{
  "$schema": "../../schema/test-vector.schema.json",
  "name": "ECDH Shared Secret (X25519)",
  "spec_ref": "src/15-identity.md",
  "protocol_version": 0,
  "description": "X25519 ECDH key exchange test vectors. MeshCore uses Ed25519 keys transposed to X25519 for key exchange. The resulting 32-byte shared secret is used as: AES key (bytes 0-15) and HMAC key (bytes 0-31).",
  "vectors": [
    {
      "id": "ecdh-001",
      "description": "RFC 7748 Test Vector: X25519 key exchange (Alice's perspective)",
      "type": "encode_decode",
      "structured": {
        "header": {
          "version": 0,
          "payload_type": "raw_custom",
          "route_type": "flood"
        },
        "path": {
          "hash_size": 1,
          "hash_count": 0,
          "hashes": []
        },
        "payload": {
          "data": "4A5D9D5BA4CE2DE1728E3BF480350F25E07E21C947D19E3376F09B3C1E161742"
        }
      },
      "binary": "3D 00 4A5D9D5BA4CE2DE1728E3BF480350F25E07E21C947D19E3376F09B3C1E161742",
      "crypto_context": {
        "sender_private_key": "77076D0A7318A57D3C16C17251B26645DF4C2F87EBC0992AB177FBA51DB92C2A",
        "recipient_public_key": "DE9EDB7D7B7DC1B4D35B61C2ECE435373F8343C85B78674DADFC7E146F882B4F"
      },
      "notes": "RFC 7748 Section 6.1. Alice's private key and Bob's public key produce the shared secret. Note: MeshCore transposes Ed25519 keys to X25519, so actual ECDH inputs differ from raw Ed25519 keys."
    },
    {
      "id": "ecdh-002",
      "description": "RFC 7748 Test Vector: X25519 key exchange (Bob's perspective)",
      "type": "encode_decode",
      "structured": {
        "header": {
          "version": 0,
          "payload_type": "raw_custom",
          "route_type": "flood"
        },
        "path": {
          "hash_size": 1,
          "hash_count": 0,
          "hashes": []
        },
        "payload": {
          "data": "4A5D9D5BA4CE2DE1728E3BF480350F25E07E21C947D19E3376F09B3C1E161742"
        }
      },
      "binary": "3D 00 4A5D9D5BA4CE2DE1728E3BF480350F25E07E21C947D19E3376F09B3C1E161742",
      "crypto_context": {
        "sender_private_key": "5DAB087E624A8A4B79E17F8B83800EE66F3BB1292618B6FD1C2F8B27FF88E0EB",
        "recipient_public_key": "8520F0098930A754748B7DDCB43EF75A0DBF3A0D26381AF4EBA4A98EAA9B4E6A"
      },
      "notes": "RFC 7748 Section 6.1. Bob's private key and Alice's public key produce the same shared secret as ecdh-001, verifying the commutative property of ECDH."
    },
    {
      "id": "ecdh-003",
      "description": "X25519 with all-zeros private key scalar (edge case)",
      "type": "encode_decode",
      "structured": {
        "header": {
          "version": 0,
          "payload_type": "raw_custom",
          "route_type": "flood"
        },
        "path": {
          "hash_size": 1,
          "hash_count": 0,
          "hashes": []
        },
        "payload": {
          "data": "0000000000000000000000000000000000000000000000000000000000000000"
        }
      },
      "binary": "3D 00 0000000000000000000000000000000000000000000000000000000000000000",
      "crypto_context": {
        "sender_private_key": "0000000000000000000000000000000000000000000000000000000000000000",
        "recipient_public_key": "DE9EDB7D7B7DC1B4D35B61C2ECE435373F8343C85B78674DADFC7E146F882B4F"
      },
      "notes": "Edge case: all-zero private key after clamping becomes a low-order scalar. X25519 with a clamped all-zero key (which becomes 0x40...00) against any public key. The all-zero shared secret indicates this is a degenerate key and implementations SHOULD reject it."
    }
  ]
}