get_share_and_ticket — Group 15, Code 03

Preferred combined command: 32-byte share + optional 4-byte ticket.

Request command_data (after challenge)

Total 67 bytes (Appendix F.5):

cs_id[16] || key_id[1] || client_sn[5] || timestamp_be64[8] || client_nonce[16]
|| mail_denom[1] || mail_sn_be[4] || mail_an[16]

All-zero mail_an = anonymous: response ticket is 0.

Response body

share[32] || ticket_be32[4]   // 36 bytes

Derive K_rke by XOR of ≥13 shares then Expand-Only HKDF (RKE-EncryptionKey-v2.0).

Source: raidax/rke/rke_share_ticket.c.