package keygen;
 
import java.math.BigInteger;
import java.util.Date;
import java.util.zip.CRC32;
 
public class Keygen {
 
    private static final int version = 14;
 
    /**
     * @param s
     * @param i
     * @param bytes
     * @return
     */
    public static short getCRC(String s, int i, byte bytes[]) {
        CRC32 crc32 = new CRC32();
        if (s != null) {
            for (int j = 0; j < s.length(); j++) {
                char c = s.charAt(j);
                crc32.update(c);
            }
        }
        crc32.update(i);
        crc32.update(i >> 8);
        crc32.update(i >> 16);
        crc32.update(i >> 24);
        for (int k = 0; k < bytes.length - 2; k++) {
            byte byte0 = bytes[k];
            crc32.update(byte0);
        }
        return (short) (int) crc32.getValue();
    }
 
    /**
     * @param biginteger
     * @return String
     */
    public static String encodeGroups(BigInteger biginteger) {
        BigInteger beginner1 = BigInteger.valueOf(0x39aa400L);
        StringBuilder sb = new StringBuilder();
        for (int i = 0; biginteger.compareTo(BigInteger.ZERO) != 0; i++) {
            int j = biginteger.mod(beginner1).intValue();
            String s1 = encodeGroup(j);
            if (i > 0) {
                sb.append("-");
            }
            sb.append(s1);
            biginteger = biginteger.divide(beginner1);
        }
        return sb.toString();
    }
 
    /**
     * @param i
     * @return
     */
    public static String encodeGroup(int i) {
        StringBuilder sb = new StringBuilder();
        for (int j = 0; j < 5; j++) {
            int k = i % 36;
            char c;
            if (k < 10) {
                c = (char) (48 + k);
            } else {
                c = (char) ((65 + k) - 10);
            }
            sb.append(c);
            i /= 36;
        }
        return sb.toString();
    }
 
    /**
     * @param name
     * @param days
     * @param id
     * @return
     */
    public static String MakeKey(String name, int days, int id) {
        id %= 100000;
        byte bkey[] = new byte[12];
        bkey[0] = (byte) 1; // Product type: IntelliJ IDEA is 1
        bkey[1] = version;
        Date d = new Date();
        long ld = (d.getTime() >> 16);
        bkey[2] = (byte) (ld & 255);
        bkey[3] = (byte) ((ld >> 8) & 255);
        bkey[4] = (byte) ((ld >> 16) & 255);
        bkey[5] = (byte) ((ld >> 24) & 255);
        days &= 0xffff;
        bkey[6] = (byte) (days & 255);
        bkey[7] = (byte) ((days >> 8) & 255);
        bkey[8] = 105;
        bkey[9] = -59;
        bkey[10] = 0;
        bkey[11] = 0;
        int w = getCRC(name, id % 100000, bkey);
        bkey[10] = (byte) (w & 255);
        bkey[11] = (byte) ((w >> 8) & 255);
        BigInteger pow = new BigInteger("89126272330128007543578052027888001981", 10);
        BigInteger mod = new BigInteger("86f71688cdd2612ca117d1f54bdae029", 16);
        BigInteger k0 = new BigInteger(bkey);
        BigInteger k1 = k0.modPow(pow, mod);
        String s0 = Integer.toString(id);
        String sz = "0";
        while (s0.length() != 5) {
            s0 = sz.concat(s0);
        }
        s0 = s0.concat("-");
        String s1 = encodeGroups(k1);
        s0 = s0.concat(s1);
        return s0;
    }
}
 

摘自：http://inhu.net/intellij-idea-14-keygen.html