wg/scrypt

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
[email protected]

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==$7H0vsXlY8UxxyW/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.

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.