swaitsandClaude Opus 4.7
f83d4088e3
Every "Test vectors: \`corpus/...\`" mention in the spec is now a markdown link pointing at the corresponding file or directory on GitHub. Each version build resolves its links to the correct git ref: - /latest/ -> https://github.com/swaits/meshcore-spec/tree/main/corpus/... - /v0.1.0/ -> https://github.com/swaits/meshcore-spec/tree/v0.1.0/corpus/... - future /vX.Y.Z/ -> /tree/vX.Y.Z/corpus/... Two changes: 1. src/*.md (18 files): the inline-code corpus paths in each "Cross-References" section are now markdown links. Directories point at /tree/main/corpus/..., individual .json files point at /blob/main/corpus/.... CHANGELOG and other non-corpus main links are intentionally left pointing at main — the canonical history lives there regardless of which version you're reading. 2. justfile: `cut-version` now also runs a sed over the snapshot's *.md files replacing /tree/main/corpus -> /tree/<VERSION>/corpus and /blob/main/corpus -> /blob/<VERSION>/corpus. So a freshly-cut version is self-consistent. versions/v0.1.0/* regenerated by re-running `just cut-version v0.1.0` after the new src/ links + recipe sed landed. Tagging the release commit (`git tag v0.1.0`) is now REQUIRED — not "optional" — because the rendered /v0.1.0/ pages reference /tree/v0.1.0/corpus/... on GitHub. Without the tag the links 404. cut-version's output now says so. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
75 lines
2.9 KiB
Markdown
75 lines
2.9 KiB
Markdown
# MeshCore Protocol Specification
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## Section 7: Payload — Anonymous Request
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### Overview
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The anonymous request payload allows a node to send an encrypted message to a
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recipient without the recipient needing to know the sender in advance. Instead of
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a 1-byte source hash, the full 32-byte Ed25519 public key of the sender is
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included, enabling the recipient to compute the shared secret for decryption.
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### Payload Type
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Header payload type field: `0x07` (ANON_REQ)
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### Wire Format
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```
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0
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| dest_hash(1) | |
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+-+-+-+-+-+-+-+-+ |
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| Sender Public Key (32 bytes) |
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| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Cipher MAC (2 bytes) | |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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| Ciphertext (N × 16 bytes, N ≥ 1) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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```
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### Fields
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| Field | Offset | Size | Type | Description |
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|-------|--------|------|------|-------------|
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| dest_hash | 0 | 1 byte | raw | First byte of recipient's Ed25519 public key |
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| sender_pub_key | 1 | 32 bytes | raw | Full Ed25519 public key of sender |
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| cipher_mac | 33 | 2 bytes | raw | Truncated HMAC-SHA256 over ciphertext |
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| ciphertext | 35 | variable (multiple of 16) | raw | AES-128-ECB encrypted data |
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### Minimum Size
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- Minimum payload: 1 + 32 + 2 + 16 = 51 bytes
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### Encryption
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1. Sender computes ECDH shared secret using its private key and the recipient's
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public key.
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2. Encrypt plaintext using AES-128-ECB with first 16 bytes of shared secret.
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3. Compute HMAC-SHA256 over ciphertext with full 32-byte shared secret.
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Truncate to 2 bytes.
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4. Assemble: dest_hash || sender_pub_key || MAC || ciphertext.
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### Decryption
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1. Read dest_hash. If it does not match this node, the packet is not for us
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(but MAY be forwarded).
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2. Read 32-byte sender_pub_key. Construct an Identity from it.
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3. Compute ECDH shared secret between this node's private key and sender's
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public key.
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4. Verify the MAC and decrypt as in [Section 14](14-crypto.md).
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### Cross-References
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- [Section 6: Encrypted Payloads](06-payload-encrypted.md) — Standard encrypted format
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- [Section 14: Cryptography](14-crypto.md) — Encrypt-then-MAC
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- [Section 15: Identity](15-identity.md) — ECDH key exchange
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- Test vectors: [`corpus/payloads/anon-req/`](https://github.com/swaits/meshcore-spec/tree/v0.1.0/corpus/payloads/anon-req/)
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### Reference Implementation
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- `Mesh::createAnonDatagram()` in `src/Mesh.cpp` — Encoding
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- `Mesh::onRecvPacket()`, case `PAYLOAD_TYPE_ANON_REQ` — Decoding
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