In Solidity, is it possible to craft a memory array of length 2**256 - 1?
Yes -> if function that creates the array is an internal call
No -> if function call is external. Reverts with out of gas error.
Code
github.com/t4sk/notes/blob/m…
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Math for vault and rebase token (like SUSDS and aToken) calculate the same redeemable amount with different mechanisms.
But in code, precision loss causes these 2 ways of calculations to diverge.
Notes
github.com/t4sk/notes?tab=re…
Code
github.com/t4sk/notes/blob/m…
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txgraph.org/
- Visualize transaction
- Compiles and visualizes Solidity contracts
- Code navigation if contract compiled
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I've received a fake job recruitment email from zendarox
Here are some things I do before clicking on any link.
1. Background check (google the company)
2. Hover over link to see if it matches text
3. Open links in browser's private mode
Stay safe
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I found out last night this is an invalid attack😳
Lido.transferToVault overrides AragonApp
Apology for the misinformation
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352
stETH has a function that
- transfers any token and ETH to a vault set by Lido
- any user can call
Vault address is 0
1. Find a way to
set the vault address
or deploy code at the 0 address
2. Report bug💰
Lido proxy
etherscan.io/address/0xae7ab…
Lido impl
etherscan.io/address/0x02827…
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Incremental Merkle Tree
Fast (O(H)) merkle root calculation for 2^H leaf nodes
Used by ETH deposit contract to prove ETH deposits to CL
Deposit contract
etherscan.io/address/0x00000…
Python
github.com/t4sk/notes/blob/m…
Solidity
github.com/t4sk/notes/blob/m…
Notes
github.com/t4sk/notes
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USDtb market cap $354M
1 owner (EOA)
owner can
1. grant mint role
2. mint any amount (for example 1 billion USD)
I pray the owner isn't a single private key
etherscan.io/address/0xc1391…
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Contract that uses 1251 slots deployed for only $26
It stores a lookup table from b to x
x^(year in seconds) = 1 + b/1e4
etherscan.io/address/0xea91a…
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10,996
Epsiode 17 - lonelysloth piped.video/EdCZJiaVRjs?si=ZOGh… via @YouTube
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Math of WstETH
stETH is rebasing
WstETH is not
how does WstETH accounting work?
X = _getShareRateNumerator()) / _getShareRateDenominator()
Notes
github.com/t4sk/notes/blob/m…
WstETH
etherscan.io/address/0x7f39c…
stETH
etherscan.io/address/0xae7ab…
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2
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2,530
Schnorr signature scheme
- Uses Elliptic curve math (similar to ECDSA)
- A signature can easily be turned into multi-sig
- Multi-sig can be vulnerable to rogue key attack
- Used by Chronicle Labs price oracles
cantina.xyz/bounties/5240b7c…
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7
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4,469
Why reusing nonce when signing 2 different messages in ECDSA exposes the private key
Code
github.com/t4sk/notes/blob/m…
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Dollar cost average vault
Sell token = X
Buy token = Y
- User deposits X
- X earns yield from external DeFi
- X can be swapped to Y, rate limited by time and amount
- Oracle checks swap price
Code (not tested)
github.com/t4sk/notes/blob/m…
Math based on Liquity stability pool
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2,976
Elliptic curve addition
P + Q = R
For P != Q
1. Draw a line (L) through P and Q
2. Find where L intersects the elliptic curve (x2, y2)
3. Reflect on x-axis (x2, y2) -> (x2, -y2)
For P = Q
1. Draw tangent line of P
2 and 3 are the same
desmos.com/calculator/efumve…
1
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44
2,793
Cryptoshorts e02: Schnorr signature piped.video/r9hJiDrtukI?si=1kaY… via @YouTube
7
1,740
Privacy without Terrorists | Ameen Soleimani (0xbow) at ETHConf piped.video/3KZGIqJcsuU?si=vZKS… via @YouTube
5
1,457
Notes on mulDiv for Solidity devs
- Math theorems are treated as black boxes
- Why certain checks and operations are needed
- Why overflows are safe in some places
Code
github.com/t4sk/notes/blob/m…
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Simulation of a P-controller for interest rates of a lending protocol (pic 1)
Controller aims to keep utilization rate high (pic 3)
util < optimal -> decrease interest rate
util > optimal -> increase interest rate
Simulation (pic 2)
Yields (pic 4)
github.com/t4sk/notes/blob/m…
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Midnight morpho's math to calculate credit after slashing is the same math used in Liquity stability pool
Midnight code
github.com/morpho-org/midnig…
Liquity stability pool math
github.com/liquity/liquity/b…
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1. Swap 100 ETH to 100.001 stETH
2. Queue withdraw on LIDO (stETH to ETH)
3. Receive 100.001 ETH in 2 days
Net profit
$1676 / ETH * 0.001 ETH - gas = $1.676 - gas💀
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Review of 63 / 64 gas rule in EVM
An easy summary to remember, although slightly inaccurate, is that a naive gas refund mechanism can overpay the caller by about 1/64 of the gas sent
Code
github.com/t4sk/notes/blob/m…
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@cantinasecurity
Do you think it's fair to publish audit reports into out of scope after the contest has started?
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Vault inflation attack
x axis = donation amount
purple region = where attack is possible
green line = profit (attack vs no attack)
green line above y = 0 and inside purple region is where attack is profitable
Graph
desmos.com/calculator/orugjr…
Code + notes
github.com/t4sk/notes/tree/m…
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Optimal capital allocation is at the peak of the 1st graph
Graphs the sum of yield x user's position for reserve 0 and 1 (pic 1, 2, 3)
When change in yields are small, replacing the yield functions with constants approximates the exact solution (pic 4)
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Yield optimization for 2 reserves in Aave V3
Give initial capital of C, how much should you put in reserve 0 and 1 to maximize yield?
Assumptions
- Similar assets (DAI and USDC)
- Or slippage and fee on swap is 0
Graph
desmos.com/calculator/rrvybo…
Code
github.com/t4sk/notes/blob/m…
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[Andre Cronje | Flying Tulip] Advice to Builders & Why He Came Back piped.video/jbXFENvyziM?si=SbNx… via @YouTube
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AST grapher
click on contract to see list of state variables and functions
txgraph.vercel.app/?tab=ast
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2 columns to visualize Solidity contracts
left column - functions
right column - state variagles
1st picutre
Which functions read or write to this state variable?
2nd picture
Which functions and state variables does this function (balance()) touch?
txgraph.vercel.app/?tab=ast
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Soliditity AST visualizer
graphical representation of which state varaibles are touched when a function is called
txgraph.vercel.app/?tab=ast
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Ito's Lemma Clearly and Visually Explained piped.video/TgBzqdN24fo?si=wM0o… via @YouTube
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954
VDAO Ep 12 The Hidden Risks of Stablecoins (And Why Decentralization Mat... piped.video/TXGC6WKAOQY?si=scUs… via @YouTube
1
1
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2,010
Solidity AST visualizer
txgraph.vercel.app/?tab=ast
Current state - visualize inheritance (pic 1)
TODO
- Graph functions and state variables (pic 2)
- AST grapher for live contracts (pic 3)
Consider donating to any project on ETH security QF
My project
qf.giveth.io/project/transac…
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How a peg stability module can accidentally create unbacked stablecoin yield
Peg stability module - swaps stablecoins 1 to 1
Stablecoin savers earn yield by staking their stablecoin into the protocol
Primary yield typically comes from stablecoin borrowers
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The Inevitable COLLAPSE of The Financial System | Lyn Alden piped.video/NUaNrRBvKHQ?si=4Fb-… via @YouTube
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1,055
Incremental Merkle tree animations
1. Initialization (caching zero hashes)
2. Inserts (caching right most left nodes)
Code
github.com/t4sk/notes/blob/m…
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Web3 companies are posting jobs on jobs.ashbyhq.com
Here is how to find them
1. Google "site:jobs.ashbyhq.com defi"
2. Filter by date (last month)
Replace "defi" with other keywords
Positions I found
gist.github.com/t4sk/faed549…
Good luck
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Borrow GHO -> pay 3.05%
Deposit GHO -> receive 4.73%
Free money, except you cant borrow GHO at the moment
app.aave.com/sgho/
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3,792
Clever way to reverse 32 bytes
simple method -> 32 iterations
clever method -> 5 iterations
# input
A B C D E F G H
# swap 1 byte
B A D C F E H G
# swap 2 bytes
D C B A H G F E
# swap 4 bytes
H G F E D C B A
Code
github.com/risc0/risc0-ether…
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Protocol insurance
1. Insuree pays premium to stakers
2. In a bad event, contracts are halted and stakers pay the insuree
3. Staker withdrawal are queued to prevent bank runs
Code
github.com/t4sk/defi-cookboo…
Deployment tx
tx-graph-eight.vercel.app/tx…
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KZG Polynomial Commitment Scheme | Zero Knowledge Proofs for Developers ... piped.video/SHtW-1IYfC8?si=i1oF… via @YouTube
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1,261
ZKSTARK
Why FRI detects a dishonest prover
- Proximity gap theorem (optional)
- Distance preservation under fold
- Honest and dishonest prover
Notes
github.com/t4sk/notes/tree/m…
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Free Money: An Economic System piped.video/74s7_KGg2fo?si=W5DA… via @YouTube
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1,594
ZKSTARK
- FRI (Intro, notations, commit and query)
More notes
github.com/t4sk/notes/tree/m…
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1,483
Namespace for storage variables without clever code like this
github.com/OpenZeppelin/open…
After a little experiment, I concluded that it was indeed confusing since Solidity creates read only functions for public state variables, these functions will have $ prefix.
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How is it possible that a call to address(1) returns data?
Precompiles
address(1) = call to ecrecover
transaction
tx-graph-eight.vercel.app/tx…
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