使用RFC2898从密码生成密钥。据我所知,这不包含在 JRE 或 JCE 中,但它包含在JBoss、Oracle 和WebSphere等 J2EE 服务器中。它也包含在 .NET 基类库 ( Rfc2898DeriveBytes ) 中。
Java 中有一些 LGPL 实现,但快速浏览一下,这个实现看起来有点过于复杂。还有一个很好的javascript 版本。(我制作了该版本的修改版本并将其打包为 Windows 脚本组件)
由于缺乏具有适当许可证的良好实现,我从 Mattias Gartner 打包了一些代码。这是完整的代码。简短,简单,易于理解。它是根据MS Public License获得许可的。
// PBKDF2.java
// ------------------------------------------------------------------
//
// RFC2898 PBKDF2 in Java. The RFC2898 defines a standard algorithm for
// deriving key bytes from a text password. This is sometimes
// abbreviated "PBKDF2", for Password-based key derivation function #2.
//
// There's no RFC2898-compliant PBKDF2 function in the JRE, as far as I
// know, but it is available in many J2EE runtimes, including those from
// JBoss, IBM, and Oracle.
//
// It's fairly simple to implement, so here it is.
//
// Created Sun Aug 09 01:06:57 2009
//
// last saved:
// Time-stamp: <2009-August-09 02:19:50>
// ------------------------------------------------------------------
//
// code thanks to Matthias Gartner
//
// ------------------------------------------------------------------
package cheeso.examples;
import java.security.NoSuchAlgorithmException;
import java.security.InvalidKeyException;
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
public class PBKDF2
{
public static byte[] deriveKey( byte[] password, byte[] salt, int iterationCount, int dkLen )
throws java.security.NoSuchAlgorithmException, java.security.InvalidKeyException
{
SecretKeySpec keyspec = new SecretKeySpec( password, "HmacSHA1" );
Mac prf = Mac.getInstance( "HmacSHA1" );
prf.init( keyspec );
// Note: hLen, dkLen, l, r, T, F, etc. are horrible names for
// variables and functions in this day and age, but they
// reflect the terse symbols used in RFC 2898 to describe
// the PBKDF2 algorithm, which improves validation of the
// code vs. the RFC.
//
// dklen is expressed in bytes. (16 for a 128-bit key)
int hLen = prf.getMacLength(); // 20 for SHA1
int l = Math.max( dkLen, hLen); // 1 for 128bit (16-byte) keys
int r = dkLen - (l-1)*hLen; // 16 for 128bit (16-byte) keys
byte T[] = new byte[l * hLen];
int ti_offset = 0;
for (int i = 1; i <= l; i++) {
F( T, ti_offset, prf, salt, iterationCount, i );
ti_offset += hLen;
}
if (r < hLen) {
// Incomplete last block
byte DK[] = new byte[dkLen];
System.arraycopy(T, 0, DK, 0, dkLen);
return DK;
}
return T;
}
private static void F( byte[] dest, int offset, Mac prf, byte[] S, int c, int blockIndex ) {
final int hLen = prf.getMacLength();
byte U_r[] = new byte[ hLen ];
// U0 = S || INT (i);
byte U_i[] = new byte[S.length + 4];
System.arraycopy( S, 0, U_i, 0, S.length );
INT( U_i, S.length, blockIndex );
for( int i = 0; i < c; i++ ) {
U_i = prf.doFinal( U_i );
xor( U_r, U_i );
}
System.arraycopy( U_r, 0, dest, offset, hLen );
}
private static void xor( byte[] dest, byte[] src ) {
for( int i = 0; i < dest.length; i++ ) {
dest[i] ^= src[i];
}
}
private static void INT( byte[] dest, int offset, int i ) {
dest[offset + 0] = (byte) (i / (256 * 256 * 256));
dest[offset + 1] = (byte) (i / (256 * 256));
dest[offset + 2] = (byte) (i / (256));
dest[offset + 3] = (byte) (i);
}
// ctor
private PBKDF2 () {}
}