diff --git a/_cmptest/_md5demo/md5.go b/_cmptest/_md5demo/md5.go
new file mode 100644
index 00000000..dbee9e66
--- /dev/null
+++ b/_cmptest/_md5demo/md5.go
@@ -0,0 +1,14 @@
+package main
+
+import (
+	"crypto/md5"
+	"fmt"
+	"io"
+)
+
+func main() {
+	h := md5.New()
+	io.WriteString(h, "The fog is getting thicker!")
+	io.WriteString(h, "And Leon's getting laaarger!")
+	fmt.Printf("%x", h.Sum(nil))
+}
diff --git a/_demo/cmd5demo/md5.go b/_demo/cmd5demo/md5.go
new file mode 100644
index 00000000..1c08a192
--- /dev/null
+++ b/_demo/cmd5demo/md5.go
@@ -0,0 +1,18 @@
+package main
+
+import (
+	"fmt"
+	"unsafe"
+
+	"github.com/goplus/llgo/c/openssl"
+)
+
+func main() {
+	var md5 openssl.MD5_CTX
+	var h = make([]byte, openssl.MD5_LBLOCK)
+	md5.Init()
+	md5.UpdateString("The fog is getting thicker!")
+	md5.UpdateString("And Leon's getting laaarger!")
+	md5.Final(unsafe.Pointer(unsafe.SliceData(h)))
+	fmt.Printf("%x", h)
+}
diff --git a/c/openssl/md5.go b/c/openssl/md5.go
new file mode 100644
index 00000000..b828da9f
--- /dev/null
+++ b/c/openssl/md5.go
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package openssl
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+// -----------------------------------------------------------------------------
+
+const (
+	MD5_CBLOCK = 64
+	MD5_LBLOCK = MD5_CBLOCK / 4
+)
+
+// -----------------------------------------------------------------------------
+
+type MD5_LONG = c.Uint
+
+type MD5_CTX struct {
+	A, B, C, D MD5_LONG
+	Nl, Nh     MD5_LONG
+	Data       [MD5_LBLOCK]MD5_LONG
+	Num        c.Uint
+}
+
+// OSSL_DEPRECATEDIN_3_0 int MD5_Init(MD5_CTX *c);
+//
+// llgo:link (*MD5_CTX).Init C.MD5_Init
+func (c *MD5_CTX) Init() c.Int { return 0 }
+
+// OSSL_DEPRECATEDIN_3_0 int MD5_Update(MD5_CTX *c, const void *data, size_t len);
+//
+// llgo:link (*MD5_CTX).Update C.MD5_Update
+func (c *MD5_CTX) Update(data unsafe.Pointer, n uintptr) c.Int { return 0 }
+
+func (c *MD5_CTX) UpdateBytes(data []byte) c.Int {
+	return c.Update(unsafe.Pointer(unsafe.SliceData(data)), uintptr(len(data)))
+}
+
+func (c *MD5_CTX) UpdateString(data string) c.Int {
+	return c.Update(unsafe.Pointer(unsafe.StringData(data)), uintptr(len(data)))
+}
+
+// OSSL_DEPRECATEDIN_3_0 int MD5_Final(unsigned char *md, MD5_CTX *c);
+//
+//go:linkname md5Final C.MD5_Final
+func md5Final(md unsafe.Pointer, c *MD5_CTX) c.Int
+
+func (c *MD5_CTX) Final(md unsafe.Pointer) c.Int {
+	return md5Final(md, c)
+}
+
+// OSSL_DEPRECATEDIN_3_0 unsigned char *MD5(const unsigned char *d, size_t n, unsigned char *md);
+//
+//go:linkname MD5 C.MD5
+func MD5(data unsafe.Pointer, n uintptr, md unsafe.Pointer) unsafe.Pointer
+
+func MD5Bytes(data []byte, md unsafe.Pointer) unsafe.Pointer {
+	return MD5(unsafe.Pointer(unsafe.SliceData(data)), uintptr(len(data)), md)
+}
+
+func MD5String(data string, md unsafe.Pointer) unsafe.Pointer {
+	return MD5(unsafe.Pointer(unsafe.StringData(data)), uintptr(len(data)), md)
+}
+
+// OSSL_DEPRECATEDIN_3_0 void MD5_Transform(MD5_CTX *c, const unsigned char *b);
+
+// -----------------------------------------------------------------------------
diff --git a/c/openssl/openssl.go b/c/openssl/openssl.go
new file mode 100644
index 00000000..cde02ca5
--- /dev/null
+++ b/c/openssl/openssl.go
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package openssl
+
+const (
+	LLGoPackage = "link: $(pkg-config --libs openssl); -lssl -lcrypto"
+)
+
+// -----------------------------------------------------------------------------