diff --git a/lualib-src/lua-crypt.c b/lualib-src/lua-crypt.c
index 6f99d4f6..77ba7c40 100644
--- a/lualib-src/lua-crypt.c
+++ b/lualib-src/lua-crypt.c
@@ -9,6 +9,10 @@
 #include <stdlib.h>
 #include <unistd.h>
 
+#define PADDING_MODE_ISO7816_4 0
+#define PADDING_MODE_PKCS7 1
+#define PADDING_MODE_COUNT 2
+
 #define SMALL_CHUNK 256
 
 /* the eight DES S-boxes */
@@ -353,6 +357,97 @@ lrandomkey(lua_State *L) {
 	return 1;
 }
 
+static void
+padding_mode_table(lua_State *L) {
+	// see macros PADDING_MODE_ISO7816_4, etc.
+	const char * mode[] = {
+		"iso7816_4",
+		"pkcs7",
+	};
+	int n = sizeof(mode) / sizeof(mode[0]);
+	int i;
+	lua_createtable(L,0,n);
+	for (i=0;i<n;i++) {
+		lua_pushinteger(L, i);
+		lua_setfield(L, -2, mode[i]);
+	}
+}
+
+typedef void (*padding_add)(uint8_t buf[8], int offset);
+typedef int (*padding_remove)(const uint8_t *last);
+
+static void
+padding_add_iso7816_4(uint8_t buf[8], int offset) {
+	buf[offset] = 0x80;
+	memset(buf+offset+1, 0, 7-offset);
+}
+
+static int
+padding_remove_iso7816_4(const uint8_t *last) {
+	int padding = 1;
+	int i;
+	for (i=0;i<8;i++,last--) {
+		if (*last == 0) {
+			padding++;
+		} else if (*last == 0x80) {
+			return padding;
+		} else {
+			break;
+		}
+	}
+	// invalid
+	return 0;
+}
+
+static void
+padding_add_pkcs7(uint8_t buf[8], int offset) {
+	uint8_t x = 8-offset;
+	memset(buf+offset, x, 8-offset);
+}
+
+static int
+padding_remove_pkcs7(const uint8_t *last) {
+	int padding = *last;
+	int i;
+	for (i=1;i<padding;i++) {
+		--last;
+		if (*last != padding)
+			return 0;	// invalid
+	}
+	return padding;
+}
+
+static padding_add padding_add_func[] = {
+	padding_add_iso7816_4,
+	padding_add_pkcs7,
+};
+
+static padding_remove padding_remove_func[] = {
+	padding_remove_iso7816_4,
+	padding_remove_pkcs7,
+};
+
+static inline void
+check_padding_mode(lua_State *L, int mode) {
+	if (mode < 0 || mode >= PADDING_MODE_COUNT)
+		luaL_error(L, "Invalid padding mode %d", mode);
+}
+
+static void
+add_padding(lua_State *L, uint8_t buf[8], const uint8_t *src, int offset, int mode) {
+	check_padding_mode(L, mode);
+	if (offset >= 8)
+		luaL_error(L, "Invalid padding");
+	memcpy(buf, src, offset);
+	padding_add_func[mode](buf, offset);
+}
+
+static int
+remove_padding(lua_State *L, const uint8_t *last, int mode) {
+	check_padding_mode(L, mode);
+	return padding_remove_func[mode](last);
+}
+
 static void
 des_key(lua_State *L, uint32_t SK[32]) {
 	size_t keysz = 0;
@@ -371,6 +466,7 @@ ldesencode(lua_State *L) {
 	size_t textsz = 0;
 	const uint8_t * text = (const uint8_t *)luaL_checklstring(L, 2, &textsz);
 	size_t chunksz = (textsz + 8) & ~7;
+	int padding_mode = luaL_optinteger(L, 3, PADDING_MODE_ISO7816_4);
 	uint8_t tmp[SMALL_CHUNK];
 	uint8_t *buffer = tmp;
 	if (chunksz > SMALL_CHUNK) {
@@ -380,18 +476,8 @@ ldesencode(lua_State *L) {
 	for (i=0;i<(int)textsz-7;i+=8) {
 		des_crypt(SK, text+i, buffer+i);
 	}
-	int bytes = textsz - i;
 	uint8_t tail[8];
-	int j;
-	for (j=0;j<8;j++) {
-		if (j < bytes) {
-			tail[j] = text[i+j];
-		} else if (j==bytes) {
-			tail[j] = 0x80;
-		} else {
-			tail[j] = 0;
-		}
-	}
+	add_padding(L, tail, text+i, textsz - i, padding_mode);
 	des_crypt(SK, tail, buffer+i);
 	lua_pushlstring(L, (const char *)buffer, chunksz);
 
@@ -413,6 +499,7 @@ ldesdecode(lua_State *L) {
 	if ((textsz & 7) || textsz == 0) {
 		return luaL_error(L, "Invalid des crypt text length %d", (int)textsz);
 	}
+	int padding_mode = luaL_optinteger(L, 3, PADDING_MODE_ISO7816_4);
 	uint8_t tmp[SMALL_CHUNK];
 	uint8_t *buffer = tmp;
 	if (textsz > SMALL_CHUNK) {
@@ -421,17 +508,8 @@ ldesdecode(lua_State *L) {
 	for (i=0;i<textsz;i+=8) {
 		des_crypt(SK, text+i, buffer+i);
 	}
-	int padding = 1;
-	for (i=textsz-1;i>=textsz-8;i--) {
-		if (buffer[i] == 0) {
-			padding++;
-		} else if (buffer[i] == 0x80) {
-			break;
-		} else {
-			return luaL_error(L, "Invalid des crypt text");
-		}
-	}
-	if (padding > 8) {
+	int padding = remove_padding(L, buffer + textsz - 1, padding_mode);
+	if (padding <= 0 || padding > 8) {
 		return luaL_error(L, "Invalid des crypt text");
 	}
 	lua_pushlstring(L, (const char *)buffer, textsz - padding);
@@ -954,6 +1032,7 @@ lxor_str(lua_State *L) {
 int lsha1(lua_State *L);
 int lhmac_sha1(lua_State *L);
 
+
 LUAMOD_API int
 luaopen_skynet_crypt(lua_State *L) {
 	luaL_checkversion(L);
@@ -980,9 +1059,14 @@ luaopen_skynet_crypt(lua_State *L) {
 		{ "hmac_sha1", lhmac_sha1 },
 		{ "hmac_hash", lhmac_hash },
 		{ "xor_str", lxor_str },
+		{ "padding", NULL },
 		{ NULL, NULL },
 	};
 	luaL_newlib(L,l);
+
+	padding_mode_table(L);
+	lua_setfield(L, -2, "padding");
+
 	return 1;
 }
 
diff --git a/test/testcrypt.lua b/test/testcrypt.lua
new file mode 100644
index 00000000..01038b7c
--- /dev/null
+++ b/test/testcrypt.lua
@@ -0,0 +1,24 @@
+local skynet = require "skynet"
+local crypt = require "skynet.crypt"
+
+local text = "hello world"
+local key = "12345678"
+
+local function desencode(key, text, padding)
+	local c = crypt.desencode(key, text, crypt.padding[padding or "iso7816_4"])
+	return crypt.base64encode(c)
+end
+
+local function desdecode(key, text, padding)
+	text = crypt.base64decode(text)
+	return crypt.desdecode(key, text, crypt.padding[padding or "iso7816_4"])
+end
+
+local etext = desencode(key, text)
+assert( etext == "KNugLrX23UcGtcVlk9y+LA==")
+assert(desdecode(key, etext) == text)
+
+local etext = desencode(key, text, "pkcs7")
+assert(desdecode(key, etext, "pkcs7") == text)
+
+skynet.start(skynet.exit)
\ No newline at end of file