// authResp generates the encrypted authentication response message.
func (h *encHandshake) authResp(prv *ecdsa.PrivateKey, token []byte) ([]byte, error) {
// responder auth message
// E(remote-pubk, ecdhe-random-pubk || nonce || 0x0)
resp := make([]byte, authRespLen)
n := copy(resp, exportPubkey(&h.randomPrivKey.PublicKey))
n += copy(resp[n:], h.respNonce)
if token == nil {
resp[n] = 0
} else {
resp[n] = 1
}
// encrypt using remote-pubk
return ecies.Encrypt(rand.Reader, h.remotePub, resp, nil, nil)
}
// authMsg creates an encrypted initiator handshake message.
func (h *encHandshake) authMsg(prv *ecdsa.PrivateKey, token []byte) ([]byte, error) {
var tokenFlag byte
if token == nil {
// no session token found means we need to generate shared secret.
// ecies shared secret is used as initial session token for new peers
// generate shared key from prv and remote pubkey
var err error
if token, err = h.ecdhShared(prv); err != nil {
return nil, err
}
} else {
// for known peers, we use stored token from the previous session
tokenFlag = 0x01
}
// sign known message:
// ecdh-shared-secret^nonce for new peers
// token^nonce for old peers
signed := xor(token, h.initNonce)
signature, err := crypto.Sign(signed, h.randomPrivKey.ExportECDSA())
if err != nil {
return nil, err
}
// encode auth message
// signature || sha3(ecdhe-random-pubk) || pubk || nonce || token-flag
msg := make([]byte, authMsgLen)
n := copy(msg, signature)
n += copy(msg[n:], crypto.Sha3(exportPubkey(&h.randomPrivKey.PublicKey)))
n += copy(msg[n:], crypto.FromECDSAPub(&prv.PublicKey)[1:])
n += copy(msg[n:], h.initNonce)
msg[n] = tokenFlag
// encrypt auth message using remote-pubk
return ecies.Encrypt(rand.Reader, h.remotePub, msg, nil, nil)
}
func Encrypt(pub *ecdsa.PublicKey, message []byte) ([]byte, error) {
return ecies.Encrypt(rand.Reader, ecies.ImportECDSAPublic(pub), message, nil, nil)
}