36 lines
1.6 KiB
Markdown
36 lines
1.6 KiB
Markdown
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# ADR-004: Tor Hidden Services for Peer Communication
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**Status**: Accepted
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**Date**: 2026-03
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## Context
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Federated nodes need to communicate directly for state sync, app deployment, and peer verification. Options: direct IP, VPN tunnel, Tor hidden services, I2P.
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## Decision
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Use Tor hidden services (.onion addresses) for all inter-node communication.
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## Consequences
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### Positive
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- **NAT traversal**: Works behind any firewall or NAT without port forwarding
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- **IP privacy**: Nodes never expose their real IP addresses to each other
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- **End-to-end encryption**: Tor provides encryption without additional TLS setup
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- **Censorship resistance**: Onion routing makes traffic analysis difficult
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- **Stable addressing**: .onion addresses persist across IP changes and network migrations
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- **No central infrastructure**: No VPN server, STUN/TURN server, or relay needed
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### Negative
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- **Latency**: Tor adds 200-500ms per hop; 3 hops per direction = noticeable delay
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- **Bandwidth**: Tor network has limited bandwidth; not suitable for bulk data transfer
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- **Reliability**: Tor circuits can break; connections may need retry logic
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- **Setup complexity**: Requires running a Tor daemon (`archy-tor` container)
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- **Blocked networks**: Some networks block Tor; bridges can help but add complexity
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### Mitigation
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- Use Tor only for RPC/control plane; bulk data (container images) pulled from registries
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- Implement retry with backoff for Tor connections
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- Container `archy-tor` runs automatically with host networking for hidden service access
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- Federation sync interval (5 min) tolerates occasional connection failures
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