Java implementation of scrypt
 A pure Java implementation of the scrypt key derivation function and a JNI
 interface to the C implementations, including the SSE2 optimized version.
 The Java implementation is based in large part on Colin Percival's
 reference implementation contained in crypto_scrypt-ref.c, but any errors
 in this port are solely the fault of its author, Will Glozer.
 https://www.tarsnap.com/scrypt/scrypt.pdf
 https://scrypt.googlecode.com
 Join the lambdaWorks-OSS Google Group to discuss this project:
 http://groups.google.com/group/lambdaworks-oss
 lambdaworks-oss@googlegroups.com
Usage
 com.lambdaworks.crypto.SCryptUtil implements a modified version of MCF,
 the modular crypt format, similar to the one used for storage of Unix
 passwords in the MD5, SHA-256, and bcrypt formats.
 SCryptUtil.scrypt(passwd, N, r, p)
 SCryptUtil.check(passwd, hashed)
 The output of SCryptUtil.scrypt is a string in the modified MCF format:
 $s0$params$salt$key
 s0 - version 0 of the format with 128-bit salt and 256-bit derived key
 params - 32-bit hex integer containing log2(N) (16 bits), r (8 bits), and p (8 bits)
 salt - base64-encoded salt
 key - base64-encoded derived key
 Example:
 $s0$e0801$epIxT/h6HbbwHaehFnh/bw==7ドルH0vsXlY8UxxyW/BWx/9GuY7jEvGjT71GFd6O4SZND0=
 passwd = "secret"
 N = 16384
 r = 8
 p = 1
Native Code Implementation
 When the native library can be loaded it will be used instead of the pure
 Java implementation. On a J2SE compliant JVM the native library will be
 extracted from the jar and loaded, and on other VMs System.loadLibrary will
 be called.
 The system property "com.lambdaworks.jni.loader" may be set to override
 the default native library loader with one of the following values:
 nil: refuse to load native libraries and revert to pure Java implementation
 jar: extract native library from jar and load with System.load
 sys: use System.loadLibrary, which may require java.library.path to be set
Maven Artifacts
 Releases containing the pure Java implementation, as well as native libraries
 for a limited number of platforms, are available in the maven central repository.
 <dependency>
 <groupId>com.lambdaworks</groupId>
 <artifactId>scrypt</artifactId>
 <version>1.4.0</version>
 </dependency>
Building Native Implementation
 A native shared library for the current platform may be built by running GNU
 make. The Makefile attempts to detect the runtime platform and JDK location,
 but in some cases one or more of the following variables should be passed
 to make:
 TARGET - target operating system, use "android" to build for Android
 SSE2 - use the SSE2 optimized scrypt implementation when set
 JAVA_HOME - base directory of a Java 6+ JDK
 NDK_ROOT - base directory of Android NDK
 A precompiled native library for Android 2.3 running on ARM is located in
 src/android/resources/lib/arm5/libscrypt.so. If placed in an .apk file's
 lib/armeabi directory it will be automatically loaded.