = 0.6\)
\(d_5 = 0.8\)
\(d_{\text{in}} = 3.7\)
\(n_d = 4\)
\(\texttt{in}\)
\(\texttt{out}\)
\(v_{\text{out}, 1} = 11,100\)
\(v_{\text{out}, 2} = 0.37\)
\(+\)
\(\texttt{DeFi Interaction Note}\)
\(v_1 = 3600\)
\(v_2 = 0.12\)
\(v_3 = 3300\)
\(v_4 = 0.11\)
\(v_5 = 600\)
\(v_6 = 0.02\)
\(v_7 = 1200\)
\(v_8 = 0.04\)
\(v_9 = 2400\)
\(v_{10} = 0.08\)
Collateralised Loans
\(v_1 = 0.4\)
\(v_2 = 0.6\)
\(d = 1\)
\(b_{\text{id}}=b_1\)
\(\texttt{Block }k\)
\(d = 1\)
\(b_{\text{id}}=b_1\)
\(\texttt{in}\)
\(\texttt{out}\)
\(\longleftrightarrow\)
\(v_1 = 3000\)
\(v_2 = 3000\)
\(\text{id} = (01 \ \| \ \underbrace{n_d}_{\substack{30}})\)
\(d_{\text{in}} = 5\)
\(n_d = 4\)
\(v_{\text{DAI}} = 15\text{K}, v_{\text{debtETH}} = 5\)
\(\texttt{is\_loan} = 1\)
\(\texttt{Block }\ge (k+1)\)
\(\texttt{Getting Loan against collateral}\)
Collateralised Loans
\(\texttt{Block }(k+1000)\)
\(\texttt{in}\)
\(\texttt{out}\)
\(\longleftrightarrow\)
\(v_1 = 3000\)
\(v_2 = 3000\)
\(\text{id} = (01 \ \| \ n_d)\)
\(v_{\text{ETH}} = 2.7, \ v_{\text{Aave}} = 0.6\)
\(\texttt{is\_loan} = 0\)
\(\texttt{Block }\ge (k+1001)\)
\(\texttt{Loan repayment}\)
\(v_1 = 0.9\)
\(v_2 = 0.2\)
\(d = 3000\)
\(b_{\text{id}}=(n_d \ \| \ b_2)\)
\(d = 3000\)
\(b_{\text{id}}=(n_d \ \| \ b_2)\)
\(n_d\)
\(\% \text{ pa}\)
\(4\)
\(10\)
\(7\)
\(6.7\)
\(\vdots\)
\(\vdots\)
\(d_{\text{in}} = 9000\)
\(n'_d = 19\)
Collateralised Loans
\(\texttt{Loan repayment in Installments}\)
\(v_4 = 2000\)
\(\text{id} = (01 \ \| \ n_d)\)
\(v_3 = 1000\)
\(\text{id} = (01 \ \| \ n_d)\)
\(v_2 = 1000\)
\(v_1 = 0.3\)
\(v_2 = 0.067\)
\(v_5 = 2000\)
\(v_{\text{ETH}} = 1, \ v_{\text{Aave}} = 0.8\)
\(d = 3000\)
\(b_{\text{id}}=(n_d \ \| \ b_2)\)
\(d_{\text{in}} = 4000\)
\(n'_d = 25\)
\(v_1 = 0.5\)
\(v_2 = 0.4\)
\(v_{\text{ETH}} = 2.7, \ v_{\text{Aave}} = 0.6\)
\(d_{\text{in}} = 9000\)
\(n'_d = 19\)
\(d = 1000\)
\(b_{\text{id}}=(n_d \ \| \ b_2)\)
\(v_1 = 3000\)
\(\text{id} = (01 \ \| \ n_d)\)
Features
\(a_3 = 1\)
\(a_4 = 0.2\)
\(d_2 = 1.1\)
\(f_c = 0.05\)
\(a_1 = 0.4\)
\(a_2 = 0.8\)
\(a_1' = 1\)
\(a_2' = 0.2\)
\(d_3 = 0.2\)
\(d_3 = 3.7\)
\(a_{\text{out}, 1} = 11100\)
\(a_{\text{out}, 2} = 0.37\)
\(a_3' = 600\)
\(a_4' = 0.02\)
\(S_1\)
\(S_2\)
\(S_1'\)
\(S_2'\)
\(\texttt{Account Proof}\)
\(\texttt{Join-split Proof}\)
\(\texttt{Defi deposit Proof}\)
\(\texttt{Defi claim Proof}\)
- Rollup circuit must support 4 types of proofs, i.e. individual proof structures must be consistent
- Supports defi interactions for upto \(2^{30}\) assets
- A defi bridge is identified by its
\(\texttt{bridge\_id} = \bigg( \underbrace{\text{id}_{\text{out}, 2}}_{30} \ \| \ \underbrace{\text{id}_{\text{out}, 1}}_{30} \ \| \ \underbrace{\text{id}_{\text{in}}}_{30} \ \| \ \underbrace{n_{\text{in}}}_{2} \ \| \ \underbrace{\texttt{0xCF68...9E}}_{160} \bigg)\)
- Defi deposit sums to be accumulated
- Defi claim proofs to be generated individually
- Fee across defi deposit and claim is split
- Here, \(f_{\text{d}} = 0.05, f_{\text{c}} = 0.05\) (\(f_c\) added to claim note)
Challenges
- Although elegant, the defi bridge design brings some new challenges:
- Max two output assets allowed per defi protocol
- Max number of defi interactions per rollup is \(4\), remember every swap in Uniswap would be a unique defi interaction
- New bridge contracts for each defi protocol
- Increased circuit complexity (increased chances of bugs)
- User interface concerns due to asynchronous processing
- Censoring of claim proof processing
Summary
- In this part, we covered:
- Informal overview of Aztec's planned defi bridge
- How private and cheap transactions in defi would work
- Challenges of defi bridge
- In future, we might cover:
- How lookup tables work in practice
- How range constraints work
- How Shplonk commitment scheme works
- How fixed gate scalar multiplication in StdComposer work
- How new Plonk version works
Aztec's DeFi Bridge
By Suyash Bagad
Aztec's DeFi Bridge
A very short presentation explaining how defi-bridge in Aztec works.
