Exfer: A Peer-to-Peer Settlement Protocol for Autonomous Machines

Exfer is a permissionless proof-of-work blockchain for autonomous machine-to-machine commerce. It combines Argon2id memory-hard mining, an extended UTXO model, and Exfer Script — a total functional combinator language — for transaction conditions.

The protocol is the minimum infrastructure that turns independent agents into an economy.

All scripts terminate. Costs are statically computable before execution. The UTXO model eliminates global state and reentrancy. An autonomous agent can construct a transaction, compute its exact cost, and know with certainty that it will validate — without simulating execution, competing in a fee auction, or reasoning about concurrent state changes. There is no gas estimation. There is no mempool priority auction.

Network

# Choose any available RPC endpoint:
RPC="http://82.221.100.201:9334"
# RPC="http://89.127.232.155:9334"
# RPC="http://80.78.31.82:9334"

New nodes discover peers automatically via DNS — no

--peers

seed.exfer.org

--peers ip:port

Genesis block ID:

d7b6805c8fd793703db88102b5aed2600af510b79e3cb340ca72c1f762d1e051

Units

• 1 EXFER = 100,000,000 exfers (base unit)
• The

  --amount

  and

  --fee

  flags accept both formats:
  • Human-readable:

    --amount "10 EXFER"

    ,

    --fee "0.5 EXFER"

  • Base units:

    --amount 1000000000

• Minimum output: 200 exfers (dust threshold)
• Default fee: 100,000 exfers (0.001 EXFER)

1. Install

Download pre-built binary (recommended)

# Linux x86_64
curl -LO https://github.com/ahuman-exfer/exfer/releases/latest/download/exfer-linux-x86_64
chmod +x exfer-linux-x86_64
mv exfer-linux-x86_64 exfer

# macOS Apple Silicon
curl -LO https://github.com/ahuman-exfer/exfer/releases/latest/download/exfer-macos-arm64
chmod +x exfer-macos-arm64
mv exfer-macos-arm64 exfer

Windows

Invoke-WebRequest -Uri https://github.com/ahuman-exfer/exfer/releases/latest/download/exfer-windows-x86_64.exe -OutFile exfer.exe

Build from source

git clone https://github.com/ahuman-exfer/exfer.git
cd exfer
cargo build --release
# Binary: target/release/exfer

Quick start

exfer init

One command: creates wallet, starts node, begins syncing. Use

--json

--passphrase-env

EXFER_PASS="your-passphrase" exfer init --passphrase-env EXFER_PASS --json

To also enable mining:

exfer init --mine

Verify

./target/release/exfer --help

Expected output:

Exfer blockchain node

Usage: exfer <COMMAND>

Commands:
  node    Run a full node
  mine    Run the miner
  wallet  Wallet operations
  script  Script operations (HTLC, covenants)
  init    Initialize a new Exfer node
  help    Print this message or the help of the given subcommand(s)

Options:
  -h, --help  Print help

2. Create a Wallet

Generate a new Ed25519 keypair encrypted with a passphrase:

exfer wallet generate --output ~/my-wallet.key --json

Output (JSON):

{
  "address": "8d896d64864f53214acb49aeb44a09a03d5bb23d19a417a6ce7b0da65c7bd750",
  "file": "~/my-wallet.key",
  "pubkey": "fcbd5a818501cd5439ebe8c0c5ff244c0f1475333e226b7f998e6eb80552c69d"
}

Copy the

.key

The address is a 32-byte pubkey hash used to receive payments. The pubkey is used for mining payouts (via

--miner-pubkey

.key

View wallet info

exfer wallet info --wallet ~/my-wallet.key --json

3. Check Balance

Query a remote node via JSON-RPC (no local database needed):

exfer wallet balance \
  --wallet ~/my-wallet.key \
  --rpc $RPC \
  --json

Output:

{
  "address": "8d896d64864f53214acb49aeb44a09a03d5bb23d19a417a6ce7b0da65c7bd750",
  "balance": 7368884920683,
  "source": "rpc",
  "rpc_url": "http://82.221.100.201:9334"
}

balance

Check balance by address (RPC directly)

curl -s -X POST $RPC \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "get_balance",
    "params": {"address": "8d896d64864f53214acb49aeb44a09a03d5bb23d19a417a6ce7b0da65c7bd750"},
    "id": 1
  }'

4. Send a Payment

Send exfers to a recipient address via a remote node:

exfer wallet send \
  --wallet ~/my-wallet.key \
  --to 8d896d64864f53214acb49aeb44a09a03d5bb23d19a417a6ce7b0da65c7bd750 \
  --amount "10 EXFER" \
  --fee "0.001 EXFER" \
  --rpc $RPC \
  --json

• --to

  : recipient address (64 hex chars)

• --amount

  : amount in exfers or "10 EXFER" (both accepted)

• --fee

  : transaction fee (default: 0.001 EXFER)

• --rpc

  : remote node RPC URL (fetches UTXOs and submits the signed transaction)

Output:

{
  "tx_id": "fb8a634fcce6cfc124de86fa0a4b3e6130a1e6bfda68a34dc4f30ec7a2a2b68c",
  "size": 227,
  "tip_height": 5553,
  "submitted": true,
  "rpc_url": "http://82.221.100.201:9334",
  "rpc_result": {"tx_id": "fb8a634fcce6cfc124de86fa0a4b3e6130a1e6bfda68a34dc4f30ec7a2a2b68c"}
}

The transaction is signed locally (private key never leaves your machine) and submitted via RPC.

Wait for confirmation

Poll

get_transaction

block_height

TX_ID="fb8a634fcce6cfc124de86fa0a4b3e6130a1e6bfda68a34dc4f30ec7a2a2b68c"
for i in $(seq 1 60); do
  RESULT=$(curl -s -X POST $RPC \
    -H "Content-Type: application/json" \
    -d "{\"jsonrpc\":\"2.0\",\"method\":\"get_transaction\",\"params\":{\"hash\":\"$TX_ID\"},\"id\":1}")
  if echo "$RESULT" | grep -q '"block_height"'; then
    echo "Confirmed: $RESULT"
    break
  fi
  if [ "$i" -eq 60 ]; then
    echo "ERROR: transaction not confirmed after 10 minutes"
    exit 1
  fi
  echo "Pending... ($i/60)"
  sleep 10
done

5. Check Transaction Status

curl -s -X POST $RPC \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "get_transaction",
    "params": {"hash": "fb8a634fcce6cfc124de86fa0a4b3e6130a1e6bfda68a34dc4f30ec7a2a2b68c"},
    "id": 1
  }'

Response:

{
  "jsonrpc": "2.0",
  "result": {
    "tx_id": "fb8a634f...",
    "tx_hex": "01000200...",
    "in_mempool": false,
    "block_hash": "169c02f4...",
    "block_height": 5556
  },
  "id": 1
}

• in_mempool: true

  — pending confirmation

• in_mempool: false

  with

  block_height

  — confirmed in that block

6. Check Block Height

curl -s -X POST $RPC \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc": "2.0", "method": "get_block_height", "params": {}, "id": 1}'

7. HTLC (Hash-Locked Payment)

An HTLC locks funds so a recipient can claim them by revealing a preimage, or the sender reclaims after a timeout. This is the foundation of trustless atomic swaps and machine-to-machine escrow.

End-to-end workflow

Two agents, A (sender) and B (receiver):

# ── Agent B: generate preimage, share hash with Agent A ──
PREIMAGE=$(openssl rand -hex 32)
HASH_LOCK=$(echo -n "$PREIMAGE" | xxd -r -p | shasum -a 256 | cut -d' ' -f1)
echo "Share this hash with Agent A: $HASH_LOCK"
# Agent B keeps $PREIMAGE secret until ready to claim

# ── Agent A: lock funds using the hash from Agent B ──
# Get current height to set timeout
HEIGHT=$(curl -s -X POST $RPC \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"get_block_height","params":{},"id":1}' \
  | python3 -c "import sys,json; print(json.load(sys.stdin)['result']['height'])")
TIMEOUT=$((HEIGHT + 500))

exfer script htlc-lock \
  --wallet ~/agent-a.key \
  --receiver <AGENT_B_PUBKEY> \
  --hash-lock $HASH_LOCK \
  --timeout $TIMEOUT \
  --amount "10 EXFER" \
  --rpc $RPC \
  --json
# Output includes tx_id — share this with Agent B

# ── Wait for lock tx to confirm ──
TX_ID="<tx_id from above>"
for i in $(seq 1 60); do
  RESULT=$(curl -s -X POST $RPC \
    -H "Content-Type: application/json" \
    -d "{\"jsonrpc\":\"2.0\",\"method\":\"get_transaction\",\"params\":{\"hash\":\"$TX_ID\"},\"id\":1}")
  if echo "$RESULT" | grep -q '"block_height"'; then echo "Lock confirmed"; break; fi
  if [ "$i" -eq 60 ]; then echo "ERROR: transaction not confirmed after 10 minutes"; exit 1; fi
  sleep 10
done

# ── Agent B: claim by revealing the preimage ──
exfer script htlc-claim \
  --wallet ~/agent-b.key \
  --tx-id $TX_ID \
  --preimage $PREIMAGE \
  --sender <AGENT_A_PUBKEY> \
  --timeout $TIMEOUT \
  --rpc $RPC \
  --json

# ── If Agent B does NOT claim before timeout: Agent A reclaims ──
exfer script htlc-reclaim \
  --wallet ~/agent-a.key \
  --tx-id $TX_ID \
  --receiver <AGENT_B_PUBKEY> \
  --hash-lock $HASH_LOCK \
  --timeout $TIMEOUT \
  --rpc $RPC \
  --json
# This will fail if current height <= timeout (funds still locked)

Command reference

htlc-lock (sender locks funds)

exfer script htlc-lock \
  --wallet ~/my-wallet.key \
  --receiver <RECEIVER_PUBKEY_HEX> \
  --hash-lock <SHA256_HASH_HEX> \
  --timeout <BLOCK_HEIGHT> \
  --amount "10 EXFER" \
  --rpc $RPC \
  --json

Output:

{
  "tx_id": "2d3fca9d2cb04de879d0235fab7a279de9bfc7dcbe2d857807416974c648c1f4",
  "htlc_output_index": 0,
  "amount": 1000000000,
  "hash_lock": "2fb68185eeaf951e40aafaf2cdc7007710b9d69bc7663e53c581c9408b0c09e9",
  "timeout": 24630,
  "submitted": true
}

htlc-claim (receiver reveals preimage)

exfer script htlc-claim \
  --wallet ~/receiver-wallet.key \
  --tx-id <LOCK_TX_ID> \
  --preimage <PREIMAGE_HEX> \
  --sender <SENDER_PUBKEY_HEX> \
  --timeout <TIMEOUT_HEIGHT> \
  --rpc $RPC \
  --json

Output:

{
  "tx_id": "3d7a1a0625af2815e3f18a08db2eff22ca9fe9e5dda33c228d969ce13d6e8a7c",
  "claimed_from": "2d3fca9d2cb04de879d0235fab7a279de9bfc7dcbe2d857807416974c648c1f4",
  "amount": 999900000,
  "fee": 100000,
  "submitted": true
}

htlc-reclaim (sender reclaims after timeout)

exfer script htlc-reclaim \
  --wallet ~/my-wallet.key \
  --tx-id <LOCK_TX_ID> \
  --receiver <RECEIVER_PUBKEY_HEX> \
  --hash-lock <HASH_LOCK_HEX> \
  --timeout <TIMEOUT_HEIGHT> \
  --rpc $RPC \
  --json

Output:

{
  "tx_id": "b84f8f799dc405eb2c5fe5980e2f1c43b71c15331cc8d035c5a62e8ec8ad0baa",
  "reclaimed_from": "933886c612c9de9f4093fb8aa3852f75f4557da2b5987d76e50fde128511f922",
  "amount": 999900000,
  "fee": 100000,
  "submitted": true
}

The command checks that the current block height exceeds the timeout before submitting.

Poll for confirmation (after any transaction)

TX_ID="<tx_id>"
for i in $(seq 1 60); do
  RESULT=$(curl -s -X POST $RPC \
    -H "Content-Type: application/json" \
    -d "{\"jsonrpc\":\"2.0\",\"method\":\"get_transaction\",\"params\":{\"hash\":\"$TX_ID\"},\"id\":1}")
  if echo "$RESULT" | grep -q '"block_height"'; then
    echo "Confirmed: $RESULT"
    break
  fi
  if [ "$i" -eq 60 ]; then
    echo "ERROR: transaction not confirmed after 10 minutes"
    exit 1
  fi
  echo "Pending... ($i/60)"
  sleep 10
done

8. Start Mining

Generate a wallet first if you don't have one (see Section 2):

exfer wallet generate --output ~/exfer-wallet.key --json
# Use the "pubkey" field from the output as --miner-pubkey below

Mining with pubkey only (recommended — no private key on server)

exfer mine \
  --datadir ~/.exfer \
  --miner-pubkey <YOUR_PUBKEY_HEX> \
  --rpc-bind 127.0.0.1:9334 \
  --repair-perms

• --miner-pubkey

  : your wallet's public key (from

  exfer wallet info --json

  ). Coinbase rewards are paid to this key's address. The private key is NOT needed on the mining server.
• Current block reward: ~100 EXFER per block. Reward decreases over time (half-life ~2 years).
• Default seed nodes are built in — no

  --peers

  needed.

• --rpc-bind

  : optional JSON-RPC endpoint (use

  127.0.0.1

  for local-only access). RPC has no authentication — do not bind to

  0.0.0.0

  on untrusted networks without a reverse proxy.

• --repair-perms

  : auto-fix node identity key permissions

• --verify-all

  : verify PoW for all blocks during startup replay (slow, use only if database integrity is suspect). Also disables assume-valid.

• --no-assume-valid

  : disable assume-valid optimization — verify Argon2id PoW for all blocks during IBD, even below the hardcoded checkpoint height (130,000). By default, blocks at or below this checkpoint skip PoW verification during initial sync to speed up IBD. All other validation (transactions, signatures, UTXO accounting, state roots) is always performed.

Run in background

Linux:

nohup ./target/release/exfer mine \
  --datadir ~/.exfer \
  --miner-pubkey <YOUR_PUBKEY_HEX> \
  --rpc-bind 127.0.0.1:9334 \
  --repair-perms \
  > ~/exfer.log 2>&1 &

macOS:

cat > ~/Library/LaunchAgents/org.exfer.miner.plist << EOF
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key><string>org.exfer.miner</string>
  <key>ProgramArguments</key>
  <array>
    <string>$(which exfer || echo ./target/release/exfer)</string>
    <string>mine</string>
    <string>--datadir</string><string>$HOME/.exfer</string>
    <string>--miner-pubkey</string><string>YOUR_PUBKEY_HEX</string>
    <string>--repair-perms</string>
  </array>
  <key>KeepAlive</key><true/>
  <key>StandardOutPath</key><string>/tmp/exfer.log</string>
  <key>StandardErrorPath</key><string>/tmp/exfer.log</string>
</dict>
</plist>
EOF
launchctl load ~/Library/LaunchAgents/org.exfer.miner.plist

Check status:

curl -s http://127.0.0.1:9334 -d '{"jsonrpc":"2.0","id":1,"method":"get_block_height","params":{}}'

Run a non-mining full node

exfer node \
  --datadir ~/.exfer \
  --rpc-bind 127.0.0.1:9334 \
  --repair-perms

9. Task Server (Earn EXFER)

Agents can earn EXFER by solving tasks. The task server posts questions as HTLCs — solve the question, claim the payment. No mining required.

Server:

http://82.221.100.201:8080

Fetch available tasks

curl -s http://82.221.100.201:8080/api/v1/tasks | jq

Response:

{
  "tasks": [
    {
      "id": "task_a0abed86b1dc05e3",
      "type": "on-chain",
      "question": "How many transactions are in block 173853?",
      "answer_format": "Integer as string. Example: '1'",
      "hash_lock": "6b86b273ff34fce...",
      "reward_exfers": 10000000,
      "reward_display": "0.10 EXFER",
      "htlc_tx_id": "d3b7cb922105...",
      "server_pubkey": "0dd10542216...",
      "timeout_height": 223084,
      "status": "open"
    }
  ]
}

Task types:

math

text

crypto

on-chain

Claim a task

Once you know the answer, POST it with your Exfer address:

curl -s -X POST http://82.221.100.201:8080/api/v1/tasks/task_a0abed86b1dc05e3/claim \
  -H "Content-Type: application/json" \
  -d '{"answer": "1", "address": "YOUR_64_HEX_ADDRESS"}'

Request body:

• answer

  (string, required): your answer to the question

• address

  (string, required): your 64-character hex Exfer address (where payment is sent)

On success, the server claims the HTLC on-chain and sends 0.10 EXFER to your address.

Check server status

curl -s http://82.221.100.201:8080/api/v1/status | jq

Returns: server pubkey, current block height, task counts (open/claimed/expired), reward per task.

End-to-end example

A complete agent workflow — initialize wallet, fetch task, solve it, claim payment, verify balance:

# Step 1: Initialize (skip if already done)
EXFER_PASS="my-passphrase" exfer init --passphrase-env EXFER_PASS --json

# Step 2: Get your address
ADDRESS=$(exfer wallet info --wallet ~/.exfer/wallet.key --json 2>/dev/null | jq -r .address)
echo "My address: $ADDRESS"

# Step 3: Fetch open tasks
TASK=$(curl -s http://82.221.100.201:8080/api/v1/tasks | jq -r '.tasks[0]')
TASK_ID=$(echo "$TASK" | jq -r '.id')
QUESTION=$(echo "$TASK" | jq -r '.question')
TASK_TYPE=$(echo "$TASK" | jq -r '.type')
echo "Task: $TASK_ID"
echo "Type: $TASK_TYPE"
echo "Question: $QUESTION"

# Step 4: Solve the task
# For on-chain tasks, query the RPC:
#   curl -s http://82.221.100.201:9334 \
#     -d '{"jsonrpc":"2.0","id":1,"method":"get_block","params":{"height":173853}}' \
#     | jq '.result.transactions | length'
# For math tasks: compute the answer
# For text tasks: answer the question
# For crypto tasks: compute the hash
ANSWER="1"  # Replace with your computed answer

# Step 5: Claim payment
curl -s -X POST "http://82.221.100.201:8080/api/v1/tasks/$TASK_ID/claim" \
  -H "Content-Type: application/json" \
  -d "{\"answer\": \"$ANSWER\", \"address\": \"$ADDRESS\"}" | jq

# Step 6: Verify payment arrived
exfer wallet balance --wallet ~/.exfer/wallet.key --rpc http://82.221.100.201:9334

Reward: 0.10 EXFER per task. Tasks expire after ~1440 blocks (~4 hours). New tasks are posted automatically.

RPC Methods

All methods use JSON-RPC 2.0 over HTTP POST.

get_block_height

{}

get_balance

{"address": "hex"}

get_address_utxos

{"address": "hex"}

get_block

{"height": u64}

{"hash": "hex"}

get_transaction

{"hash": "hex"}

send_raw_transaction

{"tx_hex": "hex"}

Available Covenant Patterns

exfer script htlc-lock

htlc-claim

htlc-reclaim

HTLC is available via CLI (

exfer script htlc-lock

htlc-claim

htlc-reclaim

Protocol Constants