特性五：传输加密

方案：使用 ALTS或TLS加密传输
grpc 框架内有实现相关代码：

服务端实现：

func (s *Server) handleRawConn(rawConn net.Conn) {
    if s.quit.HasFired() {
        rawConn.Close()
        return
    }
    rawConn.SetDeadline(time.Now().Add(s.opts.connectionTimeout))
    // 认证信息，tls或 alts服务解密
    conn, authInfo, err := s.useTransportAuthenticator(rawConn)
    if err != nil {
        // ErrConnDispatched means that the connection was dispatched away from
        // gRPC; those connections should be left open.
        if err != credentials.ErrConnDispatched {
            s.mu.Lock()
            s.errorf("ServerHandshake(%q) failed: %v", rawConn.RemoteAddr(), err)
            s.mu.Unlock()
            channelz.Warningf(s.channelzID, "grpc: Server.Serve failed to complete security handshake from %q: %v", rawConn.RemoteAddr(), err)
            rawConn.Close()
        }
        rawConn.SetDeadline(time.Time{})
        return
    }

客户端实现：

func newHTTP2Client(connectCtx, ctx context.Context, addr TargetInfo, opts ConnectOptions, onPrefaceReceipt func(), onGoAway func(GoAwayReason), onClose func()) (_ *http2Client, err error) {
    // 拨号连接
    conn, err := dial(connectCtx, opts.Dialer, addr.Addr)
    if err != nil {
        if opts.FailOnNonTempDialError {
            return nil, connectionErrorf(isTemporary(err), err, "transport: error while dialing: %v", err)
        }
        return nil, connectionErrorf(true, err, "transport: Error while dialing %v", err)
    }
    // ...
    // 有证书，则用https
    if transportCreds != nil {
        scheme = "https"
        conn, authInfo, err = transportCreds.ClientHandshake(connectCtx, addr.Authority, conn)
        if err != nil {
            return nil, connectionErrorf(isTemporary(err), err, "transport: authentication handshake failed: %v", err)
        }
        isSecure = true
    }
    //...
}

TLS为例：

使用方法：
服务端：

    // Create tls based credential.
    creds, err := credentials.NewServerTLSFromFile(testdata.Path("server1.pem"), testdata.Path("server1.key"))
    if err != nil {
        log.Fatalf("failed to create credentials: %v", err)
    }

    s := grpc.NewServer(grpc.Creds(creds))

client端：

// Create tls based credential.
    creds, err := credentials.NewClientTLSFromFile(testdata.Path("ca.pem"), "x.test.youtube.com")
    if err != nil {
        log.Fatalf("failed to load credentials: %v", err)
    }

    // Set up a connection to the server.
    conn, err := grpc.Dial(*addr, grpc.WithTransportCredentials(creds), grpc.WithBlock())
    if err != nil {
        log.Fatalf("did not connect: %v", err)
    }