const (
    RatchetKeyMaxLifetime = time.Hour * 672

    // DoubleRatchetOverhead is the number of bytes the ratchet adds in ciphertext overhead.
    DoubleRatchetOverhead = 120
)

type KeyExchange struct {
    PublicKey      []byte
    IdentityPublic []byte
    Dh             []byte
    Dh1            []byte
}

type MessageKey struct {
    Num          uint32
    Key          []byte
    CreationTime int64
}

type Ratchet struct {
    TheirSigningPublic  [32]byte
    TheirIdentityPublic [32]byte
    MySigningPublic     [32]byte
    MySigningPrivate    [64]byte
    MyIdentityPrivate   [32]byte
    MyIdentityPublic    [32]byte

    // Now is an optional function that will be used to get the current
    // time. If nil, time.Now is used.
    Now func() time.Time
    // contains filtered or unexported fields
}

type RatchetState struct {
    TheirSigningPublic  []byte
    TheirIdentityPublic []byte
    MySigningPublic     []byte
    MySigningPrivate    []byte
    MyIdentityPrivate   []byte
    MyIdentityPublic    []byte
    SavedKeys           []*SavedKeys
    RootKey             []byte
    SendHeaderKey       []byte
    RecvHeaderKey       []byte
    NextSendHeaderKey   []byte
    NextRecvHeaderKey   []byte
    SendChainKey        []byte
    RecvChainKey        []byte
    SendRatchetPrivate  []byte
    RecvRatchetPublic   []byte
    SendCount           uint32
    RecvCount           uint32
    PrevSendCount       uint32
    Private0            []byte
    Private1            []byte
    Ratchet             bool
}

type SavedKeys struct {
    HeaderKey   []byte
    MessageKeys []*MessageKey
}

type SignedKeyExchange struct {
    Signed    []byte
    Signature []byte
}