diff --git a/CMakeLists.txt b/CMakeLists.txt
index bc91a81..c4481d6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,7 +15,7 @@ option(
 option(
 	USE_OPENSSL
 	"use openssl"
-	ON
+	OFF
 )
 option(
 	USE_GMP
diff --git a/common.mk b/common.mk
index 68b6ba0..9ea2c0d 100644
--- a/common.mk
+++ b/common.mk
@@ -101,7 +101,7 @@ ifeq ($(OS),mac)
     MCL_USE_GMP=0
   endif
 endif
-MCL_USE_OPENSSL?=1
+MCL_USE_OPENSSL?=0
 ifeq ($(MCL_USE_GMP),0)
   CFLAGS+=-DMCL_USE_VINT
 endif
diff --git a/readme.md b/readme.md
index 3b43772..60539b5 100644
--- a/readme.md
+++ b/readme.md
@@ -37,10 +37,10 @@ x86-64/ARM/ARM64 Linux, macOS and mingw64 are supported.
 
 ## Installation Requirements
 
-[GMP](https://gmplib.org/) and [OpenSSL](https://www.openssl.org/) are necessary (default setting).
+[GMP](https://gmplib.org/) is necessary (default setting).
 
 ```
-apt install libgmp-dev libssl-dev # on Ubuntu
+apt install libgmp-dev # on Ubuntu
 ```
 
 ## How to build with Makefile
@@ -72,16 +72,10 @@ make MCL_USE_GMP=0
 ```
 Define `MCL_USE_VINT` if using C++ header files.
 
-## How to build without OpenSSL
-
-```
-make MCL_USE_OPENSSL=0
-```
-Define `MCL_DONT_USE_OPENSSL` if using C++ header files.
 
 ## How to build on 32-bit x86 Linux
 
-Build GMP and OpenSSL for 32-bit mode and install `<lib32>` at yourself.
+Build GMP and for 32-bit mode and install `<lib32>` at yourself.
 
 ```
 make ARCH=x86 CFLAGS_USER="-I <lib32>/include" LDFLAGS_USER="-L <lib32>/lib -Wl,-rpath,<lib32>/lib"
@@ -90,7 +84,7 @@ make ARCH=x86 CFLAGS_USER="-I <lib32>/include" LDFLAGS_USER="-L <lib32>/lib -Wl,
 # How to build on 64-bit Windows with Visual Studio
 
 Clone cybozulib\_ext,
-which provides compiled binaries of OpenSSL and [MPIR](http://mpir.org/).
+which provides compiled binaries of [MPIR](http://mpir.org/).
 
 ```
 mkdir work
@@ -133,7 +127,6 @@ msbuild mcl.sln /p:Configuration=Release /m
 
 ```
 cmake .. USE_GMP=OFF ; without GMP
-cmake .. USE_OPENSSL=OFF ; without OpenSSL
 ```
 see `cmake .. -LA`.