diff --git a/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module.go b/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module.go
index 915c6b66..5066da6b 100644
--- a/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module.go
+++ b/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module.go
@@ -59,6 +59,9 @@ func (m *integrationTesterModule) handleRequest(authReq *authRequest, r *Request
 		case SerializableStringConvRequest:
 			args = append(args, reflect.ValueOf(
 				pam.NewStringConvRequest(v.Style, v.Request)))
+		case SerializableBinaryConvRequest:
+			args = append(args, reflect.ValueOf(
+				pam.NewBinaryConvRequestFromBytes(v.Request)))
 		default:
 			if arg == nil {
 				args = append(args, reflect.Zero(method.Type().In(i)))
@@ -75,6 +78,13 @@ func (m *integrationTesterModule) handleRequest(authReq *authRequest, r *Request
 		case pam.StringConvResponse:
 			res.ActionArgs = append(res.ActionArgs,
 				SerializableStringConvResponse{value.Style(), value.Response()})
+		case pam.BinaryConvResponse:
+			data, err := value.Decode(utils.TestBinaryDataDecoder)
+			if err != nil {
+				return nil, err
+			}
+			res.ActionArgs = append(res.ActionArgs,
+				SerializableBinaryConvResponse{data})
 		case pam.Status:
 			authReq.lastError = value
 			res.ActionArgs = append(res.ActionArgs, value)
diff --git a/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module_test.go b/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module_test.go
index 3030e22f..41d3f29f 100644
--- a/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module_test.go
+++ b/cmd/pam-moduler/tests/integration-tester-module/integration-tester-module_test.go
@@ -72,6 +72,19 @@ func ensureEnv(tx *pam.Transaction, variable string, expected string) error {
 	}
 }
 
+func (r *Request) toBytes(t *testing.T) []byte {
+	if bytes, err := r.GOB(); err != nil {
+		t.Fatalf("error: %v", err)
+		return nil
+	} else {
+		return bytes
+	}
+}
+
+func (r *Request) toTransactionData(t *testing.T) []byte {
+	return utils.TestBinaryDataEncoder(r.toBytes(t))
+}
+
 func Test_Moduler_IntegrationTesterModule(t *testing.T) {
 	if !pam.CheckPamHasStartConfdir() {
 		t.Skip("this requires PAM with Conf dir support")
@@ -854,6 +867,107 @@ func Test_Moduler_IntegrationTesterModule(t *testing.T) {
 				},
 			},
 		},
+		"start-conv-binary": {
+			expectedStatus: pam.Success,
+			credentials: utils.NewBinaryTransactionWithData([]byte(
+				"\x00This is a binary data request\xC5\x00\xffYes it is!"),
+				[]byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99}),
+			checkedRequests: []checkedRequest{
+				{
+					r: NewRequest("StartConv", SerializableBinaryConvRequest{
+						utils.TestBinaryDataEncoder(
+							[]byte("\x00This is a binary data request\xC5\x00\xffYes it is!")),
+					}),
+					exp: []interface{}{SerializableBinaryConvResponse{
+						[]byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+					}, nil},
+				},
+				{
+					r: NewRequest("StartBinaryConv",
+						utils.TestBinaryDataEncoder(
+							[]byte("\x00This is a binary data request\xC5\x00\xffYes it is!"))),
+					exp: []interface{}{SerializableBinaryConvResponse{
+						[]byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+					}, nil},
+				},
+			},
+		},
+		"start-conv-binary-handle-failure-passed-data-mismatch": {
+			expectedStatus: pam.ConvErr,
+			credentials: utils.NewBinaryTransactionWithData([]byte(
+				"\x00This is a binary data request\xC5\x00\xffYes it is!"),
+				[]byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99}),
+			checkedRequests: []checkedRequest{
+				{
+					r: NewRequest("StartConv", SerializableBinaryConvRequest{
+						(&Request{"Not the expected binary data", nil}).toTransactionData(t),
+					}),
+					exp: []interface{}{nil, pam.ConvErr},
+				},
+				{
+					r: NewRequest("StartBinaryConv",
+						(&Request{"Not the expected binary data", nil}).toTransactionData(t)),
+					exp: []interface{}{nil, pam.ConvErr},
+				},
+			},
+		},
+		"start-conv-binary-handle-failure-returned-data-mismatch": {
+			expectedStatus: pam.ConvErr,
+			credentials: utils.NewBinaryTransactionWithRandomData(100,
+				[]byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99}),
+			checkedRequests: []checkedRequest{
+				{
+					r: NewRequest("StartConv", SerializableBinaryConvRequest{
+						(&Request{"Wrong binary data", nil}).toTransactionData(t),
+					}),
+					exp: []interface{}{nil, pam.ConvErr},
+				},
+				{
+					r: NewRequest("StartBinaryConv",
+						(&Request{"Wrong binary data", nil}).toTransactionData(t)),
+					exp: []interface{}{nil, pam.ConvErr},
+				},
+			},
+		},
+		"start-conv-binary-in-nil": {
+			expectedStatus: pam.Success,
+			credentials: utils.NewBinaryTransactionWithData(nil,
+				(&Request{"Binary data", []interface{}{true, 123, 0.5, "yay!"}}).toBytes(t)),
+			checkedRequests: []checkedRequest{
+				{
+					r: NewRequest("StartConv", SerializableBinaryConvRequest{}),
+					exp: []interface{}{SerializableBinaryConvResponse{
+						(&Request{"Binary data", []interface{}{true, 123, 0.5, "yay!"}}).toBytes(t),
+					}, nil},
+				},
+				{
+					r: NewRequest("StartBinaryConv", nil),
+					exp: []interface{}{SerializableBinaryConvResponse{
+						(&Request{"Binary data", []interface{}{true, 123, 0.5, "yay!"}}).toBytes(t),
+					}, nil},
+				},
+			},
+		},
+		"start-conv-binary-out-nil": {
+			expectedStatus: pam.Success,
+			credentials: utils.NewBinaryTransactionWithData([]byte(
+				"\x00This is a binary data request\xC5\x00\xffGimme nil!"), nil),
+			checkedRequests: []checkedRequest{
+				{
+					r: NewRequest("StartConv", SerializableBinaryConvRequest{
+						utils.TestBinaryDataEncoder(
+							[]byte("\x00This is a binary data request\xC5\x00\xffGimme nil!")),
+					}),
+					exp: []interface{}{SerializableBinaryConvResponse{}, nil},
+				},
+				{
+					r: NewRequest("StartBinaryConv",
+						utils.TestBinaryDataEncoder(
+							[]byte("\x00This is a binary data request\xC5\x00\xffGimme nil!"))),
+					exp: []interface{}{SerializableBinaryConvResponse{}, nil},
+				},
+			},
+		},
 	}
 
 	for name, tc := range tests {
@@ -1119,6 +1233,15 @@ func Test_Moduler_IntegrationTesterModule_Authenticate(t *testing.T) {
 				exp: []interface{}{nil, pam.SystemErr},
 			}},
 		},
+		"StartConv-Binary": {
+			expectedStatus: pam.SystemErr,
+			checkedRequests: []checkedRequest{{
+				r: NewRequest("StartConv", SerializableBinaryConvRequest{
+					[]byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+				}),
+				exp: []interface{}{nil, pam.SystemErr},
+			}},
+		},
 	}
 
 	for name, tc := range tests {
diff --git a/cmd/pam-moduler/tests/integration-tester-module/serialization.go b/cmd/pam-moduler/tests/integration-tester-module/serialization.go
index 78d734a0..13c870e7 100644
--- a/cmd/pam-moduler/tests/integration-tester-module/serialization.go
+++ b/cmd/pam-moduler/tests/integration-tester-module/serialization.go
@@ -30,6 +30,14 @@ type SerializableStringConvResponse struct {
 	Response string
 }
 
+type SerializableBinaryConvRequest struct {
+	Request []byte
+}
+
+type SerializableBinaryConvResponse struct {
+	Response []byte
+}
+
 func init() {
 	gob.Register(map[string]string{})
 	gob.Register(Request{})
@@ -43,5 +51,9 @@ func init() {
 		SerializableStringConvRequest{})
 	gob.RegisterName("main.SerializableStringConvResponse",
 		SerializableStringConvResponse{})
+	gob.RegisterName("main.SerializableBinaryConvRequest",
+		SerializableBinaryConvRequest{})
+	gob.RegisterName("main.SerializableBinaryConvResponse",
+		SerializableBinaryConvResponse{})
 	gob.Register(utils.SerializableError{})
 }
diff --git a/cmd/pam-moduler/tests/internal/utils/test-utils.go b/cmd/pam-moduler/tests/internal/utils/test-utils.go
index d7a39962..3b7f1f75 100644
--- a/cmd/pam-moduler/tests/internal/utils/test-utils.go
+++ b/cmd/pam-moduler/tests/internal/utils/test-utils.go
@@ -1,7 +1,14 @@
 package utils
 
+//#include <stdint.h>
+import "C"
+
 import (
+	"crypto/rand"
+	"encoding/binary"
 	"fmt"
+	"reflect"
+	"unsafe"
 
 	"github.com/msteinert/pam"
 )
@@ -148,3 +155,80 @@ func (c Credentials) RespondPAM(s pam.Style, msg string) (string, error) {
 	return "", pam.NewTransactionError(
 		&SerializableError{fmt.Sprintf("unhandled style: %v", s)}, pam.ConvErr)
 }
+
+type BinaryTransaction struct {
+	data         []byte
+	ExpectedNull bool
+	ReturnedData []byte
+}
+
+func TestBinaryDataEncoder(bytes []byte) []byte {
+	if len(bytes) > 0xff {
+		panic("Binary transaction size not supported")
+	}
+
+	if bytes == nil {
+		return bytes
+	}
+
+	data := make([]byte, 0, len(bytes)+1)
+	data = append(data, byte(len(bytes)))
+	data = append(data, bytes...)
+	return data
+}
+
+func TestBinaryDataDecoder(ptr pam.BinaryPointer) ([]byte, error) {
+	if ptr == nil {
+		return nil, nil
+	}
+
+	length := uint8(*((*C.uint8_t)(ptr)))
+	return C.GoBytes(unsafe.Pointer(ptr), C.int(length+1))[1:], nil
+}
+
+func NewBinaryTransactionWithData(data []byte, retData []byte) BinaryTransaction {
+	t := BinaryTransaction{ReturnedData: retData}
+	t.data = TestBinaryDataEncoder(data)
+	t.ExpectedNull = data == nil
+	return t
+}
+
+func NewBinaryTransactionWithRandomData(size uint8, retData []byte) BinaryTransaction {
+	t := BinaryTransaction{ReturnedData: retData}
+	randomData := make([]byte, size)
+	if err := binary.Read(rand.Reader, binary.LittleEndian, &randomData); err != nil {
+		panic(err)
+	}
+
+	t.data = TestBinaryDataEncoder(randomData)
+	return t
+}
+
+func (b BinaryTransaction) Data() []byte {
+	return b.data
+}
+
+func (b BinaryTransaction) RespondPAM(s pam.Style, msg string) (string, error) {
+	return "", pam.NewTransactionError(
+		&SerializableError{"unexpected non-binary request"}, pam.ConvErr)
+}
+
+func (b BinaryTransaction) RespondPAMBinary(ptr pam.BinaryPointer) ([]byte, error) {
+	if ptr == nil && !b.ExpectedNull {
+		return nil, pam.NewTransactionError(
+			&SerializableError{"unexpected null binary data"}, pam.ConvErr)
+	} else if ptr == nil {
+		return TestBinaryDataEncoder(b.ReturnedData), nil
+	}
+
+	bytes, _ := TestBinaryDataDecoder(ptr)
+	if !reflect.DeepEqual(bytes, b.data[1:]) {
+		return nil, pam.NewTransactionError(
+			&SerializableError{
+				fmt.Sprintf("data mismatch %v vs %v", bytes, b.data[1:]),
+			},
+			pam.ConvErr)
+	}
+
+	return TestBinaryDataEncoder(b.ReturnedData), nil
+}
diff --git a/module-transaction-mock.go b/module-transaction-mock.go
index a702e641..e2b5b8b1 100644
--- a/module-transaction-mock.go
+++ b/module-transaction-mock.go
@@ -10,7 +10,9 @@ void init_pam_conv(struct pam_conv *conv, uintptr_t appdata);
 */
 import "C"
 import (
+	"errors"
 	"fmt"
+	"reflect"
 	"runtime"
 	"runtime/cgo"
 	"testing"
@@ -131,8 +133,11 @@ type mockConversationHandler struct {
 	PromptEchoOff           string
 	TextInfo                string
 	ErrorMsg                string
+	Binary                  []byte
 	ExpectedMessage         string
 	ExpectedMessagesByStyle map[Style]string
+	ExpectedNil             bool
+	ExpectedBinary          []byte
 	CheckEmptyMessage       bool
 	ExpectedStyle           Style
 	CheckZeroStyle          bool
@@ -175,3 +180,45 @@ func (c mockConversationHandler) RespondPAM(s Style, msg string) (string, error)
 	return "", NewTransactionError(
 		fmt.Errorf("unhandled style: %v", s), ConvErr)
 }
+
+func testBinaryDataEncoder(bytes []byte) []byte {
+	if len(bytes) > 0xff {
+		panic("Binary transaction size not supported")
+	}
+
+	if bytes == nil {
+		return bytes
+	}
+
+	data := make([]byte, 0, len(bytes)+1)
+	data = append(data, byte(len(bytes)))
+	data = append(data, bytes...)
+	return data
+}
+
+func testBinaryDataDecoder(ptr BinaryPointer) ([]byte, error) {
+	if ptr == nil {
+		return nil, nil
+	}
+
+	length := uint8(*((*C.uint8_t)(ptr)))
+	return C.GoBytes(unsafe.Pointer(ptr), C.int(length+1))[1:], nil
+}
+
+func (m mockConversationHandler) RespondPAMBinary(ptr BinaryPointer) ([]byte, error) {
+	if ptr == nil && !m.ExpectedNil {
+		return nil, NewTransactionError(
+			errors.New("unexpected null binary data"), ConvErr)
+	} else if ptr == nil {
+		return testBinaryDataEncoder(m.Binary), nil
+	}
+
+	bytes, _ := testBinaryDataDecoder(ptr)
+	if !reflect.DeepEqual(bytes, m.ExpectedBinary) {
+		return nil, NewTransactionError(
+			fmt.Errorf("data mismatch %v vs %v", bytes, m.ExpectedBinary),
+			ConvErr)
+	}
+
+	return testBinaryDataEncoder(m.Binary), nil
+}
diff --git a/module-transaction.go b/module-transaction.go
index 5731a5af..e5fff009 100644
--- a/module-transaction.go
+++ b/module-transaction.go
@@ -18,6 +18,7 @@ import "C"
 import (
 	"errors"
 	"fmt"
+	"runtime"
 	"runtime/cgo"
 	"sync/atomic"
 	"unsafe"
@@ -242,6 +243,74 @@ func (s stringConvResponse) Response() string {
 	return s.response
 }
 
+// BinaryConvRequest is a ConvRequest for performing binary conversations.
+type BinaryConvRequest struct {
+	ptr BinaryPointer
+}
+
+// NewBinaryConvRequest creates a new BinaryConvRequest.
+func NewBinaryConvRequest(ptr BinaryPointer) BinaryConvRequest {
+	return BinaryConvRequest{ptr}
+}
+
+// NewBinaryConvRequest creates a new BinaryConvRequest from an array
+// pointer, the lifetime of the data is bound to the object.
+func NewBinaryConvRequestFromBytes(bytes []byte) BinaryConvRequest {
+	m := BinaryConvRequest{}
+	if bytes != nil {
+		m.ptr = BinaryPointer(C.CBytes(bytes))
+		runtime.SetFinalizer(&m, func(*BinaryConvRequest) {
+			defer C.free(unsafe.Pointer(m.ptr))
+			m.ptr = nil
+		})
+	}
+	return m
+}
+
+// Style returns the response style for the request, so always BinaryPrompt.
+func (b BinaryConvRequest) Style() Style {
+	return BinaryPrompt
+}
+
+// Pointer returns the conversation style of the StringConvRequest.
+func (b BinaryConvRequest) Pointer() BinaryPointer {
+	return b.ptr
+}
+
+type BinaryDecoder func(BinaryPointer) ([]byte, error)
+
+// BinaryConvResponse is a subtype of ConvResponse used for binary
+// conversation responses.
+type BinaryConvResponse interface {
+	ConvResponse
+	Data() BinaryPointer
+	Decode(BinaryDecoder) ([]byte, error)
+}
+
+type binaryConvResponse struct {
+	ptr BinaryPointer
+}
+
+// Style returns the response style for the response, so always BinaryPrompt.
+func (b binaryConvResponse) Style() Style {
+	return BinaryPrompt
+}
+
+// Data returns the response native pointer, it's up to the protocol to parse
+// it accordingly.
+func (b binaryConvResponse) Data() BinaryPointer {
+	return b.ptr
+}
+
+// Decode decodes the binary data using the provided decoder function.
+func (b binaryConvResponse) Decode(decoder BinaryDecoder) (
+	[]byte, error) {
+	if decoder == nil {
+		return nil, errors.New("nil decoder provided")
+	}
+	return decoder(b.ptr)
+}
+
 // StartStringConv starts a text-based conversation using the provided style
 // and prompt.
 func (m *ModuleTransaction) StartStringConv(style Style, prompt string) (
@@ -273,6 +342,24 @@ func (m *ModuleTransaction) StartStringConvf(style Style, format string, args ..
 	return m.StartStringConv(style, fmt.Sprintf(format, args...))
 }
 
+// StartBinaryConv starts a binary conversation using the provided bytes.
+func (m *ModuleTransaction) StartBinaryConv(bytes []byte) (
+	BinaryConvResponse, error) {
+	return m.startBinaryConvImpl(m, bytes)
+}
+
+func (m *ModuleTransaction) startBinaryConvImpl(iface moduleTransactionIface,
+	bytes []byte) (
+	BinaryConvResponse, error) {
+	res, err := m.startConvImpl(iface, NewBinaryConvRequestFromBytes(bytes))
+	if err != nil {
+		return nil, err
+	}
+
+	binaryRes := res.(BinaryConvResponse)
+	return binaryRes, nil
+}
+
 // StartConv initiates a PAM conversation using the provided ConvRequest.
 func (m *ModuleTransaction) StartConv(req ConvRequest) (
 	ConvResponse, error) {
@@ -332,6 +419,14 @@ func (m *ModuleTransaction) startConvMultiImpl(iface moduleTransactionIface,
 		case StringConvRequest:
 			cBytes = unsafe.Pointer(C.CString(r.Prompt()))
 			defer C.free(unsafe.Pointer(cBytes))
+		case BinaryConvRequest:
+			if !CheckPamHasBinaryProtocol() {
+				return nil, NewTransactionError(
+					fmt.Errorf(
+						"binary protocol is not supported"),
+					ConvErr)
+			}
+			cBytes = unsafe.Pointer(r.Pointer())
 		default:
 			return nil, NewTransactionError(
 				fmt.Errorf(
@@ -374,6 +469,14 @@ func (m *ModuleTransaction) startConvMultiImpl(iface moduleTransactionIface,
 				style:    msgStyle,
 				response: C.GoString(resp.resp),
 			})
+		case BinaryPrompt:
+			// Let's steal the resp ownership in this case
+			bcr := binaryConvResponse{BinaryPointer(resp.resp)}
+			responses[i].resp = nil
+			runtime.SetFinalizer(&bcr, func(bcr *binaryConvResponse) {
+				C.free(unsafe.Pointer(bcr.ptr))
+			})
+			goReplies = append(goReplies, bcr)
 		default:
 			return nil, NewTransactionError(
 				fmt.Errorf(
diff --git a/module-transaction_test.go b/module-transaction_test.go
index 751f9682..887b4276 100644
--- a/module-transaction_test.go
+++ b/module-transaction_test.go
@@ -99,6 +99,8 @@ func Test_NewNullModuleTransaction(t *testing.T) {
 				return mt.StartConvMulti([]ConvRequest{
 					NewStringConvRequest(TextInfo, "a prompt"),
 					NewStringConvRequest(ErrorMsg, "another prompt"),
+					NewBinaryConvRequest(BinaryPointer(&mt)),
+					NewBinaryConvRequestFromBytes([]byte("These are bytes!")),
 				})
 			},
 		},
@@ -592,31 +594,226 @@ func Test_MockModuleTransaction(t *testing.T) {
 		},
 		"StartConvMulti-all-types": {
 			expectedRet: Success,
-			expectedValue: []ConvResponse{
-				stringConvResponse{TextInfo, "nice to see you, Go!"},
-				stringConvResponse{ErrorMsg, "ops, sorry..."},
-				stringConvResponse{PromptEchoOn, "here's my public data"},
-				stringConvResponse{PromptEchoOff, "here's my private data"},
+			expectedValue: []any{
+				[]ConvResponse{
+					stringConvResponse{TextInfo, "nice to see you, Go!"},
+					stringConvResponse{ErrorMsg, "ops, sorry..."},
+					stringConvResponse{PromptEchoOn, "here's my public data"},
+					stringConvResponse{PromptEchoOff, "here's my private data"},
+				},
+				[][]byte{
+					{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+				},
 			},
 			conversationHandler: mockConversationHandler{
 				TextInfo:      "nice to see you, Go!",
 				ErrorMsg:      "ops, sorry...",
 				PromptEchoOn:  "here's my public data",
 				PromptEchoOff: "here's my private data",
+				Binary:        []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
 				ExpectedMessagesByStyle: map[Style]string{
 					TextInfo:      "hello PAM!",
 					ErrorMsg:      "This is wrong, PAM!",
 					PromptEchoOn:  "Give me your non-private infos",
 					PromptEchoOff: "Give me your private secrets",
 				},
+				ExpectedBinary: []byte("\x00This is a binary data request\xC5\x00\xffYes it is!"),
 			},
 			testFunc: func(mock *mockModuleTransaction) (any, error) {
-				return mt.startConvMultiImpl(mock, []ConvRequest{
+				requests := []ConvRequest{
 					NewStringConvRequest(TextInfo, "hello PAM!"),
 					NewStringConvRequest(ErrorMsg, "This is wrong, PAM!"),
 					NewStringConvRequest(PromptEchoOn, "Give me your non-private infos"),
 					NewStringConvRequest(PromptEchoOff, "Give me your private secrets"),
-				})
+					NewBinaryConvRequestFromBytes(
+						testBinaryDataEncoder([]byte("\x00This is a binary data request\xC5\x00\xffYes it is!"))),
+				}
+
+				if data, err := mt.startConvMultiImpl(mock, requests); err != nil {
+					return data, err
+				} else {
+					stringResponses := []ConvResponse{}
+					binaryResponses := [][]byte{}
+					for i, r := range data {
+						if r.Style() != requests[i].Style() {
+							mock.T.Fatalf("unexpected style %v vs %v",
+								r.Style(), requests[i].Style())
+						}
+
+						switch rt := r.(type) {
+						case BinaryConvResponse:
+							decoded, err := rt.Decode(testBinaryDataDecoder)
+							if err != nil {
+								return data, err
+							}
+							binaryResponses = append(binaryResponses, decoded)
+						case StringConvResponse:
+							stringResponses = append(stringResponses, r)
+						default:
+							mock.T.Fatalf("unexpected value %v", rt)
+						}
+					}
+					return []any{
+						stringResponses,
+						binaryResponses,
+					}, err
+				}
+			},
+		},
+		"StartConv-Binary": {
+			expectedRet:   Success,
+			expectedValue: []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x00This is a binary data request\xC5\x00\xffYes it is!"),
+				Binary:         []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				bytes := testBinaryDataEncoder([]byte(
+					"\x00This is a binary data request\xC5\x00\xffYes it is!"))
+				if data, err := mt.startConvImpl(mock, NewBinaryConvRequestFromBytes(bytes)); err != nil {
+					return data, err
+				} else {
+					return data.(BinaryConvResponse).Decode(testBinaryDataDecoder)
+				}
+			},
+		},
+		"StartConv-Binary-expected-data-mismatch": {
+			expectedRet:   ConvErr,
+			expectedValue: nil,
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x00This is not the expected data!"),
+				Binary:         []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				bytes := testBinaryDataEncoder([]byte(
+					"\x00This is a binary data request\xC5\x00\xffYes it is!"))
+				return mt.startConvImpl(mock, NewBinaryConvRequestFromBytes(bytes))
+			},
+		},
+		"StartConv-Binary-unexpected-nil": {
+			expectedRet:   ConvErr,
+			expectedValue: nil,
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x00This should not be nil"),
+				Binary:         []byte("\x1ASome binary Dat\xaa"),
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				return mt.startConvImpl(mock, NewBinaryConvRequestFromBytes(nil))
+			},
+		},
+		"StartConv-Binary-expected-nil": {
+			expectedRet:   Success,
+			expectedValue: []byte("\x1ASome binary Dat\xaa"),
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedNil:    true,
+				ExpectedBinary: []byte("\x00This should not be nil"),
+				Binary:         []byte("\x1ASome binary Dat\xaa"),
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				if data, err := mt.startConvImpl(mock, NewBinaryConvRequestFromBytes(nil)); err != nil {
+					return data, err
+				} else {
+					return data.(BinaryConvResponse).Decode(testBinaryDataDecoder)
+				}
+			},
+		},
+		"StartConv-Binary-returns-nil": {
+			expectedRet:   Success,
+			expectedValue: BinaryPointer(nil),
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x1ASome binary Dat\xaa"),
+				Binary:         nil,
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				bytes := testBinaryDataEncoder([]byte("\x1ASome binary Dat\xaa"))
+				if data, err := mt.startConvImpl(mock, NewBinaryConvRequestFromBytes(bytes)); err != nil {
+					return data, err
+				} else {
+					return data.(BinaryConvResponse).Data(), err
+				}
+			},
+		},
+		"StartBinaryConv": {
+			expectedRet:   Success,
+			expectedValue: []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x00This is a binary data request\xC5\x00\xffYes it is!"),
+				Binary:         []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				bytes := testBinaryDataEncoder([]byte(
+					"\x00This is a binary data request\xC5\x00\xffYes it is!"))
+				if data, err := mt.startConvImpl(mock, NewBinaryConvRequestFromBytes(bytes)); err != nil {
+					return data, err
+				} else {
+					return data.(BinaryConvResponse).Decode(testBinaryDataDecoder)
+				}
+			},
+		},
+		"StartBinaryConv-expected-data-mismatch": {
+			expectedRet:   ConvErr,
+			expectedValue: nil,
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x00This is not the expected data!"),
+				Binary:         []byte{0x01, 0x02, 0x03, 0x05, 0x00, 0x99},
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				bytes := testBinaryDataEncoder([]byte(
+					"\x00This is a binary data request\xC5\x00\xffYes it is!"))
+				return mt.startBinaryConvImpl(mock, bytes)
+			},
+		},
+		"StartBinaryConv-unexpected-nil": {
+			expectedRet:   ConvErr,
+			expectedValue: nil,
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x00This should not be nil"),
+				Binary:         []byte("\x1ASome binary Dat\xaa"),
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				return mt.startBinaryConvImpl(mock, nil)
+			},
+		},
+		"StartBinaryConv-expected-nil": {
+			expectedRet:   Success,
+			expectedValue: []byte("\x1ASome binary Dat\xaa"),
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedNil:    true,
+				ExpectedBinary: []byte("\x00This should not be nil"),
+				Binary:         []byte("\x1ASome binary Dat\xaa"),
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				if data, err := mt.startBinaryConvImpl(mock, nil); err != nil {
+					return data, err
+				} else {
+					return data.Decode(testBinaryDataDecoder)
+				}
+			},
+		},
+		"StartBinaryConv-returns-nil": {
+			expectedRet:   Success,
+			expectedValue: BinaryPointer(nil),
+			conversationHandler: mockConversationHandler{
+				ExpectedStyle:  BinaryPrompt,
+				ExpectedBinary: []byte("\x1ASome binary Dat\xaa"),
+				Binary:         nil,
+			},
+			testFunc: func(mock *mockModuleTransaction) (any, error) {
+				bytes := testBinaryDataEncoder([]byte("\x1ASome binary Dat\xaa"))
+				if data, err := mt.startBinaryConvImpl(mock, bytes); err != nil {
+					return data, err
+				} else {
+					return data.Data(), err
+				}
 			},
 		},
 	}
diff --git a/transaction.c b/transaction.c
index 5c8c33c4..842ce8f1 100644
--- a/transaction.c
+++ b/transaction.c
@@ -30,7 +30,10 @@ int cb_pam_conv(int num_msg, PAM_CONST struct pam_message **msg, struct pam_resp
 error:
 	for (size_t i = 0; i < num_msg; ++i) {
 		if ((*resp)[i].resp) {
-			memset((*resp)[i].resp, 0, strlen((*resp)[i].resp));
+#ifdef PAM_BINARY_PROMPT
+			if (msg[i]->msg_style != PAM_BINARY_PROMPT)
+#endif
+				memset((*resp)[i].resp, 0, strlen((*resp)[i].resp));
 			free((*resp)[i].resp);
 		}
 	}