proxmox/docs/archive/QBFT_VALIDATOR_KEY_INVESTIGATION.md

QBFT Validator Key Configuration Investigation

Date: $(date)
Issue: Validators are connected but not producing blocks - they're looking for sync targets instead

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Problem Summary

• ✅ 5 validators connected to network
• ✅ All configuration files correct
• ✅ Validator keys present at /keys/validators/validator-{N}/
• ❌ Validators are searching for "sync targets" instead of producing blocks
• ❌ Still at block 0 (genesis)

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Critical Finding

Log Message Pattern:

Unable to find sync target. Currently checking 8 peers for usefulness

This suggests that Besu thinks these nodes need to sync from other nodes, rather than recognizing them as validators that should produce blocks.

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Current Configuration

Validator Config (config-validator.toml)

miner-enabled=false
miner-coinbase="0x0000000000000000000000000000000000000000"
sync-mode="FULL"

Validator Keys Location

• /keys/validators/validator-{N}/key.priv ✅ Present
• /keys/validators/validator-{N}/address.txt ✅ Present
• /keys/validators/validator-{N}/key.pem ✅ Present

Genesis Configuration

• QBFT config: {blockperiodseconds: 2, epochlength: 30000, requesttimeoutseconds: 10}
• No validators array (correct for dynamic validators)
• extraData contains 5 validator addresses (RLP-encoded)

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Research Findings

1. Validator Key Discovery

• Besu may need explicit configuration to find validator keys
• Keys are at /keys/validators/validator-{N}/ but Besu might not auto-discover them
• Documentation mentions "Each validator node references its key directory in config-validator.toml" but we don't see this in current config

2. QBFT Dynamic Validators

• Network uses dynamic validator management (no static validators array in genesis)
• Initial validator set comes from extraData field
• Validators still need to know their own key to sign blocks

3. Miner Configuration

• miner-enabled=false is correct for QBFT (QBFT doesn't use mining)
• But miner-coinbase might need to be set to validator address for QBFT to recognize the node as a validator

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Possible Solutions to Investigate

Option 1: Set miner-coinbase to Validator Address

miner-coinbase="0x<validator-address>"

• Each validator would use its own address from /keys/validators/validator-{N}/address.txt
• This might tell Besu "I am a validator, produce blocks"

Option 2: Configure Validator Key Path

• Research if Besu has a validator-keys-path or similar config option
• Or if keys need to be in a specific location that Besu checks by default

Option 3: Verify Key Loading

• Check logs for messages about loading validator keys
• If no key loading messages, Besu may not be finding/using the keys

Option 4: Check Initial Validator Set

• For dynamic validators, verify that the initial set from extraData is correct
• Ensure all 5 validators are in the initial set

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Next Steps

1. ✅ Verify validator addresses match genesis extraData (DONE - all match)
2. ⏳ Check logs for validator key loading messages
3. ⏳ Research if miner-coinbase should be set to validator address
4. ⏳ Test setting miner-coinbase to each validator's address
5. ⏳ Check if Besu needs explicit validator key path configuration

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Key Insight

The fact that validators are looking for "sync targets" instead of producing blocks suggests that Besu doesn't recognize these nodes as validators.

In QBFT, validators should:

• NOT be looking for sync targets
• Be actively participating in consensus
• Proposing blocks based on their turn in the validator rotation

This is likely a validator key configuration issue rather than a network connectivity issue.

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Last Updated: $(date)
Status: Investigating validator key configuration for QBFT block production