89 lines
4.6 KiB
Markdown
89 lines
4.6 KiB
Markdown
# ChronoSeal Protocol Specification (PROTOCOL)
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This document defines the formal wire protocol, state transitions, cryptographic primitives, and execution invariants of the ChronoSeal browser attestation system.
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---
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## 1. Sequence Flow & Handshake
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ChronoSeal operates as a stateful, sequential challenge-response chain over HTTP/REST.
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```
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Client (JS/WASM) Server (chronoseald)
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| 1. POST /init { public_key: String } -----------------> |
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| | (Generates VM Opcodes)
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| | (Computes initial hash chain head H_0)
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| | (Saves initial session record)
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| <--- 200 OK { InitResponse } --------------------------|
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| [Client executes VM program & prepares gene preview] |
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| 2. POST /hb { HeartbeatRequest } ---------------------> |
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| | (Loads session & executes CAS check)
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| | (Verifies Ed25519 signature)
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| | (Validates VM stack-state parity)
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| | (Computes expected gene mutation)
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| | (Validates hash chain continuity H_N == expected)
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| | (Rotates salt & issues next mutation order)
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| <--- 200 OK { HeartbeatResponse } ---------------------| (Saves updated session record)
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```
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---
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## 2. Cryptographic Transition Mechanics
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### A. Handshake Phase (`/init`)
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The client registers a 32-byte Ed25519 verifying key represented as a hex string.
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The server:
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1. Generates a 32-byte session ID ($ID$) and a 16-byte initial salt ($S_0$).
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2. Computes the initial hash chain head:
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$$H_0 = \text{Blake3}(ID \parallel PK_{\text{client}} \parallel S_0)$$
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3. Generates a random VM program of size $8..=16$ bytes.
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4. Creates the initial mutation order program $M_1$.
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5. Persists the session record in the database.
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---
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### B. Heartbeat progression (`/hb`)
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For each heartbeat step $n \ge 1$:
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The client submits:
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* `prev_hash`: $H_{n-1}$ (hex encoded).
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* `timestamp`: $T_n$ (milliseconds).
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* `entropy_data`: Mouse movement arrays.
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* `stack_state`: The VM final stack and instruction pointer `ip` after execution.
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* `gene_commitment`: Hex-encoded commitment of the mutated gene state.
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* `signature`: Ed25519 signature of the canonical alphabetical JSON payload.
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The server:
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1. Loads the session record from storage, enforcing optimistic locking (CAS check) to confirm the database `last_hash` matches $H_{n-1}$.
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2. Validates the Ed25519 signature against the canonical alphabetical serialization.
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3. Re-executes the session's VM opcodes and asserts the client's `stack_state` matches the output.
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4. Applies the mutation order $M_n$ to the stored gene state and calculates the expected commitment:
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$$C_n = \text{Blake3}(\text{CandidateGene} \parallel ID \parallel n)$$
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Asserts the client's `gene_commitment` matches.
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5. Validates that $|T_{\text{server}} - T_n| \le \text{max\_drift}$.
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6. Advances the hash chain:
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$$H_n = \text{Blake3}(H_{n-1} \parallel T_n \parallel \text{Blake3}(E_n) \parallel \text{Blake3}(S_n) \parallel S_{n-1})$$
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7. Rotates the salt to $S_n$ and issues the next mutation order $M_{n+1}$.
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---
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## 3. VM Instruction Specification
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The client VM executes instructions sequentially. The instruction set consists of:
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* `0x00`: Pushes the next 4 bytes in the instruction stream onto the stack as a `u32` value (little-endian).
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* `0x01`..=`0x07`: Binary operators. Requires at least 2 elements on the stack:
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* `0x01`: Wrapping Add (`a.wrapping_add(b)`)
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* `0x02`: Wrapping Sub (`a.wrapping_sub(b)`)
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* `0x03`: Wrapping Mul (`a.wrapping_mul(b)`)
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* `0x04`: XOR (`a ^ b`)
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* `0x05`: AND (`a & b`)
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* `0x06`: OR (`a | b`)
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* `0x07`: Rotate Left (`a.rotate_left(b % 32)`)
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* `0x08`: Unary Bitwise Not (`!a`). Requires at least 1 element on the stack.
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* `0x09`: Hash Stack. Hashes all stack elements using BLAKE3 and reduces it to a single `u32` value, clearing the stack and pushing the hash.
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* *Any other opcode:* Terminates VM execution immediately.
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