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synchronizing access to static variables

 
 
sosecret2006
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      12-26-2006
I copied and pasted some DES crypto code from the internet. I am trying
to transform the class to be more utility-based instead of having to
instantiate a copy each time. I am not great at Java threads. Can you
please examine the (small amount of) code below and tell me if the
synchronization is optimal? Please feel free to make any other comments
about how I can improve the class.

public final class DESCrypto {
private static final Log logger =
LogFactory.getLog(DESCrypto.class);
private static final String DES = "DES";
private static final String UTF8 = "UTF8";

private static final Cipher ecipher;
private static final Cipher dcipher;

private DESCrypto() {
throw new UnsupportedOperationException("do not use");
}

static {
try {
// load the stored key
InputStream keyis =
DESCrypto.class.getResourceAsStream("DESCrypto.key ");
ByteArrayOutputStream byteos = new ByteArrayOutputStream();
int b;
while ((b = keyis.read()) != -1) {
byteos.write(b);
}
SecretKey key = new SecretKeySpec(byteos.toByteArray(),
DES);

// to generate a new key, use:
// SecretKey key = KeyGenerator.getInstance("DES").generateKey();
// byte[] keyout = key.getEncoded();
// FileOutputStream keyfos = new
FileOutputStream("DesEncrypter.key");
// keyfos.write(keyout);
// keyfos.close();

// create and initialize ciphers
ecipher = Cipher.getInstance(DES);
dcipher = Cipher.getInstance(DES);
ecipher.init(Cipher.ENCRYPT_MODE, key);
dcipher.init(Cipher.DECRYPT_MODE, key);
} catch (Exception ex) {
logger.error(ex);
throw new RuntimeException(ex);
}
}

public static String encrypt(String str) {
try {
synchronized (DESCrypto.class) {
byte[] utf8 = str.getBytes(UTF;
byte[] enc = ecipher.doFinal(utf;
return new sun.misc.BASE64Encoder().encode(enc);
}
} catch (Exception ex) {
logger.error(ex);
throw new RuntimeException(ex);
}
}

public static String decrypt(String str) {
try {
synchronized (DESCrypto.class) {
byte[] dec = new
sun.misc.BASE64Decoder().decodeBuffer(str);
byte[] utf8 = dcipher.doFinal(dec);
return new String(utf8, UTF;
}
} catch (Exception ex) {
logger.error(ex);
throw new RuntimeException(ex);
}
}
}

 
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