/**
* Returns an instance of a padding algorithm given its name.
*
* @param prng the case-insensitive name of the PRNG.
* @return an instance of the pseudo-random number generator.
* @exception InternalError if the implementation does not pass its self- test.
*/
public static final IRandom getInstance(String prng) {
if (prng == null) {
return null;
}
prng = prng.trim();
IRandom result = null;
if (prng.equalsIgnoreCase(ARCFOUR_PRNG) || prng.equalsIgnoreCase(RC4_PRNG)) {
result = new ARCFour();
} else if (prng.equalsIgnoreCase(ICM_PRNG)) {
result = new ICMGenerator();
} else if (prng.equalsIgnoreCase(MD_PRNG)) {
result = new MDGenerator();
} else if (prng.equalsIgnoreCase(UMAC_PRNG)) {
result = new UMacGenerator();
} else if (prng.toLowerCase().startsWith(PBKDF2_PRNG_PREFIX)) {
String macName = prng.substring(PBKDF2_PRNG_PREFIX.length());
IMac mac = MacFactory.getInstance(macName);
if (mac == null) {
return null;
}
result = new PBKDF2(mac);
}
return result;
}
private IMac getMac(char[] password) throws MalformedKeyringException {
if (!properties.containsKey("salt")) {
throw new MalformedKeyringException("no salt");
}
byte[] salt = Util.toBytesFromString(properties.get("salt"));
IMac mac = MacFactory.getInstance(properties.get("mac"));
if (mac == null) {
throw new MalformedKeyringException("no such mac: " + properties.get("mac"));
}
int keylen = mac.macSize();
int maclen = 0;
if (!properties.containsKey("maclen")) {
throw new MalformedKeyringException("no MAC length");
}
try {
maclen = Integer.parseInt(properties.get("maclen"));
} catch (NumberFormatException nfe) {
throw new MalformedKeyringException("bad MAC length");
}
HashMap pbAttr = new HashMap();
pbAttr.put(IPBE.PASSWORD, password);
pbAttr.put(IPBE.SALT, salt);
pbAttr.put(IPBE.ITERATION_COUNT, ITERATION_COUNT);
IRandom kdf = PRNGFactory.getInstance("PBKDF2-HMAC-SHA");
kdf.init(pbAttr);
byte[] dk = new byte[keylen];
try {
kdf.nextBytes(dk, 0, keylen);
} catch (LimitReachedException shouldNotHappen) {
throw new Error(shouldNotHappen.toString());
}
HashMap macAttr = new HashMap();
macAttr.put(IMac.MAC_KEY_MATERIAL, dk);
macAttr.put(IMac.TRUNCATED_SIZE, new Integer(maclen));
try {
mac.init(macAttr);
} catch (InvalidKeyException shouldNotHappen) {
throw new Error(shouldNotHappen.toString());
}
return mac;
}