• "Code trumps docs" — Juliano Rizzo (Coinspect)
• Huge chasm to cross → effort/ times
• RFCs/IPs → nice in-between
• Examine the history easily → decision log

• Hashgraph → Consensus algorithm
• Hedera → The "blockchain" network

Early days

• Layer-2 Smart Contract Network
• Migrate Smart Contract Service EVM to Hyperledger Besu EVM

EVM Compatibility - Fundamentals

• Smart Contract Service Gas Based Throttling 🛠️
• Expand alias support in CryptoCreate & CryptoTransfer Transactions 🛠️
• Account Virtual Addresses

EVM Compatibility - Architecture

• Wrapping Ethereum Transaction Bytes in a Hedera Transaction 🛠️
• JSON-RPC Relay 🛠️
• Introduction Of Blocks

Pre-compiles for services

• Exchange rate system contract 🛠️
• Add UtilPrngTransaction 🛠️

Attempting to integrate EVM capabilities

• HIP-11: Layer-2 Smart Contract Network
• HIP-26: Migrate Smart Contract Service EVM to Hyperledger Besu EVM

• L2 network on the existing L1 network
• L1: Original Hedera
• L2: EVM-compatible
• This was not the path taken

• Current EVM impl started here

Finding parallels between way it works currently, and the EVM way of working

• HIP-583: Expand alias support in CryptoCreate & CryptoTransfer Transactions
• HIP-631: Account Virtual Addresses
• HIP-185: Smart Contract Service Gas Based Throttling

• Hedera Account ID ↔ Ethereum Address String
• Hedera Account Num Alias ↔ Ethereum Address String
• Hedera Key Alias ↔ Ethereum Address String
• EVM Address Alias ↔ Ethereum Address String

Conversions:

0.0.12345 --> 0x0000000000000000000000000000000000003039

17.2049.12345 --> 0x0000001100000000000008010000000000003039

• Relationship between Hedera-native accounts and EVM accounts
• This also references the long-zero address term

• Transaction count limit + gas limit
• Penalty: Set max gas to more than 125% of actual gas used
• Impl: Refund of unused gas is limited to 20% of the max gas sent
• Prevents over-reservation for transactions
• Gas estimation: Impl coming soon (HIP-584)

On Ethereum:

• gasUsed = gasConsumed
• Full refund, always

On Hedera:

• gasUsed = max(gasConsumed, gasLimit * 0.8)
• Partial refund, when gasLimit too high

Re-architecting to keep original network functional, while refactoring it to include EVM components

• HIP-410: Wrapping Ethereum Transaction Bytes in a Hedera Transaction
• HIP-482: JSON-RPC Relay
• HIP-415: Introduction Of Blocks

• gRPC HAPI as the comms protocol - not JSON-RPC
• so: adda a new gRPC HAPI transaction type - wrap JSON-RPC
• Foundation for all EVM-compatible software to interact with Hedera's EVM

• Smallest unit: Tinybar = 10HBAR.
• New "virtual" unit introduced: Weibars = 10HBAR
• Weibars are auto rounded-down (floor)

• Deploy contract and invoke checkBalance
• Observe if "full unit" is 10^18 vs 10^8

• hedera-services consensus nodes
• hedera-mirror-node archival nodes
• hedera-json-rpc-relay JSON-RPC interface - HAPI (gRPC) - Custom Mirror API (HTTP, REST-style) - JSON-RPC (HTTP and WS)
• RPC is compatible with geth (a subset)

• Run an RPC Relay server
• Request net_version, eth_blockNumber, and eth_getBalance
• Note balance on RPC is 10^18 instead of 10^8

• In Hedera consensus on transactions, not blocks
• Hashgraph consensus: Directed acyclic graph - Nodes: Transactions - Vertices: Gossip about known previous transactions
• Blockchain consensus: Singly linked list - Nodes: Blocks (of transactions) - Links: Block hash of previous block
• Natively, no blocks --> Virtual blocks
• Mirror nodes ingest transactions in groups --> Record files

• Convert current timestamp to block number
• Query that block over JSON-RPC
• Note that transactions list is empty: Only EVM transactions are shown

System contracts are introduced to provide an interface to existing Hedera services

• HIP-475: Exchange rate system contract
• HIP-351: Add UtilPrngTransaction

• Hedera services are priced in USD terms; not gas units
• When a smart contract invoked services, fees need to be paid in gas
• Impact on: Price volatility? Unidirectional exchanges? Econs!!!
• Important: Not a "live" rate

• Deploy smart contract that interacts with system contract
• Invoke the convert function

• PRNG
• 3rd party can verify in RNG truly occurred on Hedera
• BYO CSPRNG (can use this as an input)
• Fixed USD cost ($0.001) --> Exchange rate system contract --> Gas units

• Deploy smart contract that interacts with system contract
• Invoke the getPseudorandomNumber function

• Hard-mode when: - Not technically a blockchain - Existing account system w/ different public key system - Different set of comms protocols, - Gas fees that require an exchange rate
• Add EVM compatibility → Can be a multi-year effort

docs.hedera.com

Tips:

• Most existing EVM-compatible dev workflows work out of the box
• Run your own RPC relay on localhost
• To get Testnet coins, use portal.hedera.com
• Use the hedera tag on Stackoverflow