7. Appendix A: header.fbs¶

include "recipients.fbs";

namespace ee.cyber.cdoc2.fbs.header;

// Union for communicating the recipient type
union Capsule {
    recipients.ECCPublicKeyCapsule,
    recipients.RSAPublicKeyCapsule,
    recipients.KeyServerCapsule,
    recipients.SymmetricKeyCapsule,
    recipients.PBKDF2Capsule,
    recipients.KeySharesCapsule
}

// FMK encryption method enum.
enum FMKEncryptionMethod:byte {
    UNKNOWN,
    XOR
}

// Payload encryption method enum.
enum PayloadEncryptionMethod:byte {
    UNKNOWN,
    CHACHA20POLY1305
}

// Intermediate record, some languages act very poorly when it comes
// to an array of unions.
// Thus it is better to have an an array of tables that
// contains the union as a field.
table RecipientRecord {
    capsule:                Capsule;
    key_label:              string (required);
    encrypted_fmk:          [ubyte] (required);
    fmk_encryption_method:  FMKEncryptionMethod = UNKNOWN;
}

// Header structure.
table Header {
    recipients:                [RecipientRecord];

    payload_encryption_method: PayloadEncryptionMethod = UNKNOWN;
}

root_type Header;